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Gardening Answers Knowledgebase

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PAL Questions: 854 - Garden Tools: 352 - Recommended Websites: 639


Keywords: Insect pests--Control, Trees--Diseases and pests, Pesticides

PAL Question:

What is the latest method of eradication for the mountain pine beetle, Dendroctonus ponderosae, that is rampant in western Canada?

View Answer:

In the northwestern U.S., Washington State University Extension's Forest Health Notes states that the focus has shifted from using pesticides to taking preventive measures:
Excerpt:
Control methods have shifted away from direct control (e.g. spraying, felling, burning) and towards prevention of outbreaks. This course of action was chosen after thoroughly exploring direct control measures for nearly a century and arriving at a simple conclusion: They don't work. It is possible to prevent infestation with penetrating sprays on individual, high value trees such as those in campgrounds and near houses, but they need to be applied before the tree is infected and the cost of such treatments is prohibitive for any large-scale application.
Once a mountain pine beetle outbreak begins to spread, it can be stopped by thinning the stand ahead of the edge of the outbreak. This is because outbreaks expand on a tree to tree basis where the incoming beetles switch their attacks from a recently attacked-stem to the next largest tree. More importantly, infestations can be prevented by thinning stands before crown closure, an operation that not only increases the vigor of the residual stand, but also prevents the spread of an outbreak if individual trees have been attacked.
Mountain pine beetles are a natural part of western ecosystems, and for this reason will never be completely eradicated (nor should they be, as they serve to create small stand openings which are important for biodiversity of both flora and fauna). As such, the death of a few trees on your property doesn't necessarily mean an epidemic is getting started; check your trees for root disease symptoms. To maintain mountain pine beetles at their normal levels, predisposing factors for outbreak must be removed. Some of these, such as environmental stresses, are not possible to control. However, many stresses are related to stand management practices. First and foremost, two situations need to be addressed: root disease centers and overstocked stands. More details about treatment for root disease centers have been given in other WSU Cooperative Extension "Forest Health Notes;" in summary, they need to be identified and planted with resistant species. Overstocking causes trees to compete for water, light and nutrients, and thus weakens their defenses against bark beetle attack. To minimize stand stresses and maintain vigorous growing conditions, stand managers should: (adapted from Berryman: Forest Insects, 1986).

Natural Resources Canada has a task force on the mountain pine beetle. You might want to contact them for the latest update. Go to their mountain pine beetle website and follow the links for additional information, including how to contact CCoFI.

Season All Season
Date 2007-12-06
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Keywords: genetically modified seeds, Weed control, Herbicides

PAL Question:

What can you tell me about the weed killer "Concern Weed Prevention Plus"?

View Answer:

This product is corn-gluten based, and it is not meant to work on weeds which are already growing, but on those which have yet to emerge (pre-emergent). Corn gluten meal has been promoted as an environmentally safer alternative to conventional herbicides, but there are still certain issues that bear considering. Research at Oregon State University showed that corn gluten meal did not prevent weed seed germination. Here is an excerpt from the study's findings:
"Corn gluten meal did not control any weeds in any trials under any circumstances over a two-year period. They found no evidence of pre- or post-emergence weed control in any of their trials. Because it contains 10 percent nitrogen, corn gluten meal proved to be a very effective fertilizer, causing lush, dense growth of turfgrass and of weeds in shrub beds."

Although corn gluten meal presents far fewer risks to human and animal health than conventional herbicide, a gardener who is attempting to use only organic methods might consider the source of the corn in these products, which is very likely to be genetically modified. A webpage no longer available from University of Wisconsin Master Gardeners addressed this question:
"Up to 60% of the commercial corn and soybeans in the United States is grown from GMO seed. Corn gluten sold as a preemergent herbicide may indeed contain GMO corn, but it has not yet been tested. Here's the twist. Corn gluten can reduce the need for traditional herbicides that have environmental side effects. It likely now contains GMO corn. It could be produced from non-GMO corn, but would likely be more expensive."

Washington State University professor of horticulture Linda Chalker-Scott has also written about "The Myth of Weed-Killing Gluten," and states that no research suggests this is an effective method of weed control in the Northwest. She recommends sub-irrigation, mulch, and soil solarization instead.

Season All Season
Date 2007-12-06
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Keywords: Arboretums and botanical gardens--Pacific Northwest, Arboretums and botanical gardens--Washington, Xeriscaping

PAL Question:

Where in Washington State can I find examples of public gardens designed to be drought-tolerant xeriscapes?

View Answer:

There are Master Gardener Demonstration Gardens around the state, such as Riverfront Park Demonstration Garden and others in Wenatchee. There is also a WaterWise demonstration garden in Woodinville.

There is a water-wise garden in the Bellevue Botanic Garden.

There is a native plant garden maintained by the Tacoma Garden Club at Point Defiance Park.

Seattle Tilth maintains several demonstration gardens, including the Good Shepherd Center in the Wallingford neighborhood in Seattle and Bradner Gardens Park at 29th Ave. S. and S. Grand Street, in south Seattle. While not exclusively xeriscapes, their gardens employ water-saving techniques.

Season All Season
Date 2007-12-06
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Keywords: Plant exchanges and donations, Paeonia, Seed exchanges

PAL Question:

Do you know of any plant and seed-sharing sites where I might find some peonies, for example? Or where I might post some stuff I have no place for?

View Answer:

Most reliable seed exchange programs require membership, but . . .

PEONIES:
If you are interested specifically in peony seeds, the American Peony Society and the Canadian Peony Society are excellent sources.

You might also consider contacting the Pacific Northwest Peony Society. They are fairly new (est. 1996) and might not have a seed exchange yet, but can be helpful with other information.

GENERAL:
The American Horticultural Society has an excellent seed exchange program (you must be a member to participate) for just about anything you could want.

DONATING PLANTS:
There are several places locally that list plants for donation.
Plant Amnesty has an Adopt-a-Plant program. Also, try the Pacific Northwest Garden Exchange at GardenWeb.

SEED LIBRARIES:
This is a relatively recent phenomenon and many cities now have such programs. Here are some examples:
King County Seed Lending Library
Northeast Seattle Seed Library

SOCIAL MEDIA:
There are groups on Facebook devoted to plant and seed exchanges. Be aware that not all of them are cautious about excluding aggressive or invasive species.

Season Winter
Date 2007-12-06
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Keywords: Pruning shrubs, Rhododendron

PAL Question:

I need to know what to do with a rhododendron that has grown too big. I want to keep it, since it is a bookend to another plant. Can I cut it back, and if so, how far and when? Will it be okay and continue to bloom if I cut it back? Could you suggest something and also suggest a really good book on care, etc., for rhodies?

View Answer:

For general care, quick information is available at

1) The American Rhododendron Society, click on "Need Help Growing Rhododendrons?"

2) The Seattle Rhododendron Society has a Rhododendron Care page

For more extensive information, there are scores of great books. A good one that includes specifics about rhodies is Cass Turnbull's Guide to Pruning (Cass Turnbull, 2004). Plant Amnesty, founded by Turnbull, also has information on pruning an overgrown rhododendron.

You can also select one by thumbing through the paperbacks available at (almost) all nurseries. Sunset Publishing and American Horticultural Society are reliable publishers.

As an aside, there were some ancient, neglected, potentially beautiful rhodies at my home. They were pruned slowly over 3 to 4 years and look great now. So, don't be shy!

Season All Season
Date 2007-12-06
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Keywords: Dahlia

PAL Question:

I need to find a photo of the eyes on a dahlia tuber.

View Answer:

There is good information on growing dahlias, including an image of the location of the eye on a tuber, at the website of the American Dahlia Society. To find the eye, locate the point on the shoulder, or crown, of the tuber from which the plant grows. The blog of Lynch Creek Dahlias has good description and illustrations:
"Keep in mind that every dahlia tuber, to be viable, must have at least one eye, which you'll see as tiny pointed protrusions on or near the neck of the tuber (the neck is the tuber's connection to the central part of the root mass)."

Season Fall
Date 2007-12-06
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Keywords: Flowering of plants, Seedlings--Transplanting, Germination, Brugmansia

PAL Question:

Can you give me specific directions on how to germinate Brugmansia seed and care for the seedlings. Also, at what age or size do these plants flower?

View Answer:

The following information is quoted from the book Brugmansia and Datura: Angels' Trumpets and Thorn Apples (by Ulrike and Hans-Geog Preissel, 2002, p. 74):

The fresh seed should be sown as early as possible, at temperatures between 64--79 F. Cover the seed with approximately 1/5 (.20) inch of humus, which must be kept wet.

The seed is relatively large and is pressed lightly into the hummus to ensure contact with the moist planting mix. Initially cover the seed box with a glass plate to provide optimal humidity. At temperatures around 68 F, the various species of Brugmansia germinate very differently. As a rule, germination takes between 10 and 20 days. The young seedlings can then be planted out directly into small containers.Young plants that are grown from seed go through an immature phase, easily recognized by the change in leaf shape. The plants do not reach flowering maturity until the end of this immature phase. The length of time before the first flowering varies with the species. On average, most Brugmansia flower for the first time when the plant is between 2.5--5 feet in size. If they are well cultivated, then they will usually reach this size in six to nine months.

Plants grown from seed can look very different. They differ not only in leaf shape and size, flower shape, color and size, but also in other traits, such as susceptibility to diseases or willingness to flower. The possibilities are almost endless and many interesting and valuable discoveries are undoubtedly waiting to be made....

Season All Season
Date 2006-12-14
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Keywords: Plant patents and registrations

PAL Question:

Is there a published list of patented plants?

View Answer:

I was not able to find an accessible list of patented plants from the U.S. Patent and Trademark Office, but their website does provide information about plant patents. They also have a bookstore which sells printed "Index of Patents" issued in a particular year. Individual plant breeders may list their patented and patent-pending plants, as this example from PlantHaven shows. The plant breeders Proven Winners also have several informative pages about plant patents.

Season All Season
Date 2007-12-06
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Keywords: Botanical nomenclature

PAL Question:

Is there an online resource for tracking updates in plant taxonomy?

View Answer:

You may not be able to find up-to-the-minute, late-breaking changes, but you can search by plant family, genus, or species in the following online resources which are considered authoritative on plants and their scientific names:

1. You can download the USDA's Complete Plant List. You can search for plants by scientific or common name here as well.

2. The GRIN database (also maintained by the USDA) offers several searching options and provides information on changes for each plant retrieved.

3. The International Plant Names Index also allows you to search for plants by scientific name; in addition, you can search for publications.

4. Here are two more name databases for plants in various parts of the world: Multilingual Multiscript Plant Name Database and Flora Europaea.

5. Missouri Botanical Garden's Tropicos website is another source of information on changes to plant names.

6. Here are two links to more information about taxonomy.

Kew Gardens has information about why plants change their names.

The Horticultural Taxonomy Group (HORTAX) was set up in 1988, with the objective of providing a forum for taxonomists and horticulturists in the British Isles who have an interest in the taxonomy and nomenclature of cultivated plants.

7. There is a journal called Taxon, available online to subscribers, and available to Miller Library patrons using the library's computers.

Season All Season
Date 2007-12-06
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Keywords: Lawns--Planting, Weed control, Lawns--Care and maintenance

PAL Question:

I am renovating a lawn that has been completely ignored for a long time--dandelions 3 per square foot, for example. I need to know if I should use something like weed-and-feed now to kill the 1000s of weeds and wait till spring to aerate, remove the top 1/2-inch of the lawn, fertilize and re-seed. Do I need to get on this before the first frost?

View Answer:

Regarding your questions about lawn renovation, I have found a few options for you:

1. If the weed-and-feed product is for pre-emergent weeds, this would not work on your lawn, which already has dandelions growing actively. If the product is post-emergent, it will kill the dandelions, but if you are planning to sow grass seed, you will need to wait before sowing (different products have different guidelines, so check the directions on the package carefully). According to The Lawn Bible (by David R. Mellor, 2003), you should also make sure that the herbicide will target the weeds you have. Do not spray in windy conditions, and only treat areas which need it.

Overuse of herbicide destroys valuable bacteria and insects in the soil, so prevention is the best: mow the lawn high, which will keep weeds from getting established, as they need light to thrive; don't scalp the lawn; water only when it is too difficult to press a screwdriver into the top 2 inches of the soil.

2. There are less toxic alternatives. Some sources say that corn gluten prevents weed seeds from sprouting. They must be wet to be activated. (It won't work on dandelions which are already thriving in your lawn.) Please note that subsequent research suggests corn gluten may be ineffective as a weed control method. See this Oregon State University study.

According to Ann Lovejoy's book, The Handbook of Northwest Gardening, corn gluten should be spread at a rate of 20 pounds per 1,000 square feet of lawn. Do this two or three times a year (in spring and fall, with a summer booster as needed). For ongoing weed suppression, apply it in small amounts whenever you pull up weeds (make a paste of corn gluten and water).

3. The Lovejoy book also has a recipe for fall lawn renovation:
a. Mow the existing grass as short as possible.
b. Spread 1 inch of clean crushed quarter-ten gravel (not pea gravel) evenly over the entire surface.
c. Spread 1 inch of compost over the gravel.
d. Top-seed with a regionally appropriate blend if the lawn is thin and spotty.
e. Wait 6-7 weeks before mowing again.

A criticism of weed-and-feed products is that they will add excessive amounts of phosphorus to your lawn, which will actually encourage weed growth once the herbicide breaks down.

The Northwest Center for Alternatives to Pesticides has good information about controlling dandelions without using weed-and-feed products (originally published in the Journal of Pesticide Reform, Fall 2001).

Washington Toxics Coalition has information on an overall approach to weed control and lawn care

Season All Season
Date 2007-12-06
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Keywords: Coffee, Compost

PAL Question:

I have a composting question: I work at a large hospital and would like to collect all of the used coffee grounds/filters from the countless pots throughout the hospital and use it (tons of it!) for compost. Could you create adequate compost with just coffee and probably straw to balance it?

View Answer:

The information below is quoted from an article by Bob Smith, Washington State University Master Gardener Program Manager, Thurston County, in The Gardener, Vol. 6, No. 4, Winter 1995-96):

"In 1995, three local coffee houses called WSU Extension in Thurston County [Washington] for advice on composting coffee grounds. With the exception of worm bin composting, we were unable to find much information. Our Master Composter and Master Gardener volunteers decided to experiment. They composted about 270 pounds of coffee grounds donated by local espresso bars. They fed roughly 60 pounds to worms while composting the rest in regular bins.

"If coffee grounds are not worms's food of choice, they certainly must be high on the list. In appreciation for a meal of ready-to-consume grounds, the worms produced excellent compost. Incorporate coffee grounds soon after brewing into your worm box. This reduced the possibility of the grounds souring and attracting pesky fruit flies.

"We also experimented by composting coffee grounds in three types of traditional bins:
1) an enclosed holding bin made of recycled plastic,
2) a three-level wire stacking bin, and
3) a large, round, wire holding bin. Our primary concern was whether the coffee grounds would attract pests.

"We incorporated the grounds over a four month period yet experienced only one problem: fruit flies showed up in the enclosed plastic bin almost immediately after we added coffee grounds. In open wire bins, the grounds tended to dry out quickly. Overall, though, we found coffee grounds easy to work with and satisfactory for composting.

"Coffee grounds have a carbon-to-nitrogen ratio of 20:1, roughly equivalent to that of grass clippings. After brewing, coffee grounds contain up to 2% nitrogen. For composting purposes, consider coffee grounds green material similar to grass clippings. For brown material, we used leaves and sawdust. In these trials, we used a formula of one part green material (coffee grounds alone or mixed with grass clippings) to two parts leaves, or four parts green material to one part sawdust."

In the Winter 2009 issue of Master Gardener, WSU Extension Horticulturist Linda Chalker-Scott recommends using a thin layer (half an inch or less) of coffee grounds as mulch, topping this with a thicker layer (4 inches) of coarser organic material such as wood chips. She also says that the optimal percentage of coffee grounds in total compost volume should be 10 to 20 percent, and no more. The pH of spent coffee grounds varies, and one cannot assume they are acidic.

Season All Season
Date 2007-12-06
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Keywords: Matteuccia, Ornamental ferns

PAL Question:

I have ostrich [deciduous] ferns [on the grounds I keep] and I was wondering if there is anything special that I should do for them for the winter. What I have been doing is putting ground up leaves in the bed, but beyond that, I'm not sure if there is anything else I should do.

View Answer:

Andrew MacHugh's book, The Cultivation of Ferns (1992) says the following (from p. 47):

"In autumn, a mulch of well-rotted leafmould, peat or bark chippings should be given to ferns planted in open sites. [...] In winter the fronds of deciduous ferns can be cut back to an inch above the crown. In areas subject to frost, the decayed fronds will provide some protection to the plant and should not be removed until the spring growth of new fronds shows signs of emerging."

Season Fall
Date 2006-02-26
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Keywords: Rhamnus purshiana, Pyrus, Nyssa, Hovenia, Oxydendrum arboreum, Cornus nuttallii, Malus, Crataegus, Native plants--Care and maintenance, Trees--Pacific Northwest, Quercus, Multipurpose trees, Prunus, Acer

PAL Question:

Can you recommend some tree species (deciduous) that can have wet feet but will also tolerate dry conditions in the summer? The recommendations should be trees that are not too messy (no cottonwoods or alders, please) and not too big. I would like to plant some trees near a swale in my yard - so they could be sitting in soggy ground during the winter.

View Answer:

Following is a list of possibilities, most of which come from Water Conserving Plants for the Pacific Northwest West of the Cascades (by the N.W. Perennial Alliance, 1993). The list includes only trees that 1) thrive in soils which are waterlogged in the winter, and, 2) grow to less than 40 feet tall.

ACER (maple):
A. buergeranum (trident maple)
A. campestre (field maple)
A. ginnala (Amur maple)
A. circinatum (vine maple)
CORNUS nuttallii (western dogwood)
C. douglasii (black hawthorn)
C. monogyna
C. phaenopyrum (Washington thorn)
C. x lavallei (Carriere hawthorn)
HOVENIA dulcis (Japanese raisin tree)
MALUS fusca (Pacific crab apple)
NYSSA sylvatica (black gum)
OXYDENDRUM arboreum (sourwood)
PRUNUS (prune/plum/cherry):
P. virginiana var. melanocarpa (chokecherry)
P. emarginata (bitter cherry)
PYRUS (pear):
P. communis (common pear)
P. pyrifolia (Chinese pear, sand pear)
QUERCUS (oak):
Q. acutissima (sawtooth oak)
Q. imbricaria (shingle oak)
RHAMNUS purshiana (cascara)

Season Winter
Date 2006-05-23
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Keywords: Color, Parrotia

PAL Question:

I have a Parrotia persica tree that has never developed the dramatic purple color that the Sunset Western Garden Book says it should have. Its leaves do turn gold in the fall. What nutrient is it missing? It gets full sun, and is at the top of a sloping area of lawn. I have wondered if the run-off could be leaching something from the soil.

Any suggestions?

View Answer:

According to this article in Fine Gardening online, Parrotia persica only has that purple color as the leaves emerge in spring:
"Reddish-purple when unfolding in spring, the leaves are a lustrous dark green in summer, and yellow to orange or scarlet in fall. Leaves hold their color for a long period. Older branches and trunks develop an exfoliating gray, green, white, and brown color that is a welcome asset in the winter garden. It grows successfully in Zones 4 to 8, tolerates sun and partial shade, and is easy to transplant. Often, vegetatively propagated forms offer more reliable fall color."

According to Dirr's Hardy Trees and Shrubs (Timber Press, 1997), there is some variability in the foliage color: "[...]the developing leaves are reddish-purple to bronze, maturing to lustrous dark green." I don't believe missing nutrients are the reason you are not seeing dramatic purple color but if you are concerned, you can do a soil test for any imbalances.

Season All Season
Date 2007-12-06
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Keywords: Mexican plants, Plant care, Deppea

PAL Question:

I have a plant, Deppea splendens, purchased through a special offer from Pacific Horticulture. It is a native of Mexico. This year (I've had it for about 2 years) it looks very healthy and has gotten quite a bit bigger. It is supposed to flower, but it has yet to do so for me. Any answers?

View Answer:

Deppea splendens is such a rare (previously almost extinct) plant that none of our standard sources have any cultural information. However, there was an article written about it in the April 2000 issue of Pacific Horticulture by Kathy Musial which mentions that it needs a frost-protected spot if it is to flower. The article recommends growing it in a container in colder regions so it may be brought into a sheltered area. Overly dry conditions will also cause the flowers to abort.

Excerpts from the article are included in University of British Columbia Botanical Garden's "Botany Photo of the Day" web page.

An article in UCLA Botanical Garden provides additional information about the plant.

Season All Season
Date 2007-12-06
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Keywords: Opuntia, Native plants--Washington, Cactaceae (Cactus family), Cactus

PAL Question:

Does the Opuntia fragilis in the Puget Sound carry a vernacular name of dune or shore prickly pear?

View Answer:

The most common vernacular name of the cactus Opuntia fragilis in Washington is brittle prickly pear. When I searched for dune or shore prickly pear, I found these common names connected with other species of Opuntia.

For more information about Opuntia fragilis, see the Washington Flora Checklist and the USDA Plant Profile.

Season All Season
Date 2007-12-06
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Keywords: Buchloe, Turfgrasses, Lawns

PAL Question:

I was interested in trying out buffalo grass (Buchloe dactyloides) 'Legacy' from High Country Gardens. I was wondering if you knew anyone who has tried growing it in the PNW (esp. Whidbey Island) and what they thought of its performance.

View Answer:

According to the Sunset Western Garden Book, buffalo grass is best suited to Sunset zones 1-3, 10, and 11. Whidbey Island is Sunset zone 5. While the Sunset book does not address 'Legacy' in particular, you may find that this grass is not the best choice for your location.

The Washington State Extension in Puyallup created a ranked list of good turf cultivars for Western Washington.

Additional information, from the Extension, about lawns. Note that there is an article about buffalo grass, but it is focused on whether that grass will do well in Central Washington, not Western Washington.

Season All Season
Date 2007-12-06
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Keywords: Zelkova, Xylosma, Thujopsis, Taxodium, Tamarix, Poa, Pennisetum, Casuarina, Baccharis, Festuca, Juglans, Alnus, Palms, Allergies

PAL Question:

What could cause sinus allergy symptoms every December?

View Answer:

According to Thomas Ogren's book, Allergy Free Gardening , the genera Alnus, Baccharis, Casuarina, Festuca, Pennisetum, Juglans, Poa, Tamarix, Taxodium, Thujopsis, Xylosma, Zelkova, and palm trees all produce pollen during December.

(Source: Ogren, T.L., Allergy-Free Gardening: The revolutionary guide to healthy landscaping , 2000, pp.262-265)

Also check out Allergy Free Gardening website. There are a number of articles article on low-allergy gardening listed.

Season Winter
Date 2007-04-02
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Keywords: Shade trees, Fast growing trees, Ornamental trees, Acer

PAL Question:

We are looking for a tree to plant in our backyard to provide some shade. We live in a location that gets lots of sun. We want something that will grow quickly, develop a canopy that we can walk under, will get approximately 20-30 feet tall, 15-20 feet wide, and not need a lot of water. Evergreen is probably out of the question. Any suggestions?

View Answer:

I think that your best bet may be a maple. Three maple species surfaced that meet your criteria of a quick growing, 20-30 feet tall tree with an equal or greater spread, that will do well in the sun.

--Acer circinatum, the vine maple (the only downside--this may be a bit shrubby for your landscape)
--Acer ginnala, the Amur maple
--Acer palmatum, the Japanese maple (you'll need to be choosy in order to find a cultivar that will reach 20-30 feet, but there are some that do. Additionally, A. palmatum will tolerate drier soils than A. circinatum.)

Sources:
The Pacific Northwest Gardener's Book of Lists , R. & J. McNeilan, 1997, p. 18, 27, 30.
Tree & Shrub Gardening for Washington and Oregon , A. Beck & M. Binetti, 2001, p. 244-249.
Trees & Shrubs for Northwest Gardens , J. A. Grant & C. L. Grant, 1990, p. 56-58.

Season All Season
Date 2006-05-23
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Keywords: Dendrobium, Orchids

PAL Question:

I have a couple of Dendrobium orchids, and one other that I don't know the name of. Both the Dendrobium have lost all their leaves, and I'm worried that they will die if they are not repotted soon. There is white fuzzy mold growing in the potting mix (which is just bark) of at least one of them, and I researched a little online and found that it is a common kind of snow white fungus (that may not be the right name) that is common to orchids in general.

I'm worried about root rot, and I'm wondering what I can do to try to revive these two orchids back to blooming. I read that soaking the roots in hydrogen peroxide can often help kill the fungus and then repotting thereafter can possibly revive them. What would you suggest for a repotting mix, and do you have any tips on reviving orchids once that have lost all their leaves?

The roots seem to still be intact, and do not appear to be rotted, as far as I can tell. I'm also wondering about good types of greenhouses/shelters to keep them in, as well as heaters to keep them a little warmer in the house -- they seem to be having a harder time with the 60 degree temperatures that my apartment tends to be. Any advice you could give would be great!

View Answer:

Some Dendrobium are deciduous, so your plants are likely acting exactly as they should. However, now that they've lost their leaves, you should restrict watering them through the winter, watering them only enough to keep them from shriveling, until flower buds form. Then, resume watering again. The species of Dendrobium that are deciduous require night temps of 50-55 degrees F during the winter.

Dendrobium grow well in Osmunda fiber, a potting medium, or bark if they are carefully staked, though they shouldn't be re-potted or divided until new growth starts. Also, Dendrobium with 4 or 5 shoots will grow well in a 4-5 inch pot, so you don't necessarily need to increase the pot size when you do re-pot your plants.

If you cut back on the water you give your Dendrobium through the winter, you shouldn't have to worry about root rot/fungi, especially if you repot them when new growth appears.

The advice above is taken from Home Orchid Growing (by Rebecca T. Northen, 1990, pp. 209-212).

Orchid Growing Basics (by G. Schoser, 1993, pp.40-45) shows some ways you can create a good place for orchids inside your home. For Dendrobium, placing the plants in a window with southern exposure, a grow light that will give them 12 hours of light each day, and humidity (Schoser recommends standing the pots on upsidedown flower pots in a tray of water) seem to be the most important considerations.

The Miller Library has many, many books on orchid growing.

Also, you might want to investigate the Northwest Orchid Society.

Season All Season
Date 2007-12-13
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Keywords: Thamnocalamus, Fargesia, Borinda, Screens, Bamboo

PAL Question:

I would like to have some bamboo planted in my backyard for privacy. However, I am uncertain as to which species will work the best. The planting area will be about 8 feet by 2 feet near a wooden fence. The area does get some sun but is mostly shady. I am looking for bamboo that is fast growing but not invasive. I want it to grow upwardly fast (no more than 30 feet) but I don't want it to invade my neighbor's property on the other side of the fence. Could you recommend at least three different bamboo species that would work for this area?

View Answer:

In the December 2005 issue of Horticulture magazine, local author Val Easton recommends a number of different clumping bamboos. (You should choose clumping rather than running bamboo for your privacy screen, as they will not be likely to invade your neighbor's property.)

Here are three recommendations from her article:
Borinda macclureana - hardy to USDA Zone 7 part sun, 12 - 20 feet tall
Fargesia robusta - hardy to USDA Zone 6, dense erect to 16 feet
Thamnocalamus tessellatus - hardy to USDA Zone 7 upright to 16 feet

You might try the following two nurseries for availability: the Bamboo Garden Nursery and Beauty and the Bamboo.

Season All Season
Date 2007-12-13
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Keywords: Continuing education, Potted plants, Container gardening

PAL Question:

I am going to create container plantings for some customers, and I wonder if you know the best source (book) for combining plants in containers. Also, where might I take a class in container planting?

View Answer:

The Miller Library has a large number of books in its online catalog on container planting, but here are a few which may be helpful to you:

Container Gardens by Number by Bob Purnell (Reader's Digest, 2004)
Contain Yourself by Kerstin Ouellet (Ball Publishing, 2003)
The Complete Book of Container Gardening edited by Alan Toogood (Quarto Publishing, 1991)
The Book of Container Gardening by Malcolm Hillier (Simon & Schuster, 1991)
A Practical Step-by-Step Guide to Complete Container Gardening compiled by Ideas into Print (Whitecap Books, 1997)

This booklist will give you an idea of the selection of books on the topic.

The Center for Urban Horticulture occasionally offers classes on container planting, as does Seattle Tilth.

Also, some local nurseries occasionally offer classes. One example is Swanson's Nursery.

Season All Season
Date 2007-12-13
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Keywords: Chaenomeles, Bonsai

PAL Question:

I was given a 40-year-old Quince bonsai tree and I would like to get some advice on taking care of it. I have a great book called, Bonsai Basics which has given me some insight as to how to take care of it, but I am looking for more information. I was also wondering about getting the tree repotted and the roots trimmed (which needs to happen very soon, as far as I can gather.) The roots have not been trimmed on this particular tree for about 3 years, and it has survived a pretty hard hit of insect and fungus pests.

View Answer:

The Puget Sound Bonsai Association has a website with useful information and links to other bonsai-related organizations and information. This is an active group with regular meetings, some lectures/workshops, and a good newsletter.

Nurseries such as Bonsai Northwest, a specialty nursery in South Seattle, often offer classes on bonsai care.

Season All Season
Date 2007-12-13
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Keywords: Pruning, Clematis

PAL Question:

There is a very large evergreen clematis starting to devour my detached garage. How far back can I cut this and when should I prune it back? It's one of the first early spring bloomers with white flowers, possibly armandii? But I am uncertain...I need help since I don't want to butcher it and lose it, but it needs a big haircut!

View Answer:

Clematis armandii does have the reputation for taking over the world. According to the American Horticultural Society's Practical Guide on clematis (Clematis, by Charles Chesshire, 1999), you can prune it AFTER is has finished flowering, which in Seattle, it normally does by the end of March. While this type of clematis can be pruned in late winter, it flowers on the previous year's wood, so pruning at that time may remove buds and prevent flowering that spring.

Step 1 - remove any dead, dying, damaged, or deranged shoots.
Step 2 - they suggest that no real pruning is necessary but you can cut it back to control its growth. But you do NOT want to cut it all the way back into old dark, woody growth. Prune directly above a pair of strong side shoots.
Step 3 - you will need to keep after it each year to avoid a build up of tangled growth.

Fine Gardening has an article by Lee Reich on pruning clematis here.

Season Spring
Date 2007-12-13
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Keywords: Transplanting, Rhododendron

PAL Question:

Some friends of mine just bought an old house with a huge rhododendron up against the house. It is at least 8 feet high and probably 10 feet wide. I did not dig around and there may be multiple shrubs growing next to each other. What are the chances of moving the rhody successfully? Should it be cut way back before hand? Any particular time of year for moving it?

View Answer:

Fortunately, rhododendrons are very likely to succeed in being transplanted. Most experts recommend fall as the best time to transplant. Spring or late winter is second best.

The real challenge is getting a large enough rootball. A five-to-six foot plant requires a rootball of about 3 feet in diameter.

Step 1- dig a 12-18 inches deep trench around the rootball.
Step 2 - under cut the rootball to sever the roots from the underlying soil. The most important roots are the small feeder roots, not the big old ones. You can use a steel cable with a tractor or you can use a shovel and digging iron and a lot of hard work. The rootball will probably be about 8 - 12 inches deep and 3 feet in diameter.
Step 3 - tilt it on its side and slide a piece of 1/2-inch plywood under the rootball and set the plant upright. Use the plywood to move the plant to its new location. (A tarp works, too, if you can get it underneath the rootball.)
Step 4 - dig a new hole 4 feet in diameter and deep enough so that the rootball is 1 inch higher than the depth of the hole. (Slightly above grade)
Step 5 - water well and mulch around the perimeter of the plant BUT keep the mulch at least 2 inch away from the trunk of the plant.

Newly transplanted plants need some tender care and especially need to be watered regularly, but not over watered.

There were no recommendations to cut the foliage back. But it is always ok to prune out dead, dying, diseased or deranged stems. This also means you can prune out twiggy growth.

This information comes from Success with Rhododendrons and Azaleas by H. Edward Reiley (1992).

Season Fall
Date 2006-02-16
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Keywords: Aleuria, Fungi

PAL Question:

I have several beautiful orange fungi growing in my two year old garden. They appear mostly between stepping stones (full sun) which have a deep underlay of gravel and sand, and also in a nearby bed which is semi-shady. Is this an indicator of an extreme soil condition that I should remedy? Where can I learn more?

View Answer:

Most likely, this mushroom is Aleuria aurantia, orange peel fungus or golden fairy cup. This species is widespread and common, often growing along roads or paths. It fruits from late fall to early spring.

It doesn't seem to be a problem for gardens....I would enjoy it as an added bit of fall color when it pops up in your garden.

Here is a link to a website in California with a nice picture and some information.

Season Winter
Date 2007-12-13
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Keywords: Native plants--Washington, Natural landscaping, Native plant gardening

PAL Question:

I'm looking for a good publication on plant communities for my area, Whatcom County in northwest Washington. We want to encourage plant communities that will do well here, and have about 5 acres to work with. Can you make a suggestion, please?

View Answer:

If you are interested in plants native to Washington, I recommend these two books:

Kruckeberg, Arthur R., Gardening with Native Plants of the Pacific Northwest, University of Washington Press, Seattle, 2nd edition, 1996.
Pettinger, April, and Brenda Costano, Native Plants in the Coastal Garden - A Guide for Gardeners in the Pacific Northwest , Timber Press, Portland, OR, revised edition, 2002.

The Washington Native Plant Society is also a good resource.

If you are interested in plants that will grow well in your area, but are not necessarily native to Washington State, please check out the Miller Library's booklist about gardening in the Pacific Northwest.

Season All Season
Date 2007-12-13
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Keywords: Shade-tolerant plants, Epimedium

PAL Question:

Can you recommend some Epimedium species and tell me what kind of conditions they prefer?

View Answer:

The resources I consulted say that most Epimedium prefer part shade, and most are evergreen. Some will tolerate a partly sunny site as long as the soil does not dry out.

Epimedium perralderianum has bronze leaves that turn green and last throughout the year. It blooms in March/April. Epimedium x rubrum prefers shade, so if your site is partly sunny, this might not be the ideal choice.

Collectors Nursery in Battleground, WA, also carries several varieties.

One gardening website, Paghat's Garden, has especially good information. The site developer recommends in particular the following varieties:
Epimedium x versicolor 'Sulphureum', or Yellow Epimedium - for its evergreen foliage
Epimedium grandiflorum 'Lilafee' - for quite striking lavender flowers and evergreen foliage

Richie Steffen, curator of the Elisabeth C. Miller Garden, is the author of "Epimediums" Queens of the Woodland" published in Pacific Horticulture, April 2008.

Season All Season
Date 2007-12-13
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Keywords: Insect pests--Control, Wildlife pests, Moles

PAL Question:

I live in Seattle and have, for the first time this fall, noticed dirt mounds on my property. These mounds tend to be located near patios/driveways, and are not in the sod. They are loamy, with no apparent holes, and are about three to five inches high. I wouldn't call them conical. There are no mole tunnels, and, as far as I can see, no bugs. The mounds are bigger than the little fine-grain mounds I have noticed in years past with small black ants crawling in them. Is there someone I can ask about what is causing these mounds, and if it is something to be concerned about? Could it be ants or mice?

View Answer:

From your description of the dirt mounds, it sounds as though the critter in your yard may be either a mole or a gopher. The easiest way to tell the difference is by the type of mound you have. Here is information on moles and pocket gophers from Washington Department of Fish and Wildlife's Living with Wildlife website.

Below is additional information from "Of Bugs and Blights" (in Balls and Burlaps, February 1988, pp. 4 and 14):

A gopher mound fans out from a hole near one edge of the mound. This hole remains plugged while the gopher is on the runway system. The gopher mound is relatively flat compared to the mole mound. Gopher mounds vary from 1 to 3 feet in diameter...several mounds often will be found together. They are not regularly found in a line as are mole mounds. The mole mound is somewhat conical and not much over a foot in diameter. The hole is not evident when you look at the mound. Push the soil aside and you will find it under the center of the mound. Each mound is connected with the other in a line by the moles' runway system.

According to the article quoted above, moles are more likely to be found in gardens in Western Washington than are gophers. We have the journal Balls and Burlaps in the Miller Library. The article discusses the problems and benefits of moles, as well as control methods.

I also consulted the Western Garden Problem Solver (Sunset Books, 1998) to see if I could identify your mound-maker. Ground squirrels leave their burrows open, so if your mounds show no opening, you probably don't have squirrels. Mole mounds appear volcano-like, with signs of soil excavation.

Here is a link to information on ants and their nests which you might look at to see if the images resemble the mounds of soil you are seeing.

Season All Season
Date 2007-12-13
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Keywords: Paulownia tomentosa, Woody plant propagation, Invasive plants

PAL Question:

How can I propagate a Paulownia tree?

View Answer:

Something to consider before propagating this tree is its invasive potential. Depending on your location, increasing the population of Paulownia trees may not be wise. The Plant Conservation Alliance includes Paulownia tomentosa on their "Least Wanted" list. If you are in King County in Washington State, you may be interested to know that the Center for Invasive Species shows this tree in its Early Detection and Distribution map.

Nevertheless, directions for propagation are available. Peter Thompson's book, Creative Propagation (2nd edition, Timber Press, 2005), states that Paulownia is best propagated by seed in the spring, or by semi-mature root cuttings laid horizontally just below the surface of the soil. I suggest that you think twice before propagating this tree.

Season All Season
Date 2007-12-13
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Keywords: Insecticidal soap, Citrus limon, Aphids

PAL Question:

My Meyer lemon has aphids all over it and has lost its leaves! I just brought it inside for the winter. What can I do?

View Answer:

The aphids were more than likely already there, even if not enough for you to notice, and once inside the warm(er) house they multiplied. Aphids do love citrus plants. The blossoms probably fell off due to the temperature change they experienced coming indoors.

The following information was found on p. 278 of the 2001 edition of the Sunset Western Garden Book:

Citrus in containers. Fertilize monthly from midwinter to mid-autumn with high-nitrogen liquid fertilizer, containing chelated zinc, iron, and manganese. Potted citrus ... in cold-winter regions: shelter plants in winter; a cool greenhouse is best, but a basement area or garage with good bright light is satisfactory.

Many of the common products sold in nurseries or garden centers contain the trace elements listed in the Sunset info above. Also, there are specific formulations for citrus available, also carried by many nurseries and garden centers.

...Sunset Western Garden Book continued...Citrus as houseplants. No guarantee of flowering or fruiting indoors, though plants are still appealing. 'Improved Meyer' and 'Ponderosa' lemons [other citrus names omitted] are most likely to produce good fruit. Locate no farther than 6 ft. from a sunny window, away from radiators or other heat sources. Ideal humidity level is 50 percent. Increase moisture by misting tree; also ring tree with pebble-filled trays of water. Water sparingly in winter...

I grow 2 Meyer lemons and find that they do best outside until the temperature goes down into the 20s. They are pretty hardy. The aphid problem is not a problem outside until spring. If you have a sun porch at your house, that might be a great place to put the lemon in winter.

As for the aphids, Colorado State University Extension provides information on insect control using insecticidal soap. You can purchase it or make your own: 1 teaspoon of soap (the mildest you can find) per quart of water, sprayed on both sides of the leaves and on growing surfaces.

Season All Season
Date 2007-12-13
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Keywords: Winter gardening, Irrigation

PAL Question:

Can you tell me, what's the deal with watering in winter? I've heard that foundation plants which don't catch the rain under the eaves must be watered even in wintertime. Someone else says that watering anything in winter subjects it to freezing. Now I'm in a quandary. I don't want my plants to freeze to death, nor do I want them to die of dehydration. So what's the answer?

View Answer:

According to Colorado State University Extension, you do need to water if there has not been snow or rain. You should water when the temperature is above freezing and the soil is not frozen. You should water early in the day so that the water can soak in before it gets cold overnight and freezes.

Here in the Puget Sound area we do not have freezing temperatures very often so you should go ahead and water, especially those plants under the eaves.

Season Winter
Date 2007-12-13
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Keywords: Sarcococca, Soil compaction, Soil testing, Katsura

PAL Question:

I have some dying Katsura trees. I created a dry stream to one side of them to redirect water (they don't like wet roots). The owner has put 1-2 inches compost/soil down for some good nutrition and a few tree stakes into the area. There is also landscape fabric (the gray kind rain can get through) and another inch of bark to stop a horsetail problem that creeps in every year.

I am wondering if the the soil around the tree roots has become compacted by rains and is prohibiting the trees from getting oxygen through their roots. The yellow is not in leaf veins like an iron deficiency usually looks; it is almost as if the plant is getting its chlorophyll drained from inside. No bugs present to my knowledge either. I would like to know both what I might do about the soil and about the trees.

View Answer:

Some solutions to the problem may be to take some dead branches or stems to a Master Gardener clinic and ask them to help you identify what could be happening. You may also want to check that the compost is not closer than 4 inches from the trunk of the trees. If it is, scrape it away. For further evaluation of the soil, take a sample from around the tree and send it to a lab for analysis. Our website has a Soil Testing Information section that includes a list of labs that do soil test analysis. Check the area for drainage by digging a hole and filling it with water or let the rain do it and then see how long it takes to drain away. Perhaps you have a layer of hardpan clay underneath the trees that is blocking the drainage in winter and preventing the water from getting to the roots in summer.

A great resource on Katsura trees (Cercidiphyllum japonicum) is Dirr's Hardy Trees and Shrubs: An Illustrated Encyclopedia by Michael A. Dirr. The author notes that the tree requires ample moisture in the early years of establishment. From the book, Trees and Shrubs for Pacific Northwest Gardens, by John A. Grant and Carol L. Grant, Katsura trees prefer deep soils and adequate summer moisture. There is a Katsura planted in the Arboretum on the edge of a pond in soil that is permanently wet and it is doing just fine.

Season All Season
Date 2007-12-13
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Keywords: Rosa, Planting time, Planting

PAL Question:

When should I plant bare root roses?

View Answer:

The Seattle Rose Society suggests planting in March. The roses should be stored in a cool dark place if they cannot be planted right away.

Other recommendations include soaking the roots before planting (8-12 hours), and trimming off damaged or diseased roots. Try to maintain 3-5 canes per plant, and prune back to 3-5 buds per cane.

Dig a hole wide and deep enough to accommodate the roots. Make a cone-shaped mound of soil in the center of the hole to support the plant. Fill the hole 2/3 full of soil and add water to make a slurry--this gets between the roots. Do not tamp the soil. When the water drains, add more soil and repeat the water fill process until you reach the original soil surface (ground level).

Season Winter
Date 2007-12-13
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Keywords: Plant varieties, Fagus, Ornamental trees

PAL Question:

Can you give me a list of purple beech cultivars?

View Answer:

There are several Fagus sylvatica varieties with purple foliage:

'Atropunicea' (copper beech, purple beech) alt. 'Riversii' or 'Purpurea' - 50-60 feet tall, 35-45 feet wide; good in containers
'Dawyck Purple' - columnar to 70 feet tall and 15 feet wide
'Purpurea Pendula' (weeping copper beech) - usu. no more than 10 feet tall and wide; good in containers
'Red Obelisk' - columnar

Source: Western Garden Book, Sunset Publishing Corporation, 7th edition, 2001, p.347.

And from Paghat, the website of a Seattle area gardener:
F.sylvatica 'Black Swan' - swan neck growth habit
F.sylvatica 'Rohani'

Season All Season
Date 2006-02-16
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Keywords: Sciadopitys verticillata, Conifers--Propagation

PAL Question:

How can I propagate a Japanese umbrella pine?

View Answer:

Peter Thompson's book, Creative Propagation (Timber Press, 2nd ed., 2005), states that Sciadopitys verticillata can be propagated by seed or by cuttings (the latter method in autumn, early winter, or early spring). Seeds will grow into the form inherited from the parent trees; cuttings vary. On page 153 of his book, Thompson says that the cuttings can be taken from almost any part of the plant, but he recommends using cuttings from the leader shoot in order to get a symmetrical tree with an upright leader.

An article entitled Growth Response of Umbrella Pine as Influenced by Temperature, Photoperiod and Chilling (Journal of Environmental Horticulture, December 1985) discusses propagating Sciadopitys from seed.

There is information on propagation which comes from the USDA Forest Service National Seed Lab's profile of Sciadopitys verticillata (no longer available online). Here is an excerpt:

"The seeds should be sown in the fall or stratified for sowing in the spring. Umbrella-pine is not easy to grow and is extremely slow-growing when propagated from seed (Halladin 1991). It has a tendency to form several leaders. Field planting has been done with 3+2 and 4+2 stock (Dallimore and Jackson 1967). Umbrella-pine can also be propagated by layers or by cuttings of half-ripened wood in summer (Bailey 1939). A nursery in Oregon propagates solely by cuttings because of faster results; Halladin (1991) describes the technique in detail."

Season All Season
Date 2006-02-16
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Keywords: Plant care, Zamioculcas, Palms

PAL Question:

What are the cultural requirements for Zamioculcas?

View Answer:

Zamioculcas is in the plant family Araceae, and its common name is the Aroid palm. According to the Sunset Western Garden Book (2007), this tropical African perennial which resembles a cycad or a palm will grow slowly to 4-5 feet high by 3-4 feet wide. Grown outdoors, it prefers partial to full shade, but indoors you should provide bright filtered light. It should be placed on a tray of moistened pebbles, and misted occasionally. During active growth, keep the soil evenly moist, and give it balanced fertilizer once a month. During the fall and winter months, do not fertilize, and only water when the top inch of soil becomes dry. In summer, the plant may be moved outside to a shady spot. All parts of this plant are poisonous.

You can find discussion among growers of Zamioculcas zamiifolia (sometimes called "the ZZ plant") on the University of British Columbia Botanical Garden Forum.

Season All Season
Date 2007-12-13
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Keywords: Native plants--Washington, Calocedrus, Quercus

PAL Question:

Is incense cedar native to Washington state? And is the Garry oak native to Kitsap County, Washington?

View Answer:

Although incense cedar, Calocedrus decurrens, grows in Washington State, it is not native. According to the Sunset Western Garden Book (2001), incense cedar is native to south and central Oregon, California, western Nevada, and northern Baja California.

The Washington Native Plant Society does not include Garry oak, Quercus garryana, on their list of plants native to Kitsap County, but this tree will grow there.

A list of plants native to Kitsap County

More information on Garry oak at this link

Both of these links are part of the Washington Native Plant Society website.

Season All Season
Date 2006-12-08
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Keywords: Petroselinum, Biennials, Herbs

PAL Question:

Is Italian parsley a perennial or a biennial?

View Answer:

The Sunset Western Garden Book says that parsley (Petroselinum species) is a biennial grown as an annual.

University of Arkansas Extension provides additional information on growing parsley, including the Italian variety, which is Petroselinum neapolitanum, and curly leaf parsley, Petroselinum crispum.

Season All Season
Date 2007-12-13
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Keywords: Flower arrangement

PAL Question:

What is the right proportion of cut flowers to create a nice arrangement in a vase? Can you give me some other suggestions about flower arranging?

View Answer:

The National Association of Flower Arrangement Societies website lets you look at selections from their journal, online. Fusion Flowers magazine also has information online.

The Miller Library also has many books about flower arranging, two of which I've listed below:
Flower Arranging from the Garden (1989), by Daphne and Sid Love
The Complete Guide to Flower Arranging (1995), by Jane Packer

Season All Season
Date 2007-06-14
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Keywords: Hummingbirds, Gardening to attract birds

PAL Question:

What do hummingbirds eat? I want to attract them to my yard.

View Answer:

According to the Hummingbird Society, hummingbirds primarily eat nectar from flowers. They also eat small insects and spiders as sources of protein. For more information on their needs, see the website of the Hummingbird Society.

The City of Bellingham has a helpful guide to attracting hummingbirds which includes a list of plants which are nectar sources. Rainyside Gardeners also has a list of nectar plants for hummingbirds in the Pacific Northwest. Oregon State University Extension's "Attract Hummingbirds to Your Garden" by J. Olson and N. Allen is also a good starting point.

The Miller Library has many books about creating a hummingbird garden, including a book published by the Brooklyn Botanic Garden that provides lists and descriptions of plants that attract hummingbirds, arranged by geographic region (Hummingbird Gardens, 2000, edited by Stephen W. Kress).

Season All Season
Date 2007-12-13
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Keywords: Continuing education

PAL Question:

Do you know of any correspondence courses concerning landscape design criticism and critique?

View Answer:

There is a book called North American Horticulture--A Reference Guide, compiled by the American Horticultural Society (second edition, 1992, edited by Thomas M. Barrett). The book includes a chapter on education, including correspondence courses.

Three community colleges in the Puget Sound area offer horticulture degrees, and they might know something about correspondence programs. They are Edmonds Community College Horticulture and South Seattle College Horticulture, and Lake Washington Institute of Technology.

More colleges and universities are offering online courses now. Here are two examples :

Season All Season
Date 2008-01-03
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Keywords: Periodicals

PAL Question:

Are there any gardening magazines with practical information that is specific to the Pacific Northwest?

View Answer:

There are numerous newsletters and small magazines from Northwest organizations like Seattle Tilth, Plant Amnesty, and Washington Park Arboretum. There are relatively few mainstream magazines that only discuss PNW gardening issues. Here are two which are published in British Columbia that you might try:

GardenWise (B.C.)
Gardens West (B.C.)

Feel free to come into the Miller Library and browse our periodicals collection, which includes the newsletters and magazines listed above.

The Miller Library website has many links to online resources, many of which are Pacific Northwest-specific. For example, you can find local organizations and plant societies, as well as websites specific to gardening in our region. Look at the Resources page on our website for booklists and recommended links.

Season All Season
Date 2008-01-03
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Keywords: Chrysanthemum

PAL Question:

I've been trying to contact someone about growing cascading mums in the Pacific NW. I'm wondering if this region is appropriate to start a new hobby for myself. Is there a group (or individual) that you could refer me to?

View Answer:

There is a chapter of the National Chrysanthemum Society in Washington State. This link provides contact information for the WA chapter.

In my research about cascading chrysanthemums, I learned that the major species used is Chrysanthemum x morifolium, also known as Florists' Chrysanthemum. According to the Sunset Western Garden Book, this type of chrysanthemum will grow in Sunset zones 2-24; Seattle is zone 5.

Season All Season
Date 2008-01-03
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Keywords: Goats, Blackberries, Weed control--Pacific Northwest

PAL Question:

I am wondering about an environmentally sensitive way to get rid of blackberries. I understand that mowing them consistently for 4 years works, but unfortunately this is not an option because of the terrain. If an herbicide is our only option, can you recommend one that has minimal impact? The area is quite large - a mile long and 20 feet wide.

View Answer:

Invasive.org has produced a document entitled Controlling Himalayan Blackberry in the Pacific Northwest. It includes manual removal, shading, grazing, biological controls, and last-resort herbicide information. (We cannot recommend any specific herbicides, as we are not licensed pesticide handlers.)

The Northwest Coalition for Alternatives to Pesticides has information on nonchemical blackberry control.

For additional information, phone the Master Gardener's DialExtension (King County) at 206-296-3425 (or 800-325-6165, ext.6-3425) and listen to tape #1274 about removing blackberries. However, the solutions given in this tape may apply to smaller areas, rather than the larger stand you mentioned.

An interesting idea that some people are trying locally is the use of goats. This article in the Seattle Post-Intelligencer mentions Healing Hooves of Spokane. There is at least one company on Vashon Island which offers this service as well. Another P-I article mentions Rent-a-Ruminant.
This document from Sound Native Plants contains contact information for several such services.

Season All Season
Date 2008-01-03
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Keywords: Sustainable horticulture, Trifolium, Pisum, Vicia, Cover crops, Legumes

PAL Question:

I have two raised garden beds (8 x 12 feet) in my back yard. Recently I read somewhere that having a cover crop during our wet winter months would help decrease the leaching of nutrients and would also help bind nitrogen in the soil. Three suggested cover crops were crimson clover, Australian field peas (did they mean Austrian winter peas?), and vetch. What would you suggest? Are these good recommendations? Which might be the best?

View Answer:

Sustainable Horticulture: Today and Tomorrow (R. Poincelot, 2004, p. 372-377), says, "Cover crops, when managed as green manures, can supply considerable nitrogen for [vegetable] crops."

Legumes, like the pea and vetch you mentioned are good choices for increasing the nitrogen level in soils. (Hairy vetch, Vicia villosa, and Austrian winter pea, Pisum arvense). Crimson clover (Trifolium incarnatum) is almost as efficient at supplying nitrogen to the soil.

Hairy Vetch supplies 33-145 lb of nitrogen per acre/year to soil, Austrian winter pea supplies 53-100 lb/acre/year, and Crimson clover supplies 19-114 lb/acre/year.

Another species you might consider as a cover crop is Fava bean (Vicia faba), which supplies 25-105 lb/acre/year.

Additional information about growing cover crops in the Pacific Northwest can be found on Ed Hume's website.

Territorial Seed Company, in Oregon, sells small quantities of cover crop seed by mail order, including Hairy vetch, Crimson Clover, and Fava Bean.

Season Fall
Date 2008-01-03
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Keywords: Senna, Cassia, Rubus, Bible plants

PAL Question:

I am looking for more information regarding Rubus sanctus, also known as the Burning Bush at Saint Catherine's Monastery in the Sinai. I am interested in this plant because my church group is just finishing up our study of the Book of Exodus. And I thought this plant might make a really nice and symbolic gift. I am beginning to understand that this plant may be rare, or possibly known by another name?

View Answer:

The problem with English common names for plants of the Bible is that you are at several removes from knowing which plant the original Hebrew text describes. There are some sources which state that "burning bush" refers to Rubus sanctus, but it is more likely that it refers to Senna alexandrina. The Hebrew word in Exodus is sneh, which is the same as the Arabic word for the Senna plant.

Plants of the Bible by Michael Zohary (Cambridge University Press, 1982) says that "the plant in question, specifically named 'sneh,'might well have been a real plant in the local flora. As there is no hint in the text that the sneh was a thorny bush, and there are no plants in Sinai or anywhere else that are not consumed when burnt, sneh may be identified linguistically only." He also suggests that the plant may have been Cassia senna, now renamed Senna alexandrina. There is no native Rubus in Sinai, Egypt, or southern Israel, and the bramble in the monastery garden at Santa Caterina is a cultivated specimen, planted by the monks "to strengthen the belief that the 'burning bush' has grown there since the revelation, so completely is sneh equated with brambles in the minds of scholars and Bible lovers.

While Senna alexandrina may be a bit difficult to obtain, there are other species of Senna more widely available. However, if you wish to grow the Rubus you saw (now referred to as Rubus ulmifolius ssp. sanctus) as a keepsake from your trip to the monastery, you should go ahead.

Season All Season
Date 2008-01-03
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Keywords: Taxus brevifolia, Poisonous plants

PAL Question:

Is our native yew tree poisonous?

View Answer:

Taxus brevifolia, Pacific or Western yew, is native here. The Sunset Western Garden Book (2001, p.628) says that Taxus fruit, seeds, and foliage are poisonous if ingested.

Plants of the Pacific Northwest Coast by Pojar and Mackinnon (Lone Pine, 2004) says that "Western yew seeds are poisonous and humans should avoid the fleshy 'berries,' although a wide variety of birds consume them and disperse the seeds. The foliage is poisonous to horses and cattle."

The Plants for a Future database has more information at this link.

Season All Season
Date 2008-01-03
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Keywords: Irrigation water quality

PAL Question:

Are there any adverse effects from using fluoridated water in the garden?

View Answer:

I do know that some indoor plants do better with water that is not fluoridated. There are conflicting opinions on the effects of fluoride on human health and the environment (including plants). According to this 2004 article entitled Water fluoridation and the environment by Howard Pollick in the International Journal of Occupational Health (reprinted by the Centers for Disease Control), the fluoride level in residential water (as opposed to industrial runoff) seldom rises above a level of concern for plants.

For an alternate viewpoint, see the Fluoride Action Network's website. Washington Toxics Coalition has a brief article on fluoride in drinking water in their Spring 2007 Alternatives newsletter. (Scroll down to page 8.)

Season All Season
Date 2008-01-03
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Keywords: Geranium, Fertilizers

PAL Question:

What would be the best fertilizer for hardy geraniums and when?

View Answer:

Established hardy geraniums do not need much more than an application of compost in spring. Most commerical fertilizers will provide too much nitrogen, causing weak growth that flops over or needs staking. (Source: The Gardener's Guide to Growing Hardy Geraniums, by Trevor Bath, 1994)

Season All Season
Date 2006-02-26
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Keywords: Plant longevity, Osmanthus

PAL Question:

What is the lifespan of Osmanthus? A client's 20-year-old, 12 ft. tall shrubs were once a hedge that one was unable to see through, but have become a walk-through wall these past couple of years.

View Answer:

According to SelecTree, a database produced by the Urban Forest Ecosystems Institute, most Osmanthus species have a longevity of 50 up to 150 years. A plant's lifespan varies, and urban trees and shrubs tend to be subjected to more interventions in the form of pruning, pollution, damage from construction, and so on. Also, the hedge has undoubtedly become woody with age.

Season All Season
Date 2008-01-03
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Keywords: Berberis, Skimmia, Leucothoe, Fatsia, Euonymus, Elaeagnus, Multipurpose shrubs, Shade-tolerant plants, Osmanthus, Aucuba, Viburnum, Prunus, Camellia, Buxus

PAL Question:

Can you suggest some shade shrubs/low trees that could be used in the bottom quarter of a huge, years-old pile of yardwaste and branches that is now a 20 foot cliff? I have started with some vinca minor in the lower part but could use some ideas of some things to plant that might get 15 feet tall, evergreen, and grow in woods/shade or sun through trees.

View Answer:

The closest list I could find to meet your needs is one of evergreen shrubs that will grow in shade:

Japanese aucuba - Aucuba japonica vars.
common boxwood - Buxus sempervirens
camellia - Camellia sp.
gilt edge silverberry - Elaeagnus x ebbingei 'Gilt Edge'
Euonymus - Euonymus fortunei radicans
Japanese aralia - Fatsia japonica
drooping Leucothoe - Leucothoe fontanesiana
Oregon grape - Mahonia aquifolium
Burmese mahonia - Mahonia lomariifolia
longleaf mahonia - Mahonia nervosa
holly leaf osmanthus - Osmanthus heterophyllus vars.
English laurel - Prunus laurocerasus 'Mount Vernon'
Japanese skimmia - Skimmia japonica
evergreen huckleberry - Vaccinium ovatum
nannyberry - Viburnum lentago

Source: The Pacific Northwest Gardener's Book of Lists, by R. & J. McNeilan, 1997, p. 46-47

Season All Season
Date 2006-07-18
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Keywords: Prunus lusitanica, Growth

PAL Question:

My customer says his Portuguese laurel which is now a 5 foot tree won't be growing any bigger. It is in the shade, but don't these get 15 feet in height?

View Answer:

SelecTree, the website of the Urban Forest Ecosystems Institute, says that Portugal Laurel (Prunus lusitanica)will do well in sun to partial shade, and may grow up to 35 feet tall, at a rate of two feet a year.

The Sunset Western Garden Book (2001) says that a multi-trunked tree can get as large as 30 feet high and 30 feet wide. Perhaps your customer is expressing wishful thinking, and aspires to grow a shrub rather than a tree. Some people do grow it as a hedge, and clip it frequently to control its size.

Season All Season
Date 2008-01-03
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Keywords: Perennials--Care and maintenance, Iris

PAL Question:

Do I leave my Siberian iris alone through the winter, then cut them back in the spring when new growth starts to show, as I've done in the past, or do I cut them back now? My neighbor has had hers cut back for months now and insists her way is best...

View Answer:

According to the book The Siberian Iris, by Currier McEwen, 1996, you should "allow leaves to remain on the plants as long as they are green and adding energy to the plant through photosynthesis. When they turn brown in the fall, cut them off as low as possible and burn them.* It is risky to add them to the compost pile, as they may carry fungal spores, insect eggs, and other disease agents.

*Or put them in your trash (in a sealed bag).

Season Fall
Date 2008-01-03
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Keywords: Greenhouses

PAL Question:

We are currently making plans to construct a Plant Science Laboratory at our school, a community college in Seattle. The plans are to have a two greenhouses, gutter connected and providing about 1,800 square feet of space. It will be constructed on a 10,000 square feet of property near the school.

I am wondering if there are any publications that discuss the management of an educational greenhouse at the CUH library. Also, are there any newsletters, websites or other materials you are able to recommend?

View Answer:

The bulk of our books on greenhouses focus on either commercial growing or home hobbyist. We have some back issues of the journal GM Pro, also known as Greenhouse Management and Production, which has a commercial focus.

I searched the Garden Literature Index (of journals) and didn't find anything too promising on actual management. I recommend you try talking with some of your colleagues at the local colleges that have horticulture programs:

Edmonds Community College

South Seattle College

Lake Washington Institute of Technology

And here is a link to a college in Ontario, Canada - Niagara College - that is doing something similar to what you describe.

Season All Season
Date 2008-01-03
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Keywords: Eriobotrya japonica

PAL Question:

Will loquat trees grow here in the Puget Sound, and which varieties are best?

View Answer:

In his book Trees of Seattle (2006), local author Arthur Lee Jacobson lists a small number of loquats growing in Seattle, all of them young trees. On his website, he at least mentions the potential for fruit if the winter flowers are not killed by frost. The book From Tree to Table: Growing Backyard Fruit Trees in the Pacific Maritime Climate (Barbara Edwards, Skipstone Press, 2011) says that loquat (Eriobotrya japonica) will grow well here as an ornamental tree, but it is extremely rare for it to produce fruit in USDA hardiness zones 8a and 8b (Puget Sound). (In warmer areas--zone 9 and 10--these are some of the recommended varieties: Gold Nugget; Champagne; McBeth; Big Jim.)

The website of California Rare Fruit Growers provides general information on growing loquat.

Season All Season
Date 2013-11-14
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Keywords: Pteridium aquilinum, Perennials--Care and maintenance, Ferns--Washington

PAL Question:

My question has to do with the fall/winter foliage of bracken fern (Pteridium aquilinum). A friend trimmed the bracken to the ground. Will the bracken grow back next spring? This led to other questions. Does bracken lose only its leaves in the winter or does the entire plant die off? Does it spread through its roots or spores? Any information you have would be appreciated.

View Answer:

Bracken is deciduous, that is, the fronds die to the ground in winter and then regrow from the rhizomes in the spring. If your friend cut her bracken down to the ground late in the year there would be no problem. Even if it was earlier in the year, the bracken would probably survive. According to the fern books I read, people have tried mowing to remove their bracken with no success. The books also warn that bracken is very invasive and not recommended for small gardens. It spreads by underground rhizomes, maybe by spores as well, and can take over a large space in a very short time.

It might be a good idea to take a look at some pictures either in books or online (just enter the name in Google and select Images above the search box) to make sure this is what your friend has. Any deciduous fern (and even some evergreen ferns) can be cut to the ground in fall, but generally it is better to wait until the new fronds appear in spring to cut out the old fronds of evergreen ferns.

The USDA Plants Database provides further information.

Sources consulted:
The Plantfinder's Guide to Garden Ferns (by Martin Rickard, 2000)
Ferns to Know and Grow (by F. Gordon Foster, 1984)

Season Fall
Date 2008-01-03
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Keywords: Calamagrostis, Melica, Elymus, Bromus, Festuca, Native plants--Care and maintenance, Ornamental grasses, Drought-tolerant plants

PAL Question:

I am looking for a native, drought-tolerant grass for a small garden plot in Seattle. Can you suggest a grass that is 2-3 feet tall and at most 2 feet wide.

View Answer:

Native grasses that will do well in a dry meadow setting and grow 2-3 feet tall are:

Festuca idahoensis, Idaho fescue
Bromus carinatus and Bromus marginatus, brome grasses
Elymus glaucus, wild rye grass
Melica species, onion grasses
Calamagrostis nutkaensis, Pacific reedgrass

Each of these grasses grow in very distinct shapes--I recommend that you look at them before choosing which species to plant. Fescues are popular grasses for gardens because of their fine blades and pretty seed heads. Additionally, the Elymus and Bromus will grow much more quickly than the other species.

You can perform searches on each of these species at the USDA Plants Database by typing the plant name into the Plants Name search box--
this database will give you additional information about the species and some pictures.

The Washington Native Plant Society website has a list of native plant vendors.

Season All Season
Date 2008-01-03
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Keywords: Calathea, House plants

PAL Question:

How do I care for Calathea zebrina?

View Answer:

The webpage of Plant of the Week have information about Calathea zebrina (zebra plant, native to Brazil):
"For the home or greenhouse. Plants reach 3 feet in containers. Leaves emerge from basal rosettes and may reach 2 feet long by 1 foot wide. Calathea zebrina need shade and temperatures above 55 degrees, but they need good light for a good, rich leaf color...use a soil mix consisting of 2 parts peat moss to 1 part loam to 2 parts sand or perlite. Good drainage is necessary or the plant will stagnate, which is a common problem. The plants should be kept moist at all times and leaves should be misted often. Fertilize every 2 weeks during the growing season and once a month during the winter months. Repot as often as necessary to avoid root bound conditions."

Season All Season
Date 2008-01-03
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Keywords: Trachelospermum, Landscaping drain fields, Camellia

PAL Question:

Here is the situation: I have six inches between the cement wall and the septic drain field. I want a green screen between myself and the neighbors on the other side of the short cement wall. What can I grow that will give me a green screen and not invade the septic system pipes? All I can think of is some sort of climbing vine, but I am not familiar with which root systems could be a problem.

View Answer:

You have a real challenge with your situation. Most of the literature says that you should not plant any large shrub or tree within 30 feet of a septic system drain field.

Roots growing into the drain field is a serious concern. They recommend consulting an expert if you do want to plant near a drain field.

Instead, you might consider installing an attractive fence and/or using containers to grow plants in. For example, Camellias can be grown on a trellis from a container. They are evergreen, and will also flower. Another vine-like plant is star jasmine, Trachelospermum jasminoides. It is evergreen with fragrant white flowers.

Season All Season
Date 2007-04-10
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Keywords: Vitis

PAL Question:

Do you have any information on a new grape variety called Sweet Seduction? I am interested in vigor, fruit set, and ripening time.

View Answer:

Depending on the source, this is either a beautiful and productive grape or a straggly one with poorly filled clusters. It received praise from Lon Rombough, a grape expert from Oregon. The Home Orchard Society has a brief discussion about Sweet Seduction. These first two sources do not think much of this seedless grape. It is also mentioned in a list of American grapes and hybrids in the book McGee and Stuckey's Bountiful Container (Workman, 2002):
"Introduced by Oregon grape grower Bill Schulz, Sweet Seduction is an unusual variety with exceptional flavor. It produces beautiful golden yellow seedless grapes with a muscat-like taste that we usually associate with European grapes (...) Vigorous and productive, [it] bears large and attractive clusters of its seductively flavored fruit."

Anecdotal comments on the web suggest that this variety begins to bear fruit at between 2 to 3 years after planting, and may produce 10 to 15 pounds of grapes. It is hardy in Sunset zones 5 - 9 and can grow 15 to 20 feet.

Season All Season
Date 2006-03-04
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Keywords: Luzula

PAL Question:

I am looking for information on Luzula purpureosplendens, and all I can find is very general information on the genus Luzula.

View Answer:

Luzula purpureosplendens is endemic to Azores islands, which may be why there is so little information about the species. Another reason it may be hard to find information is that it has synonymous names, according to GlobalSpecies.org, and these are Luzula azorica and Luzula purpurea. If you search either of the synonyms on the web, you will get some results, many quite technical (chromosomal studies).

Season All Season
Date 2008-01-03
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Keywords: Oplopanax horridus, Perennials--Care and maintenance, Native plants--Care and maintenance

PAL Question:

My question is about Oplopanax horridus. I planted one last winter in deep shade. It has lost its leaves and appears to have gone dormant. 1) Does devil's club go dormant in the winter? 2) If not, then could it come back with watering in the winter climate or am I better to rip it out and put in another one? 3) How frequently should devil's club be watered in a normal summer and assuming good loam soil?

View Answer:

Devil's club does lose its leaves in the winter. Quoting from the source cited below, it is hardy down to at least 5 degrees F, although the young growth is likely to be cut back by spring frosts...On cool moist soils, it forms tall, impenetrable thickets...Plant in sun or part-shade.
(Source: The New Royal Horticulture Society Dictionary of Gardening, Vol.3, 1992, p. 378)

Additionally, devil's club "grows in well-drained to poorly drained soils with sandy, silty, or loamy textures," which indicates that it will appreciate regular watering that ensures moist soil in the summer.
(Source: Propagation of Pacific Northwest Native Plants, R. Rose, et al, 1998, p. 129)

Season Winter
Date 2006-03-20
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Keywords: Acer palmatum dissectum, Deer

PAL Question:

Is the Japanese 'Crimson Queen' laceleaf maple deer resistant?

View Answer:

I found Japanese maple (Acer palmatum) on a few lists of deer resistant plants. (One source is Pacific Horticulture, v. 47 (3) 1986, "Co-Existing with Deer," by Mary Lynn Cox)

None of the lists mention specific cultivars, such as your 'Crimson Queen.' But the risk of damage should be lower than other plants that deer prefer. Every article I read warned that a starving deer will eat anything, so no plant is 100% safe.

Season All Season
Date 2006-03-03
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Keywords: Packing for shipment

PAL Question:

What do I have to do to ship a plant via the United States Postal Service? How do I prepare a plant for mailing? I want to mail a one gallon plant.

View Answer:

When sending your one gallon plant, you should mark the box Fragile and Living Plant Material. You should also use the fastest shipping method you can afford, to make sure the plant reaches its destination in good condition. You might also phone your local post office to learn whether there are any other regulations concerning mailing live plants. The U.S. Postal Service provides these basic guidelines for packaging perishable plant matter. Another matter to consider is whether plant quarantine regulations apply to the plant you are shipping, and whether or not you need a permit.

FedEx has a guide has a guide entitled Packaging Guidelines for Flowers and Plants which should help you.

In terms of packing the plant, you should also ensure that the plant does not move around in its box during transport. Avent (see the source below) recommends securing the pot to the side of the box, with strapping or similar material. You may also want to protect the vegetation with breathable material--perhaps biodegradable starch-based packing peanuts?

Source: So You Want to Start a Nursery, T. Avent, 2003, pp. 75-78

Season All Season
Date 2008-01-03
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Keywords: Quirky, Plant reproduction, Solanum melongena

PAL Question:

I read on a cooking blog that it's important to be able to distinguish between male and female eggplants, because males are less seedy and therefore less bitter. Supposedly, the difference can be detected by looking at the indentation at the bottom of the vegetable. Females have long, deep, dash-shaped dents, and males have round, shallow ones. This is the first time I've ever heard of such a thing, and I'm wondering if you can confirm it.

View Answer:

There is no sex difference among eggplant fruits. The confusion may have come from the fact that eggplant flowers have male and female parts. Mary Keith, a nutrition educator with University of Florida Extension says:
"Please, don't waste any sleep over trying to remember which one is which. There are not 'male' or 'female' eggplants. They all come from the female organs of the flower, but eggplant flowers have both male and female organs. The seeds they contain will grow into plants that make flowers with both male and female parts.[...] The shape of the scar where the flower fell off doesn't tell you whether the fruit is a boy or a girl."
Keith goes on to explain the best way to select an eggplant for cooking purposes:
"The best place to start is what you can see, the skin. There should be a little bit of the stem still attached to one end. A ripe eggplant will have a smooth, bright, shiny skin. It should be firm, not hard but not soft and soggy either. Whether it is purple, green, white or striped, if the skin is dull the fruit has been picked for too long. When you press on the skin it should spring right back at you. If it's too hard to press in, then the fruit is too green and underripe. If it goes in and stays in, the fruit is too old. The texture is getting soft and it is more likely to be bitter. In general the smaller ones are usually better. Probably the best way to decide which ones to buy is to weigh them. [...] The heavier one will be the better one. Some people say they can tell by knocking on an eggplant as they do a watermelon. In this case though, you do not want to buy one that sounds hollow. These will be dry and punky inside."

Similar information comes from University of Illinois Extension:
"There is long-standing controversy about male and female eggplants, which is an inaccurate approach considering the fact that fruits are the product of sex and do not have it. However, it is folk wisdom worth some attention. Eggplants have a dimple at the blossom end. The dimple can be very round or oval in shape. The round ones seem to have more seeds and tend to be less meaty, so select the oval dimpled eggplant."

Season All Season
Date 2011-10-28
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Keywords: Vines--Care and maintenance, Hydrangea

PAL Question:

I have had a climbing hydrangea for 4 years - but it has never bloomed. It is growing but does not produce any buds. It gets full sun and is in good soil. What can I do so it will produce blossoms?

View Answer:

I looked in a few books (including Trees and Shrubs for Pacific Northwest Gardens, 1990, by Grant and Grant) about climbing Hydrangea (Hydrangea anomala ssp. petiolaris) and they all said this vine is wonderful and robust but very slow to establish. You may just have to wait a few more years.

This hydrangea prefers a cool, moist root run so be sure to irrigate it in the summer and place a good mulch (such as compost or wood chips) a few inches deep. The mulch should not touch the trunk of the vine at the top of the soil around the vine. Established trees and shrubs don't generally need feeding. Avoid using a fertilizer that is high in nitrogen, or it may add lush, green growth at the expense of flowers.

Here is additional information, from Virginia Cooperative Extension:
Excerpts: "Climbing hydrangeas only bloom on vertical stems so vines growing on the ground will not bloom. Minimal pruning is required. They bear lacecap inflorescences with an outer ring of showy white sterile florets around creamy to yellow fertile flowers in late spring. Deadheading can be done right after flowering to save energy and for aesthetics by cutting the inflorescences off above the first leaf. Branches that extend out far from the climbing surface may also be pruned back in summer after flowering to prevent the plants from being pulled from their structures by heavy winds, ice or snow."
Reasons for lack of flowers on various species of Hydrangea:

  • Improper shearing and renewal pruning on H. macrophylla and serrata cultivars
  • Frost injury to early expanding growth buds
  • Pruning more than a month after bloom time in summer
  • Excessive shade
  • Excess nitrogen fertilization

Season All Season
Date 2008-01-03
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Keywords: Vegetative propagation, Gunnera

PAL Question:

When and how do I divide my Gunnera?

View Answer:

"Divide large types before growth starts into single crowns in midspring." (Source: American Horticultural Society Plant Propagation, ed. by A. Toogood, 1999, p. 198)

"Many gunneras are huge and so are impossible to dig up and divide in the conventional sense. For propagation, cut pieces from the edge of the clump. Pot up in a large pot and in a fibrous medium and keep moist." (Source: The Complete Book of Plant Propagation, ed. by C. Heuser, 1997, p. 40)

The sources I looked at indicate that you should divide your Gunnera in April or May. Because of the size of the plant, it may be impractical to divide the rootball. You can use a spade or pitchfork to cut sections from the main clump, and then plant those divisions in pots, keeping them moist. Gunnera is a tough plant, and should take well to this kind of division, as long as there is adequate moisture.

Should you need to protect your Gunnera over the winter months, you can cut the leaves and use them like a tent to protect the crown of the plant during the coldest months.

Season Spring
Date 2006-03-03
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Keywords: Land treatment of wastewater, Landscaping drain fields, Ground cover plants, Grasses, Drought-tolerant plants

PAL Question:

I am looking for plants suitable for a septic drain field site. I have a very large north facing slope in open sun with a drain field running along the top half. I would like to plant low to no maintenance ground covers and low growing shrubs to cover this area. This is a focal point when driving up to my house so I want it to be eye catching and interesting year round.

I thought of heaths and heathers as a possibility, but I'm not sure if the root system is shallow enough. I also would like to include native ground covers such as ferns, Gaultheria shallon and any others that you might think would work, as well as ornamental grasses and perennial flowers for interest. Can you please offer a resource for planting over drain fields or a list of plants that you think would work?

View Answer:

Trees or large shrubs should be kept at least 30 feet away from your drain field. If you do plan to plant trees near a drain field, consult an expert to discuss your ideas and needs. Trees and shrubs generally have extensive root systems that seek out and grow into wet areas like drain fields. Grass is the ideal cover for drain fields. Grasses can be ornamental, mowed in a traditional lawn, or left as an unmowed meadow. You can also try groundcovers and ferns.

The key to planting over the drain field is to select shallow-rooted, low-maintenance, low-water-use plants. When tank covers are buried, keep in mind that plantings over the tank--from inlet to outlet--will have to be removed every three or four years for inspection and pumping.

Planting your drain field will be much different from other experiences you may have had landscaping. First, it is unwise to work the soil, which means no rototilling. Parts of the system may be only six inches under the surface. Adding 2 to 3 inches of topsoil should be fine, but more could be a problem. Second, the plants need to be relatively low-maintenance and low-water use. You will be best off if you select plants for your drain field that, once established, will not require routine watering.

SOURCE: WSU Cooperative Extension - Clallam County

Information can be found here.

Thurston County, Washington, has some information about landscaping a drain field, including plant suggestions, here.

Additionally, the Pacific Northwest Gardener's Book of Lists (1997, by R. & J. McNeilan) offers a number of groundcover lists for various situations, including groundcovers for dry sites, slopes, and sun and shade. The Miller Library has this book.

Season All Season
Date 2008-01-03
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Keywords: Prunus padus, Styrax, Laburnum, Davidia, Ornamental conifers, Ribes, Larix, Chamaecyparis, Picea, Tsuga, Cedrus, Fagus, Betula, Flowering trees, Pinus, Ericaceae (Heath family)

PAL Question:

Are there any lists of shrubs/small trees that are best viewed from below, such as Styrax or Halesia?

View Answer:

While there are no lists of shrubs/small trees best viewed from below, there is a list of trees with weeping habits in The Pacific Northwest Gardener's Book of Lists (Ray and Jan McNeilan, 1997). Many genera of conifers - Cedrus (cedar), Chamaecyparis (cypress), Larix (larch), Picea (spruce), Pinus (pine), and Tsuga (hemlock) - have weeping forms, often indicated by a variety name 'Pendula' or 'Pendulum'. There are weeping birches (Betula), beeches (Fagus), and cherries (Prunus), too.

You are correct about Styrax and Halesia. Additionally, I ran across a few individual species that may be of interest to you as I researched this question:
--Davidia involucrata
--Laburnum anagyroides
--flowering currants, Ribes spp.
--flowering cherry trees, particularly Prunus padus
--various plants in the Ericaceae family have bell-shaped flowers that hang on the underside of the stem.

I would add that any tree which has a naturally graceful branching pattern and/or delicately shaped foliage (such as Japanese maples) would be pleasant to view from below, as well as from other angles.

Season All Season
Date 2007-05-21
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Keywords: Hardy plants, Osmanthus

PAL Question:

Is Osmanthus fragrans hardy enough to withstand winter in Bellevue, WA?

View Answer:

Osmanthus fragrans is a borderline hardy shrub in our area. References vary in the hardiness they quote from zone 7 to zone 9 (Bellevue is zone 8). According to a gardener here at the Center for Urban Horticulture, "it takes a special spot for it to grow and thrive here in the Puget Sound area. The places where I've seen decent specimens and blooms are plants growing up against a warm wall or enclosed somehow by other plantings, buildings, or areas near pavement." If you have a very sheltered spot, for example a courtyard where you could grow it against a south-facing wall, it might be worth a try. Otherwise it seems to be very risky.

Season Winter
Date 2006-03-03
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Keywords: Perennials--Care and maintenance, Pruning

PAL Question:

What causes my chrysanthemums to do the big flop? One even came out of the ground! We have had a lot of rain lately, and it seems like a lot of plants did the big floppy, from roses to sedum, and now the mums. Is it all weather-related?

View Answer:

Yes, certainly the weather contributes to the big flop. Certain perennials just can't stand up to heavy mist and rain.

Some gardeners stake their flop-prone plants before they flop over, while others dig them up and grow things that don't flop.

You can prune perennials to help prevent flop. Typically you cut a perennial back by 1/3 a few months before it flowers. This causes the plant to branch out, producing a bushier, shorter, less floppy plant. In The Well-Tended Perennial Garden (Tracy DiSabato-Aust, 1998), the author suggests that staking be done early: ...after the first flush of growth but before full growth. The stems need to be sturdy, and flower buds should not be formed yet...[stake] without adulterating the normal habit of the plants. Follow the natural line of the stem. (p.63)

Season Winter
Date 2006-03-03
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Keywords: Insect pests--Identification, Pseudotsuga menziesii, Master gardeners

PAL Question:

I have some large second growth Douglas firs in my yard that were topped about 20 years ago. The last several years, almost all of them have developed pitch oozing down their sides from up high. What might be wrong with my trees, and what do you think I should do now?

View Answer:

Disease and pest diagnosis is impossible without actually examining the affected plant. However, based on the symptom of oozing pitch you described, these Pseudotsuga menziesii (Douglas fir) could be suffering from one (or more) of the following pests:

Fir Beetle

Pitch Moth

Twig Weevil

For a proper diagnosis you could hire an arborist. The Pacific Northwest Chapter of the International Society for Arboriculture has a directory of certified arborists.

You could also take many photos and a plant sample to a Master Gardener clinic. This is a free service run by volunteers trained by WSU faculty. Clinic locations and times can be found at this link.

Season All Season
Date 2008-01-03
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Keywords: Plant growth inhibiting substances, Ligustrum

PAL Question:

I have a Japanese privet that has turned into a 30-40 foot tree next to my patio. How can I get it to stop blooming and dropping its flower and seeds onto my patio? Is there a hormone or something that I can use to regulate plant growth, similar to what is given to olive trees to stop them from producing?

View Answer:

There is a product called Florel which is an organophosphate pesticide that has been used to regulate plant growth. The active ingredient is Ethephon which has some health concerns, as described by the Environmental Protection Agency.

Florel was described as an alternative to the toxic chemical, NAA (Naphthalene acetic acid) which has traditionally been used to thin fruit, in an article in Arboriculture, by Harris, Clark and Matheny, 2004, p. 403). However, Florel is still a toxic product and overuse can damage your plants.

Another (non-toxic!) option would be to remove the privet and plant something which will not interfere with your enjoyment of the patio.

Season All Season
Date 2008-01-03
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Keywords: Continuing education, Master gardeners

PAL Question:

I would like to find a speaker for our garden club which meets at the Phinney Neighborhood Center in northwest Seattle. We are a small general interest club. Do you have any suggestions for resources for finding people willing to talk to our club, on topics such as winter interest in the garden?

View Answer:

Here is a link to the King County Master Gardener Volunteers who speak to groups. The Arboretum Foundation also maintains a list of speakers.

Season All Season
Date 2008-01-03
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Keywords: Lawns--Planting, Turfgrasses

PAL Question:

I want to put in a wee bit of lawn, an area of 240 square feet. I have two questions: 1) what seed would you recommend for an area that is mostly dappled shade? 2) how do I prepare the area correctly?

View Answer:

Below is information from the Master Gardeners handbook on home lawns which discusses grass seed for Western Washington gardens on page 6.

What Grass Seed Grows Well in Western Washington?

To establish a lawn in western Washington, choose a combination of turftype tall fescue grasses and turftype perennial rye grasses. A mix that adds up to about 90% of these two grass seed types will grow well in either sun or light shade in western Washington. Turftype perennial ryegrass takes full sun and stands up to traffic. Turftype tall fescues are adapted to shadier locations. In combination, the mix works for a lawn in average light conditions. Mixes containing fine-leaved fescues or chewings fescues will also establish well. Fine-leaved fescues offer bright green color, and will take some shade, but do not take heavy use.

Many commonly-grown grass types from other areas of the United States will not thrive in western Washington's cool, dry summer climate. AVOID mixes with high concentrations of Kentucky blue grasses. DO NOT PLANT Zoysia, bermuda, dichondra, centipede, carpetgrass, St. Augustine, or mondograss. Buffalograss isn't suitable for western Washington, though it may thrive in eastern Washington.

The same document linked above discusses soil and site preparation (pages 2-3):

Soil Conditions for Planting a New Lawn:
Establishing a new lawn successfully depends more on the preparation of the ground before planting than on whether the lawn choice is seed or sod. Lawn failures are often caused by poor soil conditions under the roots. Many times soil surface left for planting after new construction is infertile subsoils, with rocks, lumps, and building detritus left in it. The texture may vary from sands and gravels to heavy, poorly drained clay areas. The best soil texture for a lawn is a sandy loam, containing 60%-70% sand and 30%-40% combined silt and clay.

If the soil isn't well-drained, do not try to amend a heavy clay by dumping sand into it. Adding sand doesn't work, nor does adding gypsum. Amend the soil with organic material, which will help in creating better structure. Use compost, manure, aged sawdust, ground bark, or other organic (previously living) materials. Spread 2 inches on top of the ground and work it in thoroughly 6 to 8 inches down. Getting it completely incorporated is important, because spots of organic material in clumps may decompose and cause a low spot in the finished lawn. Rake away clods and remove large rocks and litter.

Season All Season
Date 2008-01-03
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Keywords: Multipurpose shrubs, Garden design, Perennials

PAL Question:

I have an asymmetrical flower bed in front of my house. It faces southeast and the house is white, with reflection of light. I purchase plants for full sun but they tend to get fried. I am interested in finding perennials to provide interest 12 months of the year. I prefer shrubs with a variety of texture. Plants that attract butterflies would be nice, and any grasses that are known not to grow out of control. What plants do you recommend that would give me a lush, year-round garden?

View Answer:

You may want to plant a mixture of perennials and shrubs, particularly those which tolerate bright light. An excellent book full of lists of plants is Ray and Jan McNeilan's Pacific Northwest Gardener's Book of Lists (1997). This book includes lists such as Shrubs for Interest in Each Season (pp.62-64), and Herbaceous Perennials for Full Sun All Day (pp.138-139).

I think you may find many of the other lists in this book valuable as you design your flower beds.

The Great Plant Picks website has lists of many different plants that do well in Northwest gardens, including pictures and descriptions.

There are quite a few books which address the issue of providing year-round color and interest in the garden, such as Adrian Bloom's Year-Round Garden: Colour in Your Garden from January to December (Timber Press, 1998) and his Bloom's Best Perennials and Grasses : Expert Plant Choices and Dramatic Combinations for Year-Round Gardens (Timber Press, 2010). The Miller Library also has booklists on topics like Winter Gardening and Perennials which may be of use to you.

And, here is an article entitled "Create a Butterfly Garden" (S. Lamb et al., January 2002) from Oregon State University.

Visiting local gardens throughout the year and noting the plants that appear to be thriving may help, and a trip to your local nursery can give you lots of ideas and information. The Center for Urban Horticulture (scroll back for archived posts) and the Washington Park Arboretum both feature seasonal plant highlights.

Season All Season
Date 2008-01-03
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Keywords: Ocimum, Mentha, Cooking

PAL Question:

I'm writing an article for a travel magazine about locally grown culinary herbs which are used by chefs in our area. I found a reference to something called "cinnamon mint," but there doesn't seem to be any information available about this plant. In fact, I'm not sure the name is accurate. If it's not an actual mint, are there other mint varieties used in cooking?

View Answer:

I am going on a hunch, having found nothing that suggests there is a species of mint which is called cinnamon mint, that the plant in question is actually cinnamon basil. This is commonly used in cooking. I looked in Mints: A Family of Herbs and Ornamentals by Barbara Perry Lawton (Timber Press, 2002) and noticed cinnamon basil in the index. This plant's botanical name is Ocimum basilicum 'Cinnamon,' and it is described in the chapter entitled "Herbal Mints" (as opposed the what the author calls "true mints") as follows:
"Vigorous plant with a strong flavor of cinnamon combined with the typical basil taste. Terminal spikes of purple flowers rise above glossy green foliage."

Utah State University Cooperative Extension has a publication about mint which mentions several types for culinary use.

Season All Season
Date 2010-06-11
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Keywords: Plant sales, Garden tours

PAL Question:

How can I find out about local plant sales and garden tours?

View Answer:

This page on the Miller Library's website provides information about plant sales and garden tours.

Season All Season
Date 2008-01-03
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Keywords: Mulching, Compost

PAL Question:

Can you give me some good sources for information about mulching and different mulching materials?

View Answer:

Below are many links to information about mulch, including several from Pacific Northwest government agencies. Explore these sites for lots of other useful information about gardening! There are also many helpful books on the subject, such as Mulch It! by Stu Campbell (Storey Books, 2001) and the Brooklyn Botanic Garden's guide, Healthy Soils for Sustainable Gardens edited by Niall Dunne (2009).

Brooklyn Botanic Garden has an excellent introductory article by Janet Marinelli entitled "The Dirt on Mulch", published in Plants & Gardens News, Volume 22, Number 2, Summer 2007.

ABOUT MULCH, types, and uses--Cornell Cooperative Extension (NY)

King County (Washington) Solid Waste Division mulch info
Make the mulch of it!

INFORMATION FROM THE PACIFIC NORTHWEST (generally useful)
-- Saving Water Partnership (Seattle)
--King Conservation District (Washington), manure share program

COMPOSTING COUNCIL OF CANADA:
Compost.org

Season All Season
Date 2008-01-03
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Keywords: Symphytum officinale, Weed control

PAL Question:

Comfrey root has taken over my acreage at my home. I want to know how it spreads, how to kill it, naturally and chemically, by the root. I am currently using Roundup sporadically. I don't know how it got into my yard or anything. I would like to be able to kill it off and plant nice grass there in the spring.

View Answer:

Comfrey (Symphytum officinale) has a fibrous root system which is very deep and difficult to eradicate. Any bits of root left in the soil can produce new plants. While it may be tempting to take the quick path and use RoundUp to get rid of your comfrey, you may want to consider the health and environmental consequences of this product, whose active ingredient is glyphosate. Northwest Coalition for Alternatives to Pesticides has information about this chemical.

If you avoid using herbicide, you may find additional uses in the garden for the comfrey you remove by hand. Do not rototill this plant, and always wear gloves when handling it. Dig carefully and remove as much as you can of the roots, and then dispose of them. Pacific Northwest gardener and author Mary Preus writes about comfrey in The Northwest Herb Lover's Handbook (Sasquatch Books, 2000):

Comfrey can play an important role in compost making, The considerable leaf mass of a mature comfrey plant, cut several times in a season, can add plenty of high-nitrogen green material to the pile. In addition, the leaves contain calcium, phosphorus, potassium, and trace minerals drawn deep from the subsoil. Just be sure there are no ripe seeds, and that no pieces of root are attached to the base of the leaves that go into the compost pile.

The leaves can also be added to potato crops as a fertilizer. After allowing them to wilt, you can use the leaves by chopping them up and placing them in a trench with main crop potatoes. As the leaves are high in potassium, they make an excellent fertilizer. Layer to a depth of 1 to 2 inches. Comfrey can also be used on other plants that benefit from high doses of potassium, like tomatoes and runner beans. It has also been used to as a top dressing around soft fruit bushes. As the leaves break down, gently cultivate them into the planting area. There is an excellent article from Organic Gardening Magazine by Jean Nick, entitled Comfrey Power, available from the online archive.

If you have large swathes of your garden which are weedy, you can also try sheet mulch as a solution. StopWaste.org has information on how to do this. To simplify, the technique is to spread out a layer of cardboard or newspaper (at 4-6 sheets thick) and cover it with a layer of organic mulch (compost, straw, alfalfa hay--available at feed stores, woodchips, coffee grounds, etc.). Then wait 6-8 months. This is not an exact science because there are many variables, such as thickness of newspaper, type of mulch and what type of plant you're trying to kill. Perennial weeds and especially coarse grass will push through the cardboard once it starts to break down so it is critical that if and when this happens you pull the mulch back and put down more newspaper/cardboard, and then replace the mulch.

Season All Season
Date 2008-01-03
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Keywords: Phormium

PAL Question:

What is the maintenance routine for Phormium?

View Answer:

According to Sunset Western Garden Book (2007), require well-drained soil, and may be prone to crown rot if the site is poorly drained. They are susceptible to damage from cold (below 20 degrees Fahrenheit). The Plant Care Manual by Stefan Buczacki (Crown, 1993) suggests that you provide them with full sun and shelter from cold winds, especially if your plants are variegated cultivars, which are less hardy. Mulch in spring and fall, and provide a balanced fertilizer mid-spring and midsummer. In fall, wear heavy gloves and cut or pull away dead foliage. You may need to divide every 5-6 years.

Season All Season
Date 2008-01-03
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Keywords: Arctostaphylos, Native plant gardening, Mulching

PAL Question:

Is is good to mulch Arctostaphylos uva-ursi? If so, would an aged bark be best or a mulch that contains manure? How deep should the mulch be?

View Answer:

Native Plants in the Coastal Garden (by April Pettinger, 2002, p. 27), says the following about mulching Pacific Northwest native plants:
"...When an established native plant garden requires maintenance, it is usually minimal: mulching is probably the most important---and often the only---maintenance required. In any garden, mulching is arguably the most beneficial care you can give your soil and your plants. There are many advantages to using mulch. It suppresses weeds, conserves moisture by minimizing evaporation, and releases nutrients to the soil...Good mulch materials are compost, decaying leaves, well-rotted manures, sea kelp, mushroom compost, seedless hay or straw, shredded prunings, natural wood chips, grass clippings and evergreen needles and cones. Commercially available screened bark---usually referred to as bark mulch---has little to offer other than its ability to conserve water; it has no nutritional value and in fact depletes the nitrogen in the soil. When spreading mulch, don't pile it too close to stems of plants. If you are using compost as mulch, spread it about 2 to 4 inches deep. Other materials may be applied to a depth of 3 to 7 inches..."

Season All Season
Date 2006-03-20
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Keywords: Insect pests--Control, Arctostaphylos, Aphids

PAL Question:

My Arctostaphylos uva-ursi has suffered from galls caused by aphids. What approach would be best to combat the aphids and when is the best time in their life cycle to attack?

View Answer:

Kinnikinnick or Arctostaphylos uva-ursi sometimes suffers from galls caused by aphids, and is also susceptible to fungal diseases. If your plant has galls, you would see distorted, thickened, and often reddish leaves which almost don't seem leaf-like. The aphids may also secrete honeydew which can then turn blackish with mold.

Douglas Justice, University of British Columbia Botanical Garden Associate Director offers these comments on Arctostaphylos uva-ursi:

The Arctostaphylos uva-ursi cultivar 'Vancouver Jade' -- a UBC introduction and one of the most widely grown cultivars in temperate climates -- is adapted to wetter conditions than many other cultivars, as it was selected from the Pacific Northwest. Nevertheless, like all kinnikinnicks, it is not a plant for poorly drained, shaded or high traffic areas. And unfortunately, it appears to be rather more susceptible to manzanita pod gall aphid than other cultivars. Populations of that insect pest can build up during "warm winter" periods (such as we've been experiencing in Vancouver over the past several years) and disfigure plants significantly.
Source: UBC Botanical Garden Forums

Oregon State University has information about leaf gall on Arctostaphylos uva-ursi in their Plant Disease management handbook online.

The following, from Pacific Northwest Insect Management Handbook (WSU, OSU and U. of Idaho, 2005) provides more information about the aphids.

Kinnikinnick Arctostaphylos - Aphids

Manzanita leafgall aphid, Tamalia coweni:

Pest description and crop damage - Manzanita leafgall aphids are grayish or greenish in color and prefer new growth. They feed on the leaves of kinnikinnick and other manzanita species (Arctostaphylos spp.). Aphid feeding causes the leaves to thicken and form bright red galls. Older galls turn brown. Severe infestations may slow the growth of the plant.

Nongall-forming aphids also may be seen occasionally on kinnikinnick. They are greenish, soft-bodied insects that may feed on leaves or stems. Honeydew, a sweet, sticky material, may be associated with aphid feeding. It may attract ants or become covered with a growth of dark, sooty mold. Severe infestations may result in leaf and twig dieback.

Management-biological control: Syrphid fly larvae are important predators of leafgall aphids, and will feed on them inside the galls. Avoid use of broad-spectrum insecticides which kill these and other beneficial insects such as ladybird beetles and parasitic wasps.

Management-cultural control: Prune off and destroy galls where seen. Avoid frequent shearing and overfertilization, which encourages succulent new growth favored by aphids. Wash other aphid pests from plants with a strong stream of water or by hand-wiping. Avoid excessive watering, and use slow-release or organic sources of nitrogen. Control ants, which "farm" aphids and protect them from predators in order to harvest their honeydew.

Season All Season
Date 2008-01-03
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Keywords: Potted plants, Roots, Planting

PAL Question:

For how long can purchased plants remain out of the ground?

View Answer:

If the plants are in pots, they can stay out of the ground as long as needed. Keep them watered and they will be fine. But if they are bare root, then you should plant them temporarily (called heeling in) in a trench until you can get them into their proper holes. The most important thing to remember is to keep the roots moist. Keeping the plants out of the sun can help reduce stress as well. If digging a trench is impractical, then cover the roots with damp towels or burlap bags. Of course, planting sooner is better!

Season All Season
Date 2006-02-23
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Keywords: Abelia, Pruning

PAL Question:

I recently bought an Abelia 'Edward Goucher.' When I got it home, I noticed a lot of the stem tips were broken off. I figured it probably happened when the salesperson pulled it away from the other plants. I tried to be very careful when I planted it, but again, some of the tips bent and broke. Then after a rainstorm the other day, I found a couple more broken. I love the plant, but is it going to be that fragile? I planted it on the southwest side of my house. Will the stems grow more sturdy?

Also, what is the best way to prune it? I thought I read that you shouldn't just trim branches but rather take some back to the ground. So if branches keep breaking, what will happen?

View Answer:

Woody shrubs purchased in nurseries often have the damage you describe, mainly from being packed into a truck for transport from the grower. Abelias are not particularly fragile when established - the branches thicken up and get stronger with time. You are right about not trimming (shearing) branches but cutting them to the ground or to a strong main branch.

The best guide to pruning abelias that I found is in Cass Turnbull's Guide to Pruning (Cass Turnbull, 2004, Sasquatch Books). She recommends removing whole branches if they are dead or damaged. When the plant is older, she suggests removing some of the lower branches that grow along the ground, and some of the taller branches that grow straight upwards. As mentioned, prune them back to a main stem. You can remove up to a quarter of the branches at a time. Pruning is best done in the winter months; pruning an abelia during the growing season will encourage it to grow even more. (In your situation, though, you might want to do some pruning during the growing season to encourage this sort of quick growth.)

Of course, if all your branches are broken, you will have to wait a year before you can do this kind of pruning - don't cut them all off. Old, overgrown plants can be cut to the ground for renewal, but a new plant probably will not survive this.

Finally, remember that this variety grows to 5 feet. Trying to keep it smaller by shearing it will lead to growth of water sprouts, and even more pruning...Cass explains all of this very well.

Season All Season
Date 2008-01-03
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Keywords: Euphorbia pulcherrima, Poisonous plants

PAL Question:

Just how poisonous are poinsettias? My mother lives in a nursing home, and the director just confiscated nearly 200 potted plants that were donated to residents for the holidays. I think he overreacted. Do you agree?

View Answer:

I agree with you. It is a fact that poinsettias (Euphorbia pulcherrima) are in the Euphorbiaceae family, and the sap of plants in this family is irritating to the skin and eyes. However, it seems highly unlikely that people would be exposed to the sap of these plants, and it would take eating large quantities of leaves to become seriously ill. It's not a good idea to eat the leaves of most indoor plants, in any case.

There is information about the degree to which poinsettias are poisonous on the following sites:

It's possible the director of the nursing home was alarmed by a recent news story about a local woman who went to the emergency room after weeding in her garden and getting Euphorbia sap in her eye. There is a big difference between stationary houseplants which one mainly looks at without touching, and the aggressive and weedy Euphorbia species one pulls from the garden (only with gloves and goggles)!

Season Winter
Date 2014-12-13
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Keywords: Hummingbirds, Animal-plant relationships

PAL Question:

We have a dead cherry tree in front of our house. We're sad that it died since birds loved it and it bloomed starting early winter. We'd like to find someone to replace it for us and we'd like the new tree to be small to medium in size and be a draw for hummingbirds and other birds as the old cherry tree was. What tree would you recommend to replace our old cherry tree?

View Answer:

We recommend you select a certified arborist to remove the dead tree. There is a list online here where you can narrow a search to your area.

There are some evergreen, flowering shrubs which appeal to hummingbirds, such as Grevillea, which can reach 8 feet tall, depending on the variety. Arctostaphylos (Manzanita) species and Abelia grandiflora are also possibilities.

Trees which are attractive to hummingbirds (according to Welcoming Wildlife to the Garden, by Catherine Johnson and Susan McDiarmid, 2004) include Malus species (crabapple), Crataegus (hawthorn), and Sorbus sitchensis (Sitka mountain ash).

Here are some websites with more suggestions:
Backyard Wildlife Habitat
WA Dept. of Fish and Wildlife Backyard Wildlife Sanctuary
USDA National Resources Conservation Service's Backyard Conservation tips

Season All Season
Date 2008-01-10
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Keywords: Poisonous plants, Ilex

PAL Question:

Is a holly tree toxic to animals (dogs/cats)?

View Answer:

The ASPCA website on plants which are toxic to animals lists holly (Ilex spp.), as does the Humane Society website.

According to Plant Alert, A Garden Guide for Parents (by Catherine Collins; 2001), and Plants That Poison (by Ervin M. Schmutz and Lucretia Breazeale Hamilton; 1979) the red or black berries on holly are poisonous to humans as well, and can be fatal to small children if eaten in quantity.

If you believe your dog or cat has consumed holly berries, call your veterinarian for advice as soon as possible, or call the ASPCA Animal Poison Control number, 888-426-4435 (not a free service).

Season All Season
Date 2006-03-06
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Keywords: Soil amendments, Mulching, Compost

PAL Question:

Help! My clay soil is stunting the growth of my plants. I've amended the soil with compost and manure. Is there a another method of conditioning the soil that you can recommend?

View Answer:

First and most important, it appears mulching is the best organic solution for conditioning clay and heavy soils. Organic soil conditioners include compost, well-rotted animal manures, and natural fertilizers. Planting green manures such as clover, rye grass, or vetch are also effective for breaking up large clods in clay soil over time.

Sheet composting - laying compost over the entire area to be worked and using a fork (or rototiller) to work it into the soil to a depth of 2-4 inches - is cited by the resources listed below as an efficient method of soil conditioning. Both books listed below recommend repeating this process at least twice a year, in early spring and in late fall.

Secrets to Great Soil [by Elizabeth P. Stell, 1998, (pbk)] and
The Gardener's Guide to Better Soil [by Gene Logsdon, 1975, (pbk)]

The Saving Water Partnership (the City of Seattle and other government entities) has a website full of information about improving soil.

The site includes Growing Healthy Soil.

Current thinking contradicts the notion of working compost or other amendments into the soil, as explained in a March 31, 2010 Garden Professors blog post (no longer available online) by Professor Linda Chalker-Scott of Washington State University Extension Horticulture. She specifically takes issue with the "Growing Healthy Soil" information linked above. Here is an excerpt:
"Not only will extensive digging or rototilling destroy any soil structure you might have, it will also take out the roots of any desirable plants in the vicinity). [...] improper soil amendment can cause serious problems such as soil subsidence, perched water tables, and nutrient overloads. This last point is especially important to anyone living near aquatic ecosystems, since excess nutrients always end up in the water. Before you plant this year, find out what your soil needs before amending it. And remember that mulching is the natural (and sustainable) way to add organic matter to the soil."

Season All Season
Date 2006-12-08
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Keywords: Whiteflies, Insect pests--Identification, Insect pests--Control, Root weevils, Rhododendrons--Diseases and pests, Dahlia

PAL Question:

I have a line of Ward's ruby azaleas. The three weakest ones have a lot of tiny notches in the leaves. I seem to remember the notches from the root weevil as being larger than these. Are the tiny notches from something else?

I also noticed that some of my dahlias have splotched leaves and that when I disturb the leaves, white-looking insects fly off the leaves. These flies apparently have spread to tomatoes as well. Are these whitefly? Will they disappear after the winter or is there some control I should use to prevent them from taking over?

View Answer:

First you need to get an accurate diagnosis of your problems. If you are in King County, you can bring samples to a Master Gardener Clinic.

Oregon State University offers this information about root weevils and Rhododendron (which includes Azaleas). It describes using beneficial nematodes as a control.

According to Washington State University Cooperative Extension's publication, How to Identify Rhododendron and Azalea Problems (1984), root weevil damage to foliage is not usually a serious problem. You can check for weevils with a flashlight at night to confirm that they are the source of the notches you are seeing. There are some Neem oil-based products that may be helpful, but they must be used at the correct times of year. See WSU's HortSense page.

As for the dahlias and tomatoes, it is important to determine exactly what the insects are before proceeding with treatment. If they are whiteflies, you can put yellow sticky traps around the plants to trap them. University of California, Davis's Integrated Pest Management site has other recommended control methods, including reflective mulch. You may not want to use insecticidal soap:
"Insecticides have only a limited effect on whiteflies. Most kill only those whiteflies that come in direct contact with them. For particularly troublesome situations, try insecticidal soap or an insecticidal oil such as neem oil or narrow-range oil. Because these products only kill whitefly nymphs that are directly sprayed, plants must be thoroughly covered with the spray solution. Be sure to cover undersides of all infested leaves; usually these are the lowest leaves and the most difficult to reach. Use soaps when plants are not drought-stressed and when temperatures are under 80 degrees F to prevent possible damage to plants. Avoid using other pesticides to control whiteflies; not only do most of them kill natural enemies, whiteflies quickly build up resistance to them, and most are not very effective in garden situations."

Season All Season
Date 2008-01-10
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Keywords: Perennials--Care and maintenance, Vegetative propagation, Iris

PAL Question:

When is the best time to divide and transplant Irises? I have Japanese, bearded and yellow flag (I think) irises.

View Answer:

Rhizomatous irises (the kinds you have) are best divided in midsummer:

Lift rhizomatous kinds, such as bearded iris, in midsummer and cut rhizomes into sections, each with roots and a fan of leaves; replant, with tops barely covered, 6 inches apart. Flowers will be sparse the next year, but good thereafter.
(Source: American Horticultural Society Plant Propagation, ed. by A. Toogood, 1999, p. 202)

The optimum time..is six weeks after flowering. This is usually in midsummer, allowing time for the new rhizome to become established and make sufficient growth to produce fans to flower the following year. New roots that began growing immediately after flowering will then be strong enough to help anchor the new plants. Early spring is another suitable time, just as the other main period of root growth is about to start, but flowering may be forfeited, and if flowers are produced the stems will almost certainly need staking. Bearded iris cultivars are tough, and if the rhizome is large they can survive out of soil for many weeks. This is not an ideal situation, but it makes transport of the plants easy.
(Source: The Gardener's Guide to Growing Irises, by G. Stebbings, 1997, p. 93)

Good instructions can be found in these articles:
Digging, Dividing, and Replanting Bearded Irises
Garden Experiences: Dividing Bearded Iris

Season Summer
Date 2008-01-10
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Keywords: Plant care, Hydrangea

PAL Question:

I am attempting to find detailed plant information on a variety of hydrangea called Hydrangea macrophylla 'Miss Belgium', and can find very little in my plant books and online. Do you have any suggestions? Some of the details I am looking for are flower shape and size, plant habit, height & spread, and foliage details.

View Answer:

I found some information about Hydrangea macrophylla 'Miss Belgium' in Glyn Church's book, Hydrangeas (Cassell, 1999):

An excellent pink in alkaline soil or in containers. The plant is ideally suited to pot and tub culture as it stays small and compact (3 ft.) and the rounded heads tend to be tiny, keeping the flowers in proportion to the bush. Its free-flowering habit and healthy nature are its good qualities. It is not the best plant for acid soils as the flowers will be a strident purple-blue.

There is a photograph of 'Miss Belgium' in Corinne Mallet's Hydrangeas: Species and Cultivars (vol .1).

Forest Farm Nursery website sells this variety, described as follows: "This delightful, compact shrub will fit the smaller garden to a 'T' and provide it with a long mid-season of rosy-crimson flowers. PSh/Med(not dry) acid:blue, alkaline:pink."

Season All Season
Date 2008-01-10
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Keywords: Malus domestica

PAL Question:

I would like to find a site that has a list of tip-bearing apple varieties. It does not have to be comprehensive. Many sites talk about them and mention only a couple.

View Answer:

A search of the North American Fruit Explorers discussion group refers to a list from the USDA Agricultural Information Service which has since been removed from their website. I found an extensive list of tip-bearing and partial tip-bearing apples from Royal Oak Farm Orchard. The list was prepared by Ted Swensen of the Home Orchard Society.

According to Michael Phillips, author of "The Apple Grower" (Chelsea Green, 2005), most apples are spur-bearing or a combination of spur- and tip-bearing; only about 1% of all varieties are solely tip-bearers (such as Cortland and Russet).

Season All Season
Date 2012-03-03
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Keywords: Lavatera, Shrubs--Care and maintenance

PAL Question:

When and how do I prune my lavatera tree? We used to think this plant was a bush!

View Answer:

Lavatera does tend to grow vigorously, and can get quite woody. You can cut a third off the top of each stem in late autumn, and then in mid-spring finish your pruning by cutting all the previous year's growth to about 6 inches from the ground. Hard pruning will encourage flowering, and keep the plant more compact. New shoots may be slow to appear (may not happen until early summer).

In my experience, a small start of Lavatera turned into an 8 foot tree in one year, and because it was in a spot where a tree was not desirable, I took a cutting, then dug up the plant, and started afresh--but this may be an extreme solution to the problem!

Season All Season
Date 2006-02-11
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Keywords: Symphyotrichum, Perennials--Care and maintenance

PAL Question:

Can tall asters be sheared or lopped off, early in the growing season to control height and make them bushier? I have Aster novae-angliae 'Wild Romance'. I love the color and bloom-time, but would like them shorter.

View Answer:

Yes, asters (now renamed Symphyotrichum) can be pruned. This is sometimes referred to in England as "the Chelsea chop," and it is a technique that may be used for a number of different perennials, as this article by Bunny Guinness in the Telegraph describes. An excerpt appears here:

"Plants now commonly manicured by their snip happy owners are Campanula lactiflora, sedums, rudbeckias, echinaceas, asters and heleniums. These have their shoots chopped back by around a third in late May/June. The basic rule is that perennials which only flower once should not be chopped or you will lose the flowers; varieties such as peonies, irises and aquilegias."

Here is similar information previously available from the Colorado State University Cooperative Extension website:

"...control the height and shape of an aster by pruning. Gardeners can pinch asters like mums, regularly removing little bits of new growth until the first of July. However, an easier approach is to cut the aster back by one half in mid-June. At this time, the aster can be shaped. Outer stems can be cut lower than inner ones to produce a nice mounded plant. This shaping tends to encourage bloom near the base of the aster and discourage ugly brown stems. Although this pruning may sound extreme, it tends to delay flowering by only a few days and produces a much prettier plant."

Season Summer
Date 2008-01-10
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Keywords: Brassicaceae (Mustard/Cress family), Vegetables, Vegetables--Diseases and pests

PAL Question:

We have a couple of beautiful heads of cauliflower and a nice set of broccoli. The cauliflower looked nice until we cut through it to find lots of little bugs, turning some of the flower inside dark. We have a few aphids on our mustard greens, but the cauli bugs do not look like aphids.

Is it possible to grow ANY Cruciferae up here without infestations? I have NEVER been able to grow ANY type without some kind of bugs. At least the aphids wait until the bok choy flowers before they infest....and our yard has lots of ladybugs! Is there any hope?

View Answer:

We recommend that you start your seeds indoors to reduce the threat of insect infestation. Once the plants have begun to establish themselves, you can move them outdoors.

These books have great information about growing vegetables in the Pacific Northwest:

Growing Vegetables West of the Cascades: The Complete Guide to OrganicGgardening (by Steve Solomon, Sasquatch Books, 2007)
Sunset Western Garden Book of Edibles (Sunset, 2010)
Winter Gardening in the Maritime Northwest(by Binda Colebrook).

Colebrook explains that crucifers are "susceptible to attack by clubroot, cabbage loopers, imported cabbageworms, cabbage maggots, and gray aphids." Sunset recommends that to prevent pests, "plant in a different site each year. Row covers will protect plants from aphids, cabbage loopers, imported cabbage-worms, and cabbage root maggots. Collars made from paper cups or metal cans (with ends removed) deter cutworms, which chew off seedlings at the base."

Season All Season
Date 2008-01-10
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Keywords: Plant diseases--Control, Fungal diseases of plants, Paeonia, Plant diseases--Diagnosis

PAL Question:

I planted some peony bulbs last year and they grew nicely until they reached about 10 inches high. One was in the ground, and the other is planted in a medium sized pot outside. The one in the ground is now dead, and the other one is not looking good. It gets dark spots on the leaves, and then the leaves die. Can you help?

View Answer:

Without additional details, it is difficult to say what may be wrong with your peonies. The Penn State Extension has information on different diseases that can affect peony plants. What you describe sounds somewhat like peony leaf blotch or measles, as shown in Iowa State University's Plant Pathology webpage on peony diseases. Here is an excerpt:
"Peony leaf blotch is also known as measles or stem spot. Warm, humid weather provides optimal conditions for infection by the causal fungus, Cladosporium paeoniae.
The leaf spots are glossy and purplish-brown on the upper sides of leaves. On the lower sides, spots are chestnut-brown. Infection is generally more pronounced at the margins of outer leaves. Leaves may become slightly distorted as they continue growing.
Fungal infections on young stems first appear as elongated, reddish-brown streaks. As plant growth continues, infected tissue near the crown may darken and become depressed. Stems on the upper portion of the plant may show individual, raised spots. To manage peony leaf blotch, cut the stems at ground level in the fall or early spring. Rake the area before new shoots appear. Fungicides are available to help control the disease, but must be used in combination with other management practices. Also, providing good air circulation and avoiding wetting the leaves when watering can help reduce disease severity."

There are other possibilities, including peony blight, also known as Botrytis blight. The Royal Horticultural Society discusses this problem:
"Peonies collapse at soil level and the stem bases are covered in grey mould. In a severe attack the leaves are also affected and the plant may be killed or so badly weakened it fails to sprout again next spring. Infections also occur frequently behind the flower buds just before they open.
This is a disease that affects both herbaceous and tree peonies. It is caused by a fungus (Botrytis paeoniae) related to grey mould (Botrytis cinerea), which may also attack peonies in a similar way.
Wilt is encouraged by high humidity which builds up around dense clumps of peonies. Increase the circulation of air by thinning out overcrowded shoots. Also avoid over-feeding, especially with nitrogen-rich fertilisers, which encourages lush, disease-prone growth.
Cut out all infected stems well below soil level, as soon as you notice them. Don't put infected material in the compost bin but burn it or put it in the dustbin, preferably in a sealed bag. If whole plants are badly affected lift and destroy them in their entirety along with the soil surrounding the roots. This total destruction is essential as the fungus can produce black resting bodies (sclerotia), which survive for long periods in the soil ready to re-infect new peonies.
There are no fungicides available to amateur gardeners at present."

I recommend taking plant samples to your local county extension agent for diagnosis.

Season All Season
Date 2008-01-10
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Keywords: Plant diseases--Control, Fungicides, Powdery mildew diseases, Integrated pest management, Dahlia

PAL Question:

What can I do about powdery mildew on my dahlias? Should I throw the bulbs away, or does it only contaminate the plant above the ground? I have heard both too much water and not enough water cause this problem. Is either true?

View Answer:

The main thing you will need to do is destroy all the foliage affected by the mildew. The mildew can survive the winter on infected foliage, and then spread to new foliage.

Powdery mildew thrives where plants are crowded and there isn't enough air circulation, so give your plants space, a sunny site, and try watering in the morning, and watering from beneath the plants (not over the leaves) so they are able to dry off during the course of the day. As you indicated, too little water can also be a problem.

Here are two websites with additional information:
Univ. of California IPM Online Guide
OSU Extension Plant Disease Control

I did not come across any information specifically saying that powdery mildew will affect bulbs or tubers. I spoke to an experienced dahlia and begonia grower here who said that it should be all right to store and replant your tubers, as long as you thoroughly get rid of all the diseased foliage aboveground.

Some sources (such as The Organic Gardener's Handbook of Natural Insect and Disease Control, edited by Barbara Ellis, Rodale Press, 1996) suggest that a baking soda spray (1 tsp. per 1 quart of warm water, with a bit of dish soap) is protective or preventive, but Washington State University Extension professor Linda Chalker Scott disputes the efficacy of this method. She says that other methods work better:
"Other treatments have been more successful in powdery mildew control, including horticultural oils, potassium bicarbonate, potassium phosphate, sulfur, milk, and even water sprays. Probably the most field success has been found in combining SBC [sodium bicarbonate] with horticultural oils, including mineral and vegetable oils (see the Fall 2008 MasterGardener magazine). The mixtures are so effective that they've been successful even on serious powdery mildew epidemics."

Season All Season
Date 2008-01-10
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Keywords: Weed control, Integrated pest management

PAL Question:

I have a smaller lawn, in a slightly shady area and have been having problems with dandelion and white clover. I don't mind a few weeds, but it is getting to be too many. Children and pets play on this lawn so I don't want to put anything that would be toxic to them on the lawn. What would you suggest I do?

View Answer:

Given that you are concerned for your children and pets, it makes sense to hand-weed your lawn. A little pocket knife is a great tool for doing this quickly and tidily. If you just spend a little bit of time at it a few days a week, it will go faster than you might imagine. Try to live with the clover; it is extremely difficult to eradicate, and it is great for honeybees.

Small dandelions are easier to pull out. The City of Seattle has excellent information about caring for lawns without pesticides, including hints about controlling dandelions. Look in the right-hand menu for additional links to lawn care information.

This Mother Earth News article (June 2, 2011) describes several types of dandelion weeding tools.

Season Spring
Date 2007-04-20
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Keywords: Native plants--Washington, Native plants--Care and maintenance

PAL Question:

Where can I buy plants native to the Pacific Northwest?

View Answer:

The Miller Library website has information on sources for native plants - see the section on finding northwest native plants.

Below is a list of nurseries close to Seattle:
1. MsK Rare Plant Nursery (and lots of NW natives) in Shoreline
2. Washington Native Plant Society plant sales and native plant and seed sources
3. Woods Creek Wholesale (and Retail) Nursery in Monroe, WA

And here is the Woods Creek Nursery's native plants list.

King County's Native Plant Guide has a list of sources, as does PlantNative.

Season All Season
Date 2008-01-10
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Keywords: Control of wildlife pests

PAL Question:

Wild rabbits invaded our garden area this year and ate 20 feet of bean plants and then ate all the leaves from my strawberry plants. What can I do next year to discourage the little creatures?

View Answer:

There is a helpful factsheet on rabbits from the Washington Department of Fish and Wildlife's Living with Wildlife website. Some of the recommended methods of control include exclusion fencing and barriers, noisemaking and scaring devices (if you have a dog, this will help!), and even planting plants that are mostly unappealing to rabbits. There is also information on live-trapping, but this is not ideal because "the animals typically become disoriented, which results in them getting hit by a car or eaten by a predator. If they remain in the new area, they may cause similar problems there, or transmit diseases to other animals in the area. If a place "in the wild" is perfect for rabbits, they are probably already there. It isn't fair to the animals already living there to release another competitor into their home range to the detriment of both of them."

Season All Season
Date 2006-02-11
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Keywords: Edible plants, Salix

PAL Question:

There's a type of willow used traditionally in Iran to make a fragrant beverage. In Farsi, it's called bid, and I think it's also known as musk willow. I need to know what the species is, and I wonder if it will grow in the Seattle area.

View Answer:

Most sources I consulted confirm that musk willow or bid is Salix aegyptiaca. Encyclopaedia Iranica says "bid" is a general term for the genus Salix, but does identify "musk willow" as Salix aegyptiaca. The online version of W.J. Bean's Hardy Trees and Shrubs: Temperate Woody Plants in Cultivation says the following:
"Native of S.E. Anatolia, S.E. Transcaucasia and N. Persia; introduced to the Botanic Garden at Innsbruck in 1874 by Dr Polak, doctor to the Shah of Persia, and in cultivation at Kew five years later. At one time a perfumed drink was made in Moslem lands from its male catkins, which were also sugared and eaten as a sweetmeat, and used for perfuming linen. For these it was cultivated from Egypt to Kashmir and central Asia, so the epithet aegyptiaca is not so inappropriate as it would otherwise seem to be."

Salix aegyptiaca is featured in the February 2016 issue of the Royal Horticultural Society's publication, The Garden in an article entitled "Willow the wish" by David Jewell. Since the article recommends it for gardens in England, where the climate is similar to ours here in the Pacific Northwest, it will probably thrive here in Seattle as well.

Season All Season
Date 2016-05-12
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Keywords: Continuing education, Horticultural therapy

PAL Question:

Do any colleges or universities in the Seattle area have programs on horticultural therapy?

View Answer:

At one time, Edmonds Community College offered a certificate in therapeutic horticulture but they do not any longer. You can find other programs available around the U.S. on the website of the American Horticultural Therapy Association.

The University of Washington doesn't offer a horticultural therapy program, though there may be individual courses through the department of Landscape Architecture. Professor Daniel Winterbottom specializes in "ecological urban design and the role of restorative/healing landscapes in the built environment." The Miller Library has a good selection of books and articles on the horticultural therapy, including information about making raised beds, appropriate tools, gardening for the differently abled, and the like. This booklist will give you an idea of the resources available. For information about library hours and directions, go here.

Season All Season
Date 2008-01-10
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Keywords: Crassula, Insect pests--Identification, Insect pests--Control, House plants

PAL Question:

My 100-year-old Jade plant is about 5 feet tall and recently has been producing a sap from its leaves. White and sticky. Is there anything I can do to help this? Is it normal? Or is it endangering the plant? It is in kind of a cool spot; should I move it to a warmer place? It is a succulent, right? I would also like some information about repotting if necessary.

View Answer:

The pests most likely to cause a white, sticky substance are aphids, whiteflies, scale or mealybugs. These are known to affect jade plant, or Crassula ovata, which is indeed a succulent. They won't destroy plants, but can weaken them and allow other problems to surface. If none of the pest descriptions below resemble what you are observing, you can take affected plant samples to a local county extension agent. Without knowing the specific pest, we can't suggest specific treatments. Northwest Center for Alternatives to Pesticides has general information on caring for houseplants. Note their description of mealybugs, which do produce a sticky substance:
"These insects look like little bits of cotton that are greasy or waxy. They are oval in shape, have a segmented body, and are about 1/4 inch long. You'll usually find them hidden between leaves and stems or under leaves. They move slowly. They make a sticky liquid called honeydew and also cause leaves to become distorted and spotted."

As for temperature and repotting, The New House Plant Expert (by D. Hessayon, 1991, p. 212), says that succulents like a difference between day and nighttime temperatures. They like to be kept cool in the winter, with 50-55 degrees F ideal, but as low as 40 is alright. Jade plants should only be repotted when essential. Repotting should occur in the spring; shallow pots rather than deep ones are preferable.

Extensive care information can be found on Succulent-plant.com. There is also excellent general information on indoor care of succulents and cacti from Brooklyn Botanic Garden.

Season All Season
Date 2006-12-08
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Keywords: Sustainable architecture, Irrigation water quality, Water reuse, Water conservation

PAL Question:

I need to replace my roof, and I am thinking of installing asphalt or composite shingles because they're what I can afford. I planned to capture rain water to irrigate my vegetable garden, but I'm concerned about toxicity. Is runoff from the shingled roof likely to be toxic?

View Answer:

I would not recommend using reclaimed rainwater from an asphalt shingle roof for any edible crop. Asphalt is petroleum-based. The runoff might be acceptable for ornamental plants, but the fact that asphalt or composite shingles tend to shed tiny particles means that those particles would be introduced to the soil around your crops.

An article from North Carolina State University Extension discusses "Water Quality of Rooftop Runoff." It doesn't specifically mention asphalt, but I don't think it would be wise to use the reclaimed water on food crops.

Green Living Journal has an article about roofing materials,and discusses asphalt shingles as well as alternatives.

The National Gardening Association site has a report that describes rainwater harvesting.
Excerpt:
"Water from the rain barrel is, of course, not potable, but some experts also raise concern about possible contaminants from rooftops that can make the water unsuitable for edible gardens. According to an article in Landscape Architecture magazine, asphalt shingles and other porous or rough roofing materials can hold particulates such as bird droppings and other debris, as well as heavy metals from the air, which then wash into the rain barrel. Wood shingles that are chemically treated to resist rot and algae can leach the chemicals into the rainwater running off the roof. Zinc strips that prevent moss build-up can also be problematic. Some large-scale rainwater collection systems are even designed to allow for the first flush of water off the roof -- which carries the majority of the questionable substances -- to be diverted.
"Other people dispute these risks and say washing your garden produce is all that's needed. It's a judgment call. I tend to research things to death so I think it would be interesting to have some of my rooftop runoff tested at the health department."

There is a very detailed and technical document entitled "Roofing Materials Assessment" from Washington State Department of Ecology (2013-2014 study results) if you wish to pursue the topic further.

If installing slate, clay tiles, untreated wood shingles, or a green roof is prohibitively expensive, the best solution might be to landscape the garden in such a way that you can reclaim runoff from the roof for non-edible plants.

Season All Season
Date 2010-01-08
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Keywords: Euonymus, Osmanthus, Ilex, Hedges

PAL Question:

Can you all give me some recommendations for plants that will form a tight hedge? I want a fast growing plant that does not get more than 2-3 feet tall and 2-3 feet wide. I do not want boxwood. Evergreen with glossy leaves is preferable; flowers do not matter to me.

View Answer:

I collected some information from websites and a couple of books for you. I am making one other plant suggestion, and it is the last item.

Euonymus japonicus 'Microphyllus'
Text
Images

Ilex crenata 'Northern Beauty' is described on the website of Great Plant Picks

Ilex glabra 'Shamrock'
See Missouri Botanical Garden for information and an image.

Osmanthus delavayi
This can be grown as a dense hedge. It can reach about 8 feet, but takes pruning well. Evergreen and attractive all year. Small, oval, tooth-edged leaves. Fragrant tiny white flowers in spring. Here in Seattle it can take the full sun but partial shade is okay too.

See the following website for both information and an image. Great Plant Picks is a local organization with information about plants that do particularly well in the Pacific Northwest.

Season All Season
Date 2006-12-08
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Keywords: Plant nutrients, Citrus limon, Potted plants, Water requirements, Fruit--Care and maintenance

PAL Question:

I purchased a small Meyer lemon plant from a nursery in Florence, OR, and it grew, and blossomed very well, and even produced many tiny lemons - all of which have now, at this point, dropped off. The leaves are yellowing, too. It is in a good size container, in full sun. The container sits in a large saucer which does fill with rainwater. This I empty, but the plant remains wet. New blooms are coming on some of the branches, old blooms are shrivelling. No more lemons coming as yet.

My question is, why did the tiny lemons drop off? And, should the plant get overly wet? My nursery person has no information. I would appreciate any information you have.

View Answer:

The following information comes from Citrus (by Lance Walheim, Ironwood Press, 1996).

It sounds as if your container has good drainage, but maybe the plant is getting too much rainwater. That might be causing the leaves to turn yellow. Another cause could be a nitrogen deficiency, which would be most visible in older leaves, which would yellow from the tip to the base.

As far as the plant's water needs, it will need water when the top two to three inches of soil become dry. Frequent watering (or excess rainwater) can leach nutrients from the soil, so the plant will need to be fertilized regularly -- once or twice a month using a liquid, high-nitrogen fertilizer that includes the micronutrients zinc, iron, and manganese.

The small lemons which drop off may not be anything to worry about, as fruit drop occurs normally as the tree varies its fruit load with its carrying capacity. Pea-sized fruit usually drop about one month after bloom. A more noticeable drop occurs in late spring to early summer, when golfball-sized fruit may drop. Other reasons for fruit drop could be conditions which limit tree growth, such as excess heat, lack of soil moisture (not relevant in your case), and fluctuating weather conditions. It is also possible that the fruit drop is due to lack of nitrogen.

Season All Season
Date 2006-03-06
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Keywords: Nurseries

PAL Question:

Is there a print or online resource for locating plants (places where they are sold)?

View Answer:

You can search the Andersen Horticultural Library's Plant Information Online. But be aware that they only include a selection of nurseries (those who post their inventory online). Most local nurseries are not included, as their inventory changes too frequently. You can also search using your favorite search engine for the name of the plant you are seeking plus the word nursery. This will not give you any clues, however, as to the reputation of the nurseries which show up in your search results. The website of Dave's Garden does have a forum of nursery reviews (called Garden Watchdog) you can consult.

Season All Season
Date 2007-09-21
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Keywords: Acer palmatum, Tree planting, Transplanting

PAL Question:

I would like to transplant a Japanese maple, probably 5 years old and about 8 feet tall. Can I do it in late October/November safely in St. Louis? And what is the best method?

View Answer:

Japanese maples are best transplanted when they are dormant---usually late fall through early spring if the ground does not freeze in your area.

The following information comes from Japanese Maples (by J.D. Vertrees, 2001, pp.61-62). This book also contains good information about mulching and general care:

When moving a plant to a different location within a garden, the plant must be dug with an earthen ball intact around the roots. If the plant is of any size or age, this root protection is important. It is also desirable that the planting hole be prepared in advance, ready to receive the plant with its root ball, as soon as it is dug up. Having the new planting hole ready minimizes the risk of the fine feeding roots drying out. For this reason it is imperative that, whatever method, material, or timing is used when planting a Japanese maple, the roots are not exposed to air or direct sunlight for any length of time. Such care will help prevent them from becoming desiccated, which would cause too much transplant shock and possible loss of the tree.

The planting hole should be dug slightly larger than the root mass of the plant. To enable the root system to establish itself quickly, it helps to mix with the soil organic compost, such as composted conifer bark mulch, rhododendron or azalea planting mix, or rose compost. In tight , heavy clay soils the compost helps condition the soil, while in light, sandy soils the compost assists in water retention. Sawdust or wood chippings should never be used as, during their breakdown, they use up the available soil nitrogen and render it unavailable to the newly planted tree.

The planting hole should be deep enough so that the root collar of the plant, the ground line at which the young plant was grown, is level with the ground surface. The exception to this rule applies to tight, heavy soils, like clay, where success will be greater if the hole is rather shallow so that the root system is partly above the ground level. When filling in the hole, the soil should then be mounded up to the root collar to protect the roots from drying out. If deep holes are dug in heavy soil, it is like planting the tree in a large iron kettle with no drainage. Surely the plant will soon drown and die.

Whatever the soil conditions, the tree should never be planted deeper than the root collar. After the first season or two, the plant will find the level of root activity at which it can exist in particular soil conditions. I have observed maples growing in some surprisingly dry, shallow, and exposed conditions.

Season All Season
Date 2006-11-14
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Keywords: Trees--Diseases and pests--Washington, Pinus, Master gardeners

PAL Question:

Recently we noticed that one of our evergreen trees has a lot of needles that are turning yellowish brown and dropping off. I would say about 25% of the needles are affected, some in the middle of the branches, some at the ends. The needles are about 3 - 1/2 inches long and are in bunches of five - I think it is a pine.

Is this normal for that type of tree? Or is it more likely the tree is stressed for some reason and we need to deal with it?

View Answer:

This will be a lengthy answer and I will assume you live in the Pacific Northwest---the following information will not apply to other areas.

In order to get an accurate diagnosis you will need to take a sample of your plant (including both healthy and affected parts if possible) to a Master Gardener clinic.

Meanwhile, to learn about diseases common to pines in the Pacific Northwest, go to the Pacific Northwest Plant Disease Management Handbook and search using the term pine.
There are several possibilities with good photos. Remedies are included with each disease.

Insect information is more difficult to get, so following are the most likely-sounding pests:

1. Pine (Pinus) - Black pineleaf scale (Nuculaspis californica)

Pest description and crop damage
Mature scales are almost circular, 1/16 inch in diameter, and yellowish brown to black. Young hatch in spring and summer. Scale feeding is restricted to the needles and results in their becoming splotched with yellow patches. Heavy infestations cause premature needle drop and may result in death of the tree. Affected trees often display a thin crown, yellow or reddish coloration, and a shortening of the needles. This insect attacks various species of pine, ponderosa most commonly, as well as Douglas-fir and hemlock.

Biology and life history
This scale overwinters as an immature. The crawlers start to disperse to fresh foliage in spring. There may be one to three generations per year.

Management-cultural control
Trees under stress tend to be particularly susceptible to attack, as are trees growing in dusty conditions. Avoid creating these types of conditions.

Management-chemical control (home)
Dormant season:
Apply with enough water to cover the entire tree thoroughly.
1. horticultural oil. Apply during delayed-dormant period.
Growing season:
insecticidal soap

2. Pine (Pinus) - Eriophyid mites (Trisetacus spp.)

Pest description and crop damage
Eriophyid mites are tiny, wormlike, whitish or tan mites which feed under bud scales or in the needle sheaths, often between the needle bases. Symptoms of eriophyid mite infestations include yellowing, distortion, and stunting of new needles, and development of numerous buds where a bud has been infested (rosetting). Severe infestations may kill needles and cause needle drop, leaving naked branch tips. Rosettes may develop into witches' broom growths. Two-needle pines, particularly lodgepole or shore pine, are affected.

Management-cultural control
Prune out heavily infested growths.

3. Pine (Pinus) - European pine shoot moth (Rhyacionia buoliana)

Pest description and crop damage
Adult moths are reddish-orange with silver markings on the wings. The mature larvae are about 5/8 inch long and reddish-brown with black heads. The larvae of the European pine shoot moth feed on tips of branches, boring first into needles or bud bases, then into the shoots. Infested tips are covered with pitch-covered webbing, often develop a characteristic "shepherd's crook" shape, and may die back. Infested needles are yellowed near the twig tips and eventually turn brown and die. All pines are susceptible, especially two- and three-needle species.

Biology and life history
The insect overwinters as larvae in the mined buds, covered with resin-coated webs. The adult moth lays eggs on new shoots near leaf bases in the late spring. The larvae hatch and bore into the needles, which turn brown by summer. By midsummer, they are mining in the buds and cease feeding by August. There is one generation per year.

Sampling and thresholds: Check for yellowed leaves at shoot tips in midsummer.

Management-cultural control
Prune and destroy infested tips in spring, before adults emerge. Be sure to prune far enough down the branch to remove the insects.

Management-chemical control (home)
1. azadirachtin (neem extract)

Season All Season
Date 2008-01-10
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Keywords: Abies, Plant diseases--Diagnosis, Trees--Diseases and pests

PAL Question:

Can I attempt to diagnose a diseased tree online? We're getting more brown spots on our grand fir and I would like to try to figure out what is wrong.

View Answer:

You can attempt it, but you will not know for certain based solely on a comparison of symptoms. You can certainly get an idea of what the potential problems could be. Try the Pacific Northwest Disease Management Handbook online---it has excellent photos. Search for fir.

There are several possibilities with brown spots as symptoms, especially:
*needle casts (there are 3 kinds)
*rust
*web blight
*current season needle necrosis
*shoot blight
*Grovesillea canker
*interior needle blight

The best way to diagnose a problem is to bring photos of the affected tree along with samples (if you can reach them) to your local county extension agent or Master Gardener diagnostic clinic.

Season All Season
Date 2008-01-10
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Keywords: Tree protection, Arbutus menziesii

PAL Question:

Are madrona trees protected within the Seattle city limits?

View Answer:

The City of Seattle, together with Plant Amnesty, maintains a Heritage Tree Program to protect notable specimens (notable for size, form, rarity, historical import), and there is also information from the city about tree protection regulations in Seattle. Madrona, a native tree, is designated as sometimes being considered exceptional (i.e., deserving protection) Click on Tree Protection Regulations (Seattle Municipal Code, Ch.25.11) in the right hand menu. Click on Director's Rule 6-2001 for a specific mention of madrones (Arctostaphylos menziesii: exceptional trees, p.4). Here is an excerpt:
"Healthy young specimens of Madronas on construction sites are more worth saving than old, large ones. As many specimens as possible in very good condition, regardless of size, should be preserved on construction sites, but they should not be watered or they will be more likely to decline and die. Large specimens of average or poor health may have a short lifespan because of damage during construction and as a result of post-construction practices such as irrigation are harmful to this species."

Season All Season
Date 2008-01-10
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Keywords: Berberis, Vaccinium ovatum, Polystichum munitum, Amelanchier, Acer circinatum, Soil stabilization, Soil erosion, Slopes (Soil mechanics), Corylus, Alnus, Philadelphus lewisii

PAL Question:

Can I plant groundcovers, shrubs, and trees to stabilize a steep slope?

View Answer:

There are several resources which will help you in selecting plants to prevent erosion and mudslides on your slope.

Please note that these articles are merely suggestions and should not be construed as advice. We are librarians, not engineers!

None of our standard books on trees mentions the soil binding quality of tree roots. However, the Miller Library does have very good technical books and articles on slope stabilization. (For example, Slope Stabilization and Erosion Control: A Bioengineering Approach, edited by R.P.C. Morgan and R.J. Rickson, 1995.)

I do want to note one thing that many articles mention: no amount of established vegetation will hold a steep slope if other forces are present that would contribute to a landslide.

The Department of Ecology website has a list of appropriate plants.

Additionally, there are a number of books with information on the subject. Vegetative Contribution to Slope Stability at Magnolia Park (by Kathy Parker, 1996) recommends Oregon grape (Mahonia), which she suggests for gentle slopes.

Other smaller plants she lists are:
Polystichum munitum (native sword fern)
Vaccinium ovatum (evergreen huckleberry)
Symphoricarpos albus (snowberry)

Larger shrubs in her list:
Alnus rubra (red alder)
Philadelphus lewisii (mock orange)
Sambucus racemosa (red elderberry)

Small trees:
Acer circinatum (vine maple)
Amelanchier alnifolia (serviceberry)
Corylus cornuta (hazelnut)

For steeper slopes, Parker says that they may not be good candidates for vegetative rehabilitation unless you put in some kind of structure. She says that Jute mats can be used in conjunction with native seed, mulch, and shrubs, if carefully anchored. She also mentions a Weyerhaeuser product called Soil Guard.

Steep Slope Stabilization Using Woody Vegetation (by Leslie Hennelly, 1994) has a plant list, as well as a chart which indicates plants used to control erosion, the degree of the slopes, and the rate of success in resisting erosion.

Two titles which focus more on the garden design aspect of planting on a slope are Hillside Gardening : Evaluating the Site, Designing Views, Planting Slopes (by William Lake Douglas, 1987) and Hillside Landscaping (by Susan Lang and the editors of Sunset Books, 2002).

Season All Season
Date 2008-01-10
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Keywords: Plant care, Leycesteria

PAL Question:

I am trying to find the proper soil pH for growing Leycesteria 'Red Shuttle'. I am hoping to plant it in partial shade next to rhododendrons (acidic soil). How will it do?

View Answer:

Leycesteria 'Red Shuttle' is the formosa species and should do well in any fertile soil, provided it is not highly alkaline (according to The Plant Care Manual by Stefan Buczacki (Crown Publishers, 1993).

Plants That Merit Attention, Vol. 2, Shrubs , (by the Garden Club of America, 1984, p. 172) states:

Needs sun for best bract and fruit color; prefers rich, moist loam; tolerates wind, drought, and air pollution...A handsome woodland shrub best in natural setting or shrub border. Needs sun for best flower and fruit color. May be pruned in spring. Partial dieback in winter not unusual; shrub rejuvenates the following growing season, often growing back successfully from roots....

Trees and Shrubs for Pacific Northwest Gardens (by J. Grant, 1990, p. 239) states:

...This shrub is easily grown in any good garden soil in full sun but prefers a rich, moist loam. It may achieve a height of as much as 15 ft. in a sheltered position. The rootstock is perfectly hardy, but the top is occasionally cut to the ground in exceptionally severe winters. If pruned almost to the ground every year, which is one method of treatment, it will send up lusty 6-ft. shoots and flower freely during the latter part of the summer....

Season All Season
Date 2006-03-04
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Keywords: Mealybugs, Scale insects, Insecticidal soap, Crassula, Insect pests--Control, House plants

PAL Question:

I have been nursing a Jade plant cutting that dropped off an overwatered and rotting larger plant. It has been thriving in my windowsill for 6 months or so, and has grown a lot already.

In the last week or so, I have noticed a strange white speckling on the upper surface of almost all of its leaves. Upon close inspection, it does not look like insects; it looks sort of like a detergent residue, and if I scrape my nail against the surface of the leaf, a lot of it will come off, albeit with effort.

Do you know whether this is something I need to treat?

View Answer:

I wouldn't assume the spots are a problem. As the following link to North Dakota State University Extension mentions, it might be salt crystals that you are seeing:
"Those dots are salt crystals and can be wiped off with a damp cloth or just ignored because they are not causing any harm to the plant. All water (except distilled) contains some salt. When fertilizer is added to the root system, the plant takes up the nutrient salts with the water. As the water moves through the leaf pores during transpiration, the salts often are left behind on the surface."

However, if you were to use a hand lens (not just the naked eye) and discover insects, there are resources with information on identifying and treating insect problems on indoor plants.

1. http://www.succulent-plant.com/pests.html

2. Washington State University's PestSense site lists several common houseplant pests, with information about treatment.

Always test any spray on one leaf before spraying the entire plant.Wait a few days after the test spray. Some plants are more sensitive to various soaps or oils.

3. The Northwest Center for Alternatives to Pesticides also has a guide to Growing Houseplants Without Using Pesticides.

Season All Season
Date 2008-01-10
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Keywords: Pumpkin, Seed storage

PAL Question:

I have some white pumpkins and I want to save the seeds and plant them next year. What should I do?

View Answer:

There are several varieties of white pumpkins, the most common being Cucurbita maxima 'Lumina.'

Quoting from The American Horticultural Society's Plant Propagation (ed. by A. Toogood, 1999, p. 300):
Leave ripe pumpkins for at least three weeks in a sunny, airy place at about 70 F to allow the seeds to mature. When the pumpkin starts to soften, cut it in half and flick out the seeds with a knife. If needed, wash off any flesh, then dry on paper towels before storing....The seeds remain viable for 5--10 years.

And quoting from Seed to Seed (by S. Ashworth, 2002, p. 29):
Home-saved seeds will retain maximum vigor when thoroughly dried and stored in a moisture-proof container...The two greatest enemies of stored seeds are high temperature and high moisture. Seeds that are stored at fluctuating temperature and moisture levels will quickly lose their ability to germinate...

Season Fall
Date 2006-02-25
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Keywords: Climatic zones, Magnolia

PAL Question:

Will the evergreen magnolia, Michelia wilsonii, grow in Danville, CA?

View Answer:

It is suitable for your area in Danville (according to the Sunset Western Garden Book). As far as surviving the full sun in your hottest summers, you might want to check with a local nursery about that to be quite sure. The Sunset book says it needs partial shade in the hottest climates [that it grows in], and your Sunset zone appears to be 9, which suggests it has high summer temperatures. It may need to be planted where it will get partial shade.

Season All Season
Date 2006-02-27
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Keywords: Weed control, Mulching

PAL Question:

What is the best time of year to use Casoron and/or Preen for weed control on ornamental beds?

View Answer:

Both of these herbicides are registered pesticides, and the law requires that they be used in strict accordance with the directions (and only on the weeds/pests for which they are registered). It is safer for you and the environment if you manage weed problems without the use of pesticides.

You may wish to know more about these particular pesticides. Both Casoron and Preen are pre-emergents, meaning that they work to kill seedlings before they sprout. This means they will not eliminate weeds that have already broken through the soil surface and are growing above ground.

Casoron is persistent in both soil and water (i.e., it hangs around). Its active ingredient is dichlobenil. There are numerous environmental and health concerns associated with this chemical. Dichlobenil will kill any plants which are exposed to it, and will harm beneficial soil microorganisms. Below is a fact sheet about dichlobenil from Northwest Coalition for Alternatives to Pesticides.

The active ingredient in Preen is trifluralin. It is a suspected carcinogen, and is toxic to fish and aquatic life, and earthworms. Here is more information from Cornell University and Pesticide Action Network UK.

The links below provide information about alternatives to chemicals for weed control. Northwest Coalition for Alternatives to Pesticides has a page of factsheets about specific weeds and ways to manage them. Here is their page on managing weeds in garden beds.

Washington Toxics Coalition also has information on ways to handle weeds in the garden. Here is more information in a PDF file.

Before reaching for chemical weed control, it makes sense to adopt gardening practices which will help keep the weed population low. Mulch is an excellent way to control garden weeds. After you manually remove weeds from an area of your garden, apply a layer of mulch. This should suppress weed growth and help retain soil moisture. Here is what garden expert Cass Turnbull says about mulch:

"Not only does mulch retain water, smother tiny weeds and weed seeds, and make it easy to pull new weeds, it is also harder for new wind-borne weed seeds to get a foothold.

"Mulch can be spread anywhere from 1 inch to 4 inches thick. The thicker it is, the more effective and longer lasting. Spread it thick in big empty spaces. Spread it thin around the root zones of shrubs to allow for sufficient air exchange, especially around shallow-rooted plants like azaleas and rhododendrons. And never let mulch stay mounded up in the base or the "crown" of a plant. It can cause crown rot on some shrubs and can kill them, even a year or more later."

Source: The Complete Guide to Landscape Design, Renovation, and Maintenance, Betterway Publications,1991.

Season All Season
Date 2008-01-12
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Keywords: Plant litter, Plant physiology, Magnolia

PAL Question:

I have noticed that Magnolia leaves seem to decompose more slowly than other leaves...can you tell me why that might be the case?

View Answer:

There is a lot of anecdotal evidence regarding your observation. Finding information to specifically confirm it is not easy, however. But some facts about plants physiology help, especially in combination with considerations about the conditions required for decay. I referred to Introduction to Plant Physiology (William G. Hopkins, 1995) for most of the information below.

Lignin is a compound that is an integral part of the cell walls of plants. (It is the second most abundant organic compound on earth after cellulose.) Lignin fills the spaces in the cell walls of various plant tissues, providing mechanical strength to the cell wall and thus to the entire plant.

Lots of lignin in a leaf would result in a slow process of decomposition because it is difficult to degrade. That is, it is not easy for bacteria and water (necessary for decomposition) to penetrate the chemical structure of lignin.

Suberin is a waxy substance that is highly hydrophobic (repels water); its main function is to prevent water from penetrating plant tissue. Suberin is found in the outermost layer of the bark (in the dead corky tissue). The cells in this layer are dead and abundant in suberin, preventing water loss from the tissues below. Suberin can also be found in various other plant structures, including leaves, where it also prevents the movement of water.

So, the combination of a structural function of lignin and the water-repelling characteristics of suberin - in leaves, in this case - is quite helpful in explaining why magnolia leaves decay at a slower rate than other leaves.

An article about composting from University of Florida Extension mentions that magnolia leaves would need to be shredded in order to be usable in compost (or as mulch).

Season All Season
Date 2008-01-10
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Keywords: Kolkwitzia amabilis, Woody plant propagation

PAL Question:

How do I propagate Kolkwitzia amabilis?

View Answer:

There are a couple of methods of propagating Kolkwitzia amabilis. Fine Gardening says to take greenwood cuttings in late spring or early summer, or remove suckers in spring.

The American Horticultural Society's Plant Propagation, edited by Alan Toogood (DK Publishing, 1999) says to take softwood and greenwood cuttings in late spring or early summer. Kolkwitzia amabilis is known to root easily from cuttings, and the new plants should flower in three years. The cuttings should be "two internodes or about 3 inches long; avoid thick, pithy water shoots and look out for tips distorted by aphids. Root semi-ripe cuttings in a tray or directly in pots. Rooting takes 4-6 weeks."

Season All Season
Date 2010-07-14
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Keywords: Hoya bella, Potted plants, Tropical plants, House plants

PAL Question:

My Hoya bella was recently moved outside. It flowered nicely, but now the leaves are a light yellow/green and the soil surface in the pot is covered with moss. What is wrong and what can I do?

View Answer:

Here is some information I found in the book, Subtropical plants: a practical gardening guide (by Jacqueline Sparrow and Gil Hanly, 2002, p. 107), quoted below:

Hoyas do very well in pots. They need bright light, but not sun...Hoyas strike fairly easily from cuttings, taken at the warmest time of the year.

About the yellowing of the leaves...I am pretty confident that this is due to the plant getting too much water (rain, whatever source, while it was outdoors) and the soil not drying out, which also explains what happened to the top of the soil--the moss or algae growth there. I would just gently scrape off the soil surface and put a thin layer of potting soil over it. If the plant starts getting what it needs again (as it did before it was put outdoors), it will hopefully return to its former healthy self.

During its growing season, Hoya bella prefers temps between 64 and 68 degrees; during its rest season, 59 degrees is the recommended minimum temperature (so here in Seattle, right next to a window may be too cold).

University of Florida provides additional information about Hoya bella.

Season All Season
Date 2008-01-10
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Keywords: Lonicera, Poisonous plants, Berries

PAL Question:

Are the berries of wild woodbine poisonous?

View Answer:

Wild woodbine or woodbine is Lonicera periclymenum. But many species of Lonicera are found in the United States.

For photos of L. periclymenum, see the two sites below:
West Highland Flora
Paghat's Garden

North Carolina University's poisonous plant website indicates that the berries of Japanese honeysuckle (Lonicera japonica) are poisonous.

Toxic Plants of North America (G.E. Burrows and R.J. Tyrl, 2001, pp.321, 322) says that while some species of Lonicera (i.e., L. involucrata) are edible, the rest are associated with digestive tract problems in children (nausea, vomiting, diarrhea), especially the European species. In the U.S., on the other hand, records of complaints are not often associated with records of clinical signs.

Season All Season
Date 2006-12-08
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Keywords: Hedera hibernica, Hedera helix, Invasive plants--Control, Noxious weeds--Washington

PAL Question:

I am trying to write a letter about English ivy in order to get it removed from a public library. Is it a noxious weed?

View Answer:

Washington State and King County noxious weed information is updated annually. Currently, three cultivars of Hedera helix and one cultivar of Hedera hibernica are Class C Noxious Weeds in the State of Washington.

Here is the link to descriptions of these four types of English ivy.

Class C Noxious Weeds are weeds that are already widespread; removal is NOT required by law. However, individual counties can adopt removal programs as they see fit. Here is the complete list of Class C noxious weeds in Washington.

King County also has more information on a website about noxious weeds.

King County does not require control or eradication of any of the four English ivy cultivars. Although control is strongly recommended, it is not required.

Season All Season
Date 2008-01-10
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Keywords: Clerodendrum, Woody plant propagation

PAL Question:

When and how can I propagate a glorybower? There are suckers coming up at the base of the plant.

View Answer:

Regarding propagating Clerodendrum trichotomum (harlequin glorybower), the book Trees and Shrubs Hardy in the British Isles Vol. I (by W. J. Bean, 1981, p. 667) says that shrubs can be propagated by root-cuttings, or by the young suckers which frequently spring from the roots.

Since you mentioned that there were suckers (gardening term) coming up around the plant, it is most likely the species is C. trichotomum and not C. bungei (one of the others commonly grown in our climate). C. bungei, according to the same source, should be divided in the spring.

Another source, Flora, Vol. 1, (chief consultant, Sean Hogan, 2003, p. 393) says regarding Clerodendrum (genus-level information) that propagation is done by sowing seed in spring or by taking cuttings of half-hardened wood during winter or summer.

Season All Season
Date 2006-03-02
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Keywords: Germination, Propagation, Acer

PAL Question:

I am interested in the seed germination requirements of Acer triflorum and Acer griseum.

View Answer:

There is information in The Reference Manual of Woody Plant Propagation by Michael Dirr and Charles Heuser (Varsity Press,2006):

Acer triflorum seed is "doubly dormant and when fall planted will germinate the second spring and sporadically thereafter. Seed, unfortunately, is often not sound [...] Nine months warm followed by 3 months cold gave reasonable germination. If seed is received dry it may be prestratified for 6 months and then sown. Germination is less than 1% the first year but is very good the second."

The authors state that with Acer griseum, "the biggest problem is poor seed quality" (between 1 to 8% viability). Also, seed production from an individual tree varies widely from year to year. "Seeds are doubly dormant and if fall planted require 2 years, some germinating the third year and beyond. The pericarp wall is extremely tough and dormancy is caused by a physical barrier as well as internal embryo conditions." Dirr says that he has cold-stratified seed for 90 days, split the fruit wall to extract the embryos, and planted them in vermiculite with a fair amount of success. Growing this tree from cuttings is considered extremely difficult, and grafting (onto seedling Acer griseum seems to be the easiest propagation method.

Season All Season
Date 2008-01-10
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Keywords: Schisandra chinensis, Woody plant propagation, Herbs

PAL Question:

How can I propagate the Schisandra fruit vine?

View Answer:

It does not sound like the easiest plant to propagate from seed. Cuttings or layering might be less challenging. The Maine Organic Farmers and Gardeners Association has a guide to growing Schisandra, including propagation information. Here is an excerpt:
"Propagate Schisandra by seed, cuttings or layering. The seeds can be planted in prepared seedbeds 1/4-inch deep in the fall soon after they ripen or indoors in March. Dry seeds need to be soaked overnight. In Herbal Emissaries: Bringing Chinese Herbs to the West, Steven Foster and Yue Chongxi say that in China an acid scarification process is sometimes used, because the seeds have such a hard coat."

Plants for a Future's database includes propagation details for Schisandra chinensis:
"Seed: best sown in the autumn in a cold frame. Pre-soak stored seed for 12 hours in warm water and sow in a greenhouse in the spring. Germination can be slow and erratic. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in light shade in the greenhouse for their first 2 years. Plant them out into their permanent positions in early summer.
"Cuttings of half-ripe wood, 5 - 8cm with a heel, August in a frame. Overwinter in the greenhouse and plant out in late spring.
"Layering of long shoots in the autumn."

Season All Season
Date 2008-01-17
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Keywords: Vegetable varieties, Tomatoes

PAL Question:

What are the best types of tomatoes for the Pacific Northwest climate?

View Answer:

In Growing Vegetables West of the Cascades (Steve Solomon, 2000, pp.241,242), the author notes that any tomato advertised in a seed catalog as needing more than 72 days for maturity will not likely reach a ripe old (tasty) age in our region. Solomon suggests purchasing seed only from regional companies like Territorial Seed Co. or West Coast Seeds. The varieties he recommends are
1. some that ripen early in the Willamette Valley (bred by Jim Baggett) = Oregon 11, Oregon Spring, Santiam, and Gold Nugget
2. slicers = Fantastic Hybrid, Pic Red, Early Cascade, and Kootenai
3. cherry = most are prolific here, but Solomon prefer's Jim Baggett's Gold Nugget

Here is a link to an article by Chris Smith in the Seattle Post-Intelligencer (01-19-2006) that introduces some new tomatoes and other vegetables for 2006.

Seattle Tilth has an article by Kirsten DeLara (2011) called "Grow Great Tomatoes in Seattle" which includes a list of the author's favorite varieties for our area. Also check Seattle Tilth's annual list of tomatoes available at their sales, and their reports on tomato tasting results.

Mother Earth News published an article on the best Pacific Northwest varieties in February/March 2010.

Season All Season
Date 2008-01-17
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Keywords: Plant exchanges and donations, Seed exchanges

PAL Question:

How can I find out about plant exchanges? I also have some plants I want to donate.

View Answer:

There are several places you can go for this information.

The Garden Web has a page with Pacific Northwest plant exchange information.

King County has a Native Plant Salvage program through which you might be able to make some contacts or find homes for plants you want to donate.

Plant Amnesty has an Adopt-A-Plant program.

Community centers, places of worship, and public schools also appreciate plant donations; contact some in your area and see if they want what you have. People also post plants to share on Craigslist.org and Freecycle.org.

The Seattle Times published this article about plant swaps and exchanges.

Finally, various plant societies/gardening organizations have plant exchanges. Here is a link to information about such organizations:
Miller Library's Organizations List

Season All Season
Date 2006-12-08
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Keywords: Plant identification, Betula

PAL Question:

Are there any tree identification guides online? In particular, I am interested in weeping birch.

View Answer:

For several excellent images of weeping birch (Betula pendula), go to Oregon State University's landscape identification site at http://oregonstate.edu/dept/ldplants/ and click on Betula in the bright orange box.
Betula pendula is toward the bottom of the page.

Also try Virginia Tech's tree identification page.

Here are some other online tree identification guides:
http://www.oplin.org/tree/
http://www.na.fs.fed.us/spfo/pubs/silvics_manual/table_of_contents.htm
http://selectree.calpoly.edu/

Season All Season
Date 2008-01-17
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Keywords: Crocus, Flowering of plants, Narcissus

PAL Question:

Many of my crocus and daffodils (especially crocus) didn't flower this year. They don't seem to be in need of separating - none of them have been in the ground for over 3 years and I don't think I overfertilized. Otherwise they seem quite healthy. What might be the problem?

View Answer:

The most common reasons that hardy bulbs like crocus and daffodils fail to flower are these:

1. Planting location: they need to be planted in full sun.
Bulbs; a complete handbook of bulbs, corms, and tubers (by R. Genders, 1973)

2. Drainage or heat: spring flowering bulbs planted in poorly drained soil or too near a heated basement (where heat from the structure warms the soil and interferes with the bulbs' necessary cold treatment) will rot or simply fail to flower.
Daffodils for Home, Garden and Show (by D. Barnes, 1987)

3. Fertilization: high nitrogen fertilizers encourage lush green growth and discourage flowering.
Daffodils for American Gardens (by B. Heath, 1995)

Season Spring
Date 2006-03-06
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Keywords: Frost, Hardy plants, Rhododendron

PAL Question:

A friend in Illinois has sent a photo this spring of a very healthy looking rhododendron - leaf buds fully elongated and beginning to unfurl, while the green, blunt flower buds remain unopened. The flower buds don't look brown, diseased, frozen or injured, but they remain tightly closed, foliage bud growth preceding blooming. He says he has 6 plants doing the same this month. Possible reason?

View Answer:

Though we can't diagnose plant problems by phone/email, early autumn frosts can inhibit flowering and not all buds are equally affected.

"Autumn frosts: These can lead to damage...if they either occur in early autumn or immediately after a late season warm spell. Continental climates with extremes of heat and cold are more likely to suffer sudden temperature changes than those with maritime climates...A sudden temperature drop will catch a plant before it has had a chance to reach maximum hardiness and it may suffer accordingly, even if normally perfectly able to withstand such a temperature in mid-winter...Speed of ripening varies considerably...There is also a variation in the hardiness of flower buds compared to foliage and growth buds. Commonly, flower buds may be as much as 10 F. less hardy than foliage..."
(Source: The Cultivation of Rhododendrons, by P. Cox, 1993, p. 119-120)

Season Fall
Date 2008-01-17
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Keywords: Pruning shrubs, Rhododendron

PAL Question:

A friend was told that pinching out growth buds before they begin to elongate as a means of shaping young rhododendrons would only stimulate buds further down the stems that were less than 4 years old - older than that and the growth buds would no longer be viable. I cannot find any information to suggest 4 years viability of dormant buds to be true, or untrue. Can you help?

View Answer:

Though pinching encourages multiple branching lower down the stem, I find no reference to it being done at a particular age.

"This practice (pinching) is recommended for most larger rhododendrons until they reach flowering size..."
(Source: A Plantsman's Guide to Rhododendrons, by K. Cox, 1989, p. 101)

That statement indicates a younger plant, but the author then mentions several exceptions.

Here is some how-to information about pruning online:
7 Solutions to the Too-Big Rhododendron.

Season Spring
Date 2008-01-17
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Keywords: sericulture, silkworm, Morus

PAL Question:

What type of mulberry do silkworms eat, and where can I find this tree (I need leaves for feeding the silkworms)?

View Answer:

Silkworms will eat any species of Morus, though white mulberry (Morus alba) is their preferred food source. See the following information from Union County College's biology department for further details.

I understand you are looking for a tree source. I wonder if you actually plan to plant the tree, or if what you really need is access to mulberry leaves. Numerous mail order nurseries carry Morus alba, Morus alba tatarica, Morus rubra, and Morus nigra, and in fact you may find local nurseries with trees, too--it's just that they don't keep an online inventory because it changes too frequently. You can search Plant Information Online for mail order sources. I did a quick search on Morus alba, and found several nurseries that carry it.

If you simply want leaves, you may want to check Arthur Lee Jacobson's book, Trees of Seattle, which lists locations of trees in both private and public gardens. You would, of course, need to obtain permission to harvest any leaves.

This website offers information on real and artificial food sources for silkworms.

Season All Season
Date 2006-03-16
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Keywords: fastigiate trees and shrubs, Cornus kousa, Trees in cities

PAL Question:

Can you recommend some narrow or fastigiate trees for the space between our house and the house next door? The space is about 14 feet wide. Will Cornus kousa 'National' work?

View Answer:

From what the experts say, Cornus kousa grows 20-30 feet high and wide in cultivation. They can grow to twice that size in the wild.

I found this and other information that might help you in the sources below:
1. Trees and Shrubs for Pacific Northwest Gardens, by J. Grant, 1990, p. 71
2. Trees & Shrubs Hardy in the British Isles, by W.J. Bean, 1976, p. 703
3. Manual of Woody Landscape Plants, by M. Dirr, 1998, p. 260
4. North American Landscape Trees, by A. Lee Jacobson, 1996, pp. xiii, 144

The Seattle City Arborist's Office recommends the following narrow trees:
1. Magnolia grandiflora 'Little Gem' - 15 ft. high, 10 ft. wide. White flowers, evergreen.
2. Malus 'Adirondack' - 18 ft. high, 10 ft. wide. White flowers, red fruit, excellent scab resistance.
3. Malus 'Red Barron' - 18 ft. high, 8 ft. wide. Red flowers, red fruit, yellow fall color.
4. Malus 'Golden Raindrops' - 18 ft. high, 13 ft. wide. White flowers, yellow fall color, abundant yellow fruit.
5. Prunus serrulata 'Amanogawa' - 20 ft. tall, 6 ft. wide. Pale pink double flowers, bronze fall color.

Here are additional sources:

Season All Season
Date 2008-01-17
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Keywords: Soil stabilization, Soil erosion, Slopes (Soil mechanics), Tree identification, Populus

PAL Question:

When a cottonwood tree is cut down, does the stump die, or does it send out shoots that grow into more trees?

And, if a cottonwood tree located on a hillside is cut down, what is the risk of erosion?

View Answer:

As it turns out, some poplars and cottonwoods sucker from the roots and some do not. Determining what kind of cottonwood you have is the key to answering this question.

Identifying tree varieties can be tricky. The best way to get a positive ID is to take a sample to the Hyde Herbarium at the Center for Urban Horticulture (near the University of Washington). It is definitely worth a visit, as it is the only herbarium on the West Coast that serves the public.

Hours, driving directions, how to collect specimens, etc. are at http://depts.washington.edu/hydeherb.

As for your second question, here is what the Washington State Department of Ecology's Vegetation Management: A Guide for Puget Sound Bluff Property Owners has to say (p.25):
Given the importance of tree cover on potentially unstable slopes and the advisability of retaining them for erosion control purposes, a landowner should explore alternative options to tree removal or topping...[if a tree must be cut] stumps and root systems should be left undisturbed...[to reduce the risk of erosion].

The above document is available online at http://www.ecy.wa.gov/programs/sea/pubs/93-31/intro.html.

A companion website from the Washington State Dept. of Ecology contains a great list of groundcovers, shrubs and trees that will help keep your slope intact if you decide to remove the cottonwood. The website includes a Plant Selection guide.

Season All Season
Date 2008-01-17
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Keywords: Pruning trees, Trees--Care and maintenance

PAL Question:

What is the definition of topping a tree?

View Answer:

The Morton Arboretum Tree-Care Handbook calls topping "indiscriminately sawing off large branches." (1994)

According to the Washington State Department of Ecology's Vegetation Management: A Guide for Puget Sound Bluff Property Owners (May 1993, p.23), the practice of topping usually refers to cutting the upper portion of the main leader (trunk) in conifers and to the removal of all branches at a particular height in deciduous trees. Topping is not advised.

Plant Amnesty has loads of information about topping - including why it should not be done - at the following link: 5 Reasons Not to Top.

Season All Season
Date 2008-01-17
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Keywords: Lysimachia, Plant care, Growth

PAL Question:

I bought a Lysimachia punctata 'Alexander' (variegated) at a plant sale last weekend. I can't find anything about it in my books. Can you tell me more about it? How tall, invasive or not, best place to plant, anything else you think I should know.

View Answer:

I found information on the website of a local gardener, Paghat, with a detailed description of this form of loosestrife. Although it is not supposed to be as aggressive as the species (L. punctata) or as invasive as L. vulgaris (a noxious weed in King County), I recommend keeping an eye on it. Paghat says:
"'Alexander' has variegated leaves, sage-green with cream borders, and sunny yellow flowers. It purports to be a more restrained version of a flower that in the species form is notoriously invasive and often too aggressive for neighboring perennials. Even 'Alexander,' though comparatively slow growing, eventually becomes a large two-foot by two-foot clump with a big root system that can threaten nearby delicate flowers, so take care what you plant around it."

Season All Season
Date 2006-12-08
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Keywords: Helleborus, Plants in winter, Pruning

PAL Question:

I am noticing that the flower bud shoots for my hellebores (Helleborus x hybridus), are starting to push up above the soil surface. There is still a substantial stand of foliage in good condition.

My question is about pruning. I know I'll need to prune about half the leaves away (I understand that the cut should be made at the base) to give the flowers more visibility. Does it harm the plant to prune it during this cold snap? Does it harm the plant to cut ALL the old leaves off in December as the bud stalks begin to appear?

I would appreciate any guidance you can give me, such as when and how extensively to prune them.

View Answer:

According to Hellebores: a Comprehensive Guide by C. Colston Burrell and Judith Knott Tyler, "all the hybrids maintain their foliage (...) throughout all or part of the winter (...) In any case, as the flower buds begin to stir in the center of the rosettes, it's best to remove all the foliage to make way for the flowers. Nothing spoils the garden display like a tangle of flowers wrestling with winter-burned leaves. The juice is caustic and sometimes causes a rash, so take care when removing the old leaves."

In The Gardener's Guide to Growing Hellebores, Graham Rice and Elizabeth Strangman advise a more time-intensive method:
"The best approach is to cut off some leaves during the autumn and early winter when the garden is put to bed, concentrating on removing dead leaves and any showing signs of blackening (...) By Christmas time they should be thinned out sufficiently to leave a good circle. However, as our winters become windier it may be wise to remove them entirely at this stage. (...)Thin the leaves further as the flower stems emerge, then just before they are in full flower remove all the old leaves. (...) To compensate for the removal of the last of the leaves the plants deserve a good mulch." They go on to suggest compost or a mulch of leaves for this purpose. The cold snap is unlikely to harm even recently pruned hellebores, as they seem to thrive in the cold.

Season Winter
Date 2009-12-09
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Keywords: Chionanthus

PAL Question:

Which varieties of fringe tree have glossy leaves? I am especially interested in a comparison between C. virginicus and C. retusus.

View Answer:

More than one variety of fringe tree (Chionanthus) is described as having lustrous leaves. According to Michael Dirr's Dirr's Hardy Trees and Shrubs(Timber Press, 1997), Chionanthus retusus has "3- to 8-inch long, lustrous dark green leaves," while C. virginicus has "3- to 8-inch long leaves [which] vary from medium to dark green, with various degrees of gloss."

If you wish to see images, you can search Google images with the different species names. Oregon State University's online guide to Landscape Plants has good detailed images and descriptions of these two species of Chionanthus.

Season All Season
Date 2008-01-17
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Keywords: Insect pests--Control, Fuchsia

PAL Question:

My fuchsias have gall mites. Will a horticultural oil control them? I would prefer not to use a more toxic pesticide.

View Answer:

Several resources I consulted confirm what you thought about using horticultural oil to control the gall mite problem. The Organic Gardener's Handbook of Natural Insect and Disease Control (ed. by Ellis and Bradley, 1996) says to spray dormant oil or lime-sulfur on dormant plants.

University of California, Davis's Integrated Pest Management site has a page about this gall mite, recommending that gardeners "plant only resistant fuchsias and consider replacing susceptible plants. Prune or pinch off and destroy infested terminals. If damage cannot be tolerated, pruning may be followed with two applications of a miticide, applied 2 to 3 weeks apart. Soap or oil sprays provide some control, but cannot kill fuchsia gall mites enclosed in distorted plant tissue."

According to a May 2004 article from the American Fuchsia Society, "to be effective, [horticultural oil] must come in contact with every live gall mite and smother every gall mite egg. The only way oil products can be effective in killing gall mites is for you to remove the leaves." Link to this article.

Season All Season
Date 2006-12-08
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Keywords: vegetables--preservation, fruit--preservation

PAL Question:

I've never done any canning before but now that I've started growing more of my own fruit and vegetables I want to know how to do it safely! I've heard about a few different canning processes (water bath and pressure). Is one method or another best for certain types of food?

View Answer:

There is a very helpful article for canning beginners in the July/August 2012 issue of Urban Farm magazine, entitled "Oh, You Know I Can!" by Lindsay Evans. You mention the only two canning methods which the article says are approved by the U.S. Department of Agriculture as safe, water-bath and pressure canning. Their National Center for Home Food Preservation has extensive information. Here are excerpts:

Proper canning practices include:

  • carefully selecting and washing fresh food,
  • peeling some fresh foods,
  • hot packing many foods,
  • adding acids (lemon juice or vinegar) to some foods,
  • using acceptable jars and self-sealing lids,
  • processing jars in a boiling-water or pressure canner for the correct period of time.

Methods that are NOT recommended are open-kettle and steam canning, or using the oven or microwave to process filled jars.

The article has a handy list of which foods work best with water-bath canning, and which with pressure canning. Generally, high acid foods (pH level of 4.6 or less) can be processed with the water-bath method and low acid foods (pH of 4.6 or more) must be canned using pressure. High acid foods include apples, apricots and other stone fruit, berries, cherries, lemons, pears, tomatoes, pickles and sauerkraut. Low acid foods include asparagus, beets, carrots, corn, green beans, lima beans, rutabagas, and turnips.

Here is a link to more canning information from the National Center for Home Food Preservation.

Season All Season
Date 2012-06-14
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Keywords: Cornus kousa, Cornus florida, Powdery mildew diseases, Trees--Diseases and pests

PAL Question:

Where can I find information about dogwood hybrids, especially crosses between Cornus kousa and C. florida? Won't these trees be more resistant to the mildew affecting many dogwoods?

View Answer:

In addition to powdery mildew, many dogwoods can suffer with anthracnose. In his book Dirr's Hardy Trees and Shrubs (Timber Press, 1997), Michael Dirr mentions Rutgers Hybrids (which are a cross of the kousa and florida species of Cornus). These trees were developed at Rutgers University by Elwin Orton, and are resistant to dogwood anthracnose. Here is an article about these cultivars, written by Orton. This article from North Carolina State University Extension discusses powdery mildew resistance. Scroll to the second table at the end which charts cultivars and their resistance or susceptibility to powdery mildew.

Oregon State University provides information about each of the six hybrids of C. florida x C. kousa. Two of the trees on this list are resistant to powdery mildew.

Clemson University Extension offers further information about the insects and diseases affecting dogwoods.

Season All Season
Date 2008-01-17
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Keywords: Nurseries, Catalogs

PAL Question:

Where can I find a list of foreign nursery catalogs?

View Answer:

We have many foreign nursery catalogs at the Miller Library, as well as a list of what we have. Call us at 206-543-0415 or 206-897-5268 (every day but Sunday) and we can fax you the list. Or stop by and look at the catalogs. Library hours and directions to get here can be found here .

In addition, the Royal Horticultural Society has a plant finder online. Go to this link and follow the instructions. You can either search by plant or by nursery (name, region, or specialty).

The commercial website Dave's Garden has a section on mail-order gardening and nursery catalogs, including some foreign ones.

Season All Season
Date 2008-01-17
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Keywords: Acorus, Thalia, Typha latifolia, Sagittaria latifolia, Pontederia cordata, Cornus alba, Cornus stolonifera, Spiraea douglasii, Athyrium filix-femina, Lysichiton americanus, Scrophularia, Wetland plants, Carex, Native plants--Care and maintenance, Soil erosion, Iris, Deer

PAL Question:

We need some advice and we are hoping you can help. We would like to replant the banks of our fish pond and want to know what kinds of plants would hold a steep slope and be compatible with the fish and each other. We have a large deer and elk population and we get substantial amounts of rain. We like grass-type shrubs and we need a ground cover that will not take over and is evergreen.

View Answer:

From the research I have done, it seems that a pond with a sloping side is a very good idea, but if erosion is a serious issue, you may want to think about both plants and physical controls such as coconut fiber matting to stabilize the banks. The Brooklyn Botanic Garden's guide (1997), The Natural Water Garden, has a description of using coconut fiber tubes (also called biologs) laid horizontally along a bank, which can also be used as a secure planting medium for seedlings.

As far as deer-resistant plants which may work for your site, iris and spiraea appear to be unappealing to deer, so you might want to try some of the irises which prefer moist situations, such as Iris laevigata, and Iris versicolor (blue flag), as well as Spiraea douglasii (hardhack).

Other plants which may help with preventing erosion are Lysichiton americanum (skunk cabbage), Athyrium filix-femina (lady fern), Carex obnupta (sedge), and Cornus stolonifera (red osier dogwood) or C. alba (red twig dogwood).

Some grassy or reedy plants which do well as marginal (water's edge) plants include Acorus calamus 'Variegatus' (variegated sweet flag), Pontederia cordata (pickerelweed), Sagittaria latifolia (American arrowhead), and Typha latifolia (cattail). All of these are deciduous.

For evergreen plants, you could try Scrophularia auriculata 'Variegata' (water figwort), an evergreen perennial with cream-edged foliage. The flowers should be deadheaded to prevent self-seeding. Thalia dealbata (hardy canna) is evergreen, with long-stalked blue-green leaves and violet flower spikes.

Season All Season
Date 2006-03-20
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Keywords: Continuing education, Environmental education

PAL Question:

I am interested in finding a speaker in the Seattle area who can talk about environmental issues, from conservation, ecology, sustainable gardening, and so on. Can you help?

View Answer:

You can try contacting Seattle Tilth at 206-633-0451, or email them at tilth@seattletilth.org.

Plant Amnesty may be able to help you (206-783-9813), or email them at info@plantamnesty.org.

Other resources include:

King County (Washington) Master Gardeners maintain a speakers list which is updated annually. The speakers address a wide variety of gardening topics.

The Arboretum Foundation also maintains an annually updated speakers list.

Season All Season
Date 2008-01-17
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Keywords: Tulipa, Planting

PAL Question:

Will my Darwin hybrid tulips come back every year?

View Answer:

In his book Ask Ciscoe (Sasquatch Books, 2007), local garden expert Ciscoe Morris suggests planting Darwin and Empress hybrid tulips 12 inches deep (rather than the often recommended 6 inches) so that the bulbs will be less likely to divide and the squirrels less likely to dig them up.

Ann Lovejoy says much the same thing...plant tulips 10 inches deep, in a sunny spot, and in well-drained soil, and some are likely to return for several years. (See Seasonal Bulbs, 1995, p.16)

Season Fall
Date 2008-01-17
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Keywords: soil contamination, Wood preservatives, Pesticides and the environment

PAL Question:

We are thinking about putting in a retaining wall and a fence on our property, which is near a lake. Should we avoid using pressure treated wood? If so, what are some alternatives?

View Answer:

There are many reasons not to use treated wood for your fences and/or retaining walls. The chemicals most used to preserve wood---creosote (on railroad ties, among other things) and penta---were banned by the EPA in 1986 for indoor use and for many outdoor uses. The chemical used to pre-treat wood (CCA, a mixture of copper, chromium, and arsenic called chromated copper arsenate) has been shown to leach into the soil and to transfer to human skin through contact.

There are safe paints and preservatives for coating wood; there are safe types of pre-treated wood; some people use stone, cement blocks, or other materials instead of wood.

Below is lots of info about treated wood and alternatives.

Start with the page on the EPA site, which is full of information on treated wood. It includes a section on alternatives and some questions and answers about studies.

If you find this too technical, try the next two links below.
The Natural Handyman website has good information.

Washington Toxics Coalition has a page about safe and unsafe paints and wood preservatives. Lots of background information on the toxicity of treated wood is included as well.

Season All Season
Date 2006-12-08
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Keywords: Plant inspection, Plant quarantine

PAL Question:

I will be transporting plants from Oregon to Washington to sell to the public. Are there any restrictions, such as quarantines, that are important to know about?

View Answer:

You should contact the U.S. Department of Agriculture's Animal and Plant Health Inspection Service (APHIS).

The Oregon Department of Agriculture has information on plant exports, quarantines, and permits. There are also Washington State codes about the transportation of plants that can be found in Chapter 17.24 RCW, Insect Pests and Plant Diseases. You can then click on specific sections, such as 17.24.081, Prohibited acts.

Additionally, this site makes reference to the Washington Administrative Code and includes information about standards that apply to plants and pests. See Chapter 16-402 WAC, Plant Pest Infestations and Plant Labeling standards.

You can also click on the embedded links to look at the specific standards.

Season All Season
Date 2008-01-17
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Keywords: Digitalis, Cutworms

PAL Question:

I have grey-green fairly large caterpillars eating my foxgloves. They are eating them to shreds but I have hopes that they will still flower. They are leaving what looks like rodent droppings in the leaves. They are eating only the foxgloves. My question is what are they and is it okay to keep the plants or should I pull them up?

View Answer:

I strongly suspect you have Variegated (or Climbing) Cutworms. I have these nasty bugs too and can give you a long list of plants they eat. Foxgloves are their favorite. Here are some management solutions in order of most work, least toxic to less work, but more toxic:

1) hand-pick after dark (with a flashlight) starting in January and continuing through May.
2) spray Bt (Bacillus thuringiensis) (found in Caterpillar Killer). It must be reapplied after rain. Be careful where you spray it because it will also kill butterfly caterpillars.
3) general pesticides will kill cutworms and many other critters that come along, including bees and may harm birds.

Here are some links to more information:
U.C. Davis Integrated Pest Management
North Carolina Cooperative Extension

Season All Season
Date 2008-01-17
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Keywords: Plum, Aphids, Prunus

PAL Question:

My prune tree has tons of aphids in the leaves (also a lot of ladybugs to eat them but I am not sure the ladybugs will win out). Do I need to try to rid the tree of the aphids? If so how?

View Answer:

The question of whether to control aphids in your prune tree really depends on how bad the infestation is and if the tree is otherwise healthy enough to outgrow them. Often infestations like aphids are a symptom of a larger problem. The tree may be stressed out by root competition from grass or too much or not enough water, too much or not enough nitrogen. A stressed out tree is attractive to aphids, who in turn attract lady bugs. My own mature prune tree gets covered in aphids every year. The leaves get distorted, and lady bugs come in droves. Some years I get a good harvest and some years I do not. I choose not to worry about it (I have other plants to fuss over). But if you feel the need to do something, see the HortSense website from Washington State University.

Season All Season
Date 2008-01-17
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Keywords: Root weevils, Rhododendrons--Diseases and pests, Gaultheria shallon

PAL Question:

Last year I had a big problem with weevils in my salal, rhododendrons and a few other shrubs. I am not sure if they returned after putting down beneficial nematodes last fall.

View Answer:

Weevils are tough! You are on the right track with beneficial nematodes. It might take a few seasons to make a difference. Here is a link to information by entomologist Art Antonelli of Washington State University about controlling weevils, especially on Rhododendron. Here is another article from Thurston County Hazardous Waste.

Season All Season
Date 2008-01-17
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Keywords: Insect pests--Control, Integrated pest management

PAL Question:

Is it normal to have many different insect pests in one garden? Is it a sign that I am not taking care of my plants well? Everything looks fine except for one infestation after another!

View Answer:

As far as I am concerned it is perfectly normal to have all of these pests (because I also have many)! But some gardeners are more ruthless than I am. They would rip out the plants. Others would assault their garden with chemicals. I prefer the middle ground of tolerance of some damage and using low-toxic controls.

The mantra these days is RIGHT PLANT RIGHT PLACE and HEALTHY SOIL = HEALTHY PLANTS. For further information (and support) go to the Seattle Public Utilities website, which has a number of great publications on Natural Lawn and Garden Care. There are lots of links to browse.

There is also information about Natural Pest, Weed, and Disease Control.

Other good resources are Washington Toxics Coalition and Northwest Center for Alternatives to Pesticides.

Season All Season
Date 2006-12-08
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Keywords: Flowering of plants, Syringa

PAL Question:

I have a lilac shrub that is about six or seven years old and blooms every other year. This seems very odd to me. Most lilacs bloom every year. Is blooming every other year normal? It is planted in optimal conditions and looks very healthy.

View Answer:

Quoted directly from Lilacs for the Garden, by J. Bennett (2002, p. 99): "Some lilacs, especially cultivars of the common lilac (Syringa vulgaris) bloom better, or only, in alternate years. Pruning the plant soon after it does bloom may encourage flowers the next year."
University of Nebraska Extension says that "removing the seed capsules soon after flowering has been reported to alter the every-other-year flowering cycle in some lilacs. This is because less energy goes into the current year's seed production and more into the next year's flower production. Some researchers agree with this recommendation and some do not. Removing seed capsules also improves the plant's appearance."

I could not find a list of which cultivars do this. You might consult the International Lilac Society to see if a list exists.

Another resource is the Hulda Klager Lilac Gardens (in Woodland, WA about 30 minutes north of Portland).

Season Spring
Date 2008-01-17
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Keywords: Brugmansia, Poisonous plants, Quirky

PAL Question:

I know that Brugmansia has toxic and intoxicating properties. I heard a story about a railway carriage in Europe that was filled with the Brugmansia flowers. When the doors to the carriage were closed, the fragrance of the blooms caused the passengers to lose consciousness, and their valuables were stolen. Plausible, or urban legend?

View Answer:

Brugmansia, like the related solanaceous plant Datura, contains tropane alkaloids throughout the plant, including the seeds and flowers. One of these alkaloids is scopolamine. There are many tales of "Devil’s Breath," a processed form of scopolamine (as powder), or scopolamine-rich seeds being used by criminals in various parts of the world to drug their victims into unconsciousness. There is an article in The Guardian (September 2, 2015) which suggests it's unlikely that this substance would have been used to "zombify" travelers in Europe. There are, however, travel security warnings from the U.S. State Department about its use by criminals in Ecuador and Colombia.

A scientific article, "Volatile compounds emitted from flowers and leaves of Brugmansia X candida (Solanaceae)" (G.C. Kite and C. Leon, in Phytochemistry, 1995) states that volatile tropane alkaloids could not be detected in the fragrance of either flowers or leaves; the main volatile organic compounds emitted by the flowers are terpenoids, benzenoids, and indole. Those compounds can cause headaches but it seems unlikely they would act like a sedative.

The book Plant Intoxicants by Baron Ernst von Bibra (Healing Arts Press,1995) describes use of Datura seeds by criminals in India to knock out their victims. There are many traditional medicinal uses of Brugmansia among the indigenous tribes of Colombia, but the hallucinogenic effects are especially frightening. One tribe describes the pleasant scent of the flowers but warns that the plant is inhabited by an evil spirit and all who sit at the foot of the tree "will forget everything." (Source: Plants of the Gods, Richard Evans Schultes, Healing Arts Press, 2001). However I cannot find any confirmation for your colorful story of a train carriage full of drugged passengers among the Brugmansia flowers.

Season All Season
Date 2016-07-21
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Keywords: Color guides

PAL Question:

I need a reference that lists the greenscale color of leaves (or plants).

View Answer:

It would be helpful to have more information about what you are trying to do. There are charts which show different shades of green in leaves as evidence of nitrogen levels, but these are mainly used in agricultural settings, such as rice cultivation.

If you are looking for charts used in horticulture, one tool for answering questions about plant colors is the Colour Chart put out by the Royal Horticultural Society. This is a set of numbered cards, in every imaginable color, that you can hold up to a flower or leaf in order to determine the standardized color. There is an extensive set of colors in the green scale. The problem with the RHS color chart is that it is expensive. If you are able to visit the Miller Library, we have a copy of this color chart that you are able to use in the library.

The Azalea Society of America has a page of information on color systems which includes the RHS Colour Chart, the Universal Color Language, Munsell, and others.

Season All Season
Date 2008-01-17
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Keywords: Climatic zones

PAL Question:

I have seen references to Climate Zones or Plant Zones, could you please point me to a reference that would help me to find what areas of the country or climates that these zones refer to.

View Answer:

The handiest way to tell what part of the country a given zone covers is to consult a map. Here are two web sites that will help you do just that.

The National Arbor Day Foundation web site has a concise explanation of Hardiness Zones. Just enter your ZIP code in the search box and press the Look it Up button. A map will pop up telling you the zone in which your town falls.

In case you would like to compare the above site to another one, The United States National Arboretum has a clickable map that will also allow you to determine your zone. Just click on your state on the map or, alternatively, click on the state abbreviation below the map and you will be able to tell what zones apply to your area.

The American Horticultural Society has produced a "heat zone" map, which serves to address drought and heat tolerance in different regions.

If you are on the West Coast, you may find the Sunset climate zones more helpful, as they take into account other variables besides just winter minimum temperatures. Search for keyword 'climate' or 'zones.'

Another great resource at the library is The New Sunset Western Garden Book, edited by Kathleen Norris Brenzel. Menlo Park, CA : Sunset Pub. Corp., 2012.

Season All Season
Date 2006-12-08
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Keywords: Plant care, Jasminum

PAL Question:

I have a question about the common jasmine plant. Can it be planted in a pot and left on the patio all year round? It will be attached to a fixed trellis. What should we do to protect the plant in the winter?

We live in Langley BC, so our weather is quite similar to yours.

View Answer:

The American Horticulture Society's A to Z Plant Encyclopedia reports that Common Jasmine (Jasminum officinale) is only hardy to zone 9. (Seattle is zone 8, Langley may be a touch cooler)

However, local author (I believe she lives in BC) Christine Allen reports that Jasminum officinale, also known as poet's jasmine, is hardy in our climate if protected from cold, drying winter winds. I think if you move your pot against a wall out of the wind you should be ok.

Season All Season
Date 2006-05-26
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Keywords: Origanum, Herbs

PAL Question:

I have marjoram and/or oregano growing all over. I like it and use it as filler, left over from herbs I bought several years ago. But, to cut them and use for seasoning, I don't know which is which and they don't seem to be so fragrant. Should I just start over and buy new plants to know what I have? How can I tell the difference between the two plants?

View Answer:

Everytime I get this question (this almost qualifies for a frequently asked question) I have to look it up again because even the authorities get mixed up.

Oregano and marjoram are the same genus, Origanum, but different species/hybrids.Marjoram usually refers to Origanum majorana. Marjoram leaves tend to be more gray green in color than oregano, and the leaves are generally smaller. Oregano usually refers to Origanum vulgare. It has a more pungent flavor, while marjoram is sweeter and milder. If you are interested in learning more, this guide from the Herb Society of America goes into great depth on oregano and marjoram.

The short answer to your question is yes, you should start over with new plants if you want good flavored herbs. You could bring in a sample to the Hyde Herbarium here at the Center for Urban Horticulture, 3501 NE 41st St. Seattle.

Season All Season
Date 2008-01-17
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Keywords: Pyrus, Fall foliage

PAL Question:

Which semi-dwarf pear tree should I plant to get good fall color? I want to eat the fruit and have beautiful yellow to red fall leaves in my landscape.

View Answer:

Not many of our resources on pears describe the color of the fall foliage, as they tend to focus on the taste and appearance of the fruit. However, I did consult Lee Reich's Landscaping with Fruit (Storey Publishing, 2009), and on page 146 he features "seasons of visual interest." Here is what the author has to say:
"Come autumn, leaves of many pear varieties, including many Asian varieties and such Europeans as 'Colmar d'Ete,' 'Durandeau,' and 'Triomphe de Vienne,' take on very attractive coloration. Ripening pears among the leaves, especially yellow varieties, also contribute to the show."

I suspect that the varieties mentioned above are heritage varieties that may be challenging to find. You might find these links of interest:

By doing an internet search, I came across a reference in a book entitled Growing Shrubs and Small Trees in Cold Climates by Debbie Lonnee et al. On page 233, the authors mention that the variety 'Golden Spice' has "nice fall color." The 'Luscious' variety is said to "turn a nice red in fall." This book confirms what I have read elsewhere, which is that ornamental pear trees are better known for their fall color.

Another approach would be to talk to pear vendors at farmers markets or talk directly to fruit farmers in your area, and ask if there are particular varieties which are notable for their autumn foliage.

An additional consideration is choosing pears which are late-ripening. If you want the fall color to coincide with the pears, you should probably choose a late-ripening variety. Pears are harvested before they are fully ripe, so later varieties will give you a better chance of night temperatures being sufficiently cool for leaves to begin changing color. Oregon State University's publication, "Picking and Ripening Apples and Pears," by R. L. Stebbins et al., has additional details on different pear varieties.

Season Fall
Date 2011-11-02
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Keywords: Magnolia grandiflora, Trees--Pacific Northwest

PAL Question:

I was reading an article in the local paper that mentioned Magnolia grandiflora 'Alta' and was hoping that you could tell me more about and its hardiness in the Pacific Northwest and what its mature dimensions would be.

View Answer:

Magnolia grandiflora 'Alta' is a trademarked Monrovia introduction. According to their website, it is "very slow growing to 20 ft. tall, 9 ft. wide in 10 years." Since this is a relatively recent introduction, there is not going to be much information about its hardiness in our area until more gardeners have grown it and shared their experiences. The longevity of the species Magnolia grandiflora and its cultivars can only be estimated (between 50-150 years, according to SelecTree.) Trees grown in urban settings are often affected by root disturbance, pollution, and the like, so their lives may be somewhat toward the short end of the expectancy range.

The local website of Great Plant Picks lists two different cultivars of Magnolia grandiflora, which may give you some idea of how well they do in our area. Here is an excerpt:

"Provide southern magnolias with good drainage and full to partial sun. They thrive in hot spots, where the extra heat encourages better flowering. These flowering evergreens prefer well-drained, sandy soil, but they tolerate average garden soil. Best growth and flowering requires occasional summer watering, but once established, southern magnolias withstand considerable drought. Garden gently under magnolias, for they have fleshy roots that can easily be damaged. The best approach for companions plants is to tuck in natural spreaders and let them flourish untouched."

From my observations, they do not do well in the occasional winters when we have heavy snowfall, as their evergreen leaf-laden branches are prone to breaking under the weight of snow. Otherwise, they seem to survive here.

Season All Season
Date 2008-01-24
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Keywords: Grapes--Diseases and pests, Vitis, Viticulture

PAL Question:

I am looking to install wine-producing grapes in my back yard, but I want to purchase vines from a reputable company, especially since I want to minimize the chance of exposure to Phylloxera. Where would you recommend I shop for the 12-20 vines I would like to install in my back yard?

View Answer:

While I cannot guarantee that any of these nurseries sell stock that is free of Phylloxera, here are three reputable nurseries that may have what you are looking for:

Raintree Nursery
Burnt Ridge Nursery & Orchards
Cloud Mountain Farm

Source: Susan Hill. The Pacific Northwest Plant Locator 2000-2001.

If you would like to know more about Phylloxera, Oregon State University's booklet, Grape Phylloxera: Biology and Management in the Pacific Northwest discusses the subject in great detail.

Season All Season
Date 2006-12-08
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Keywords: Perovskia, Lavandula, Botanical nomenclature

PAL Question:

I am looking for rare Siberian lavender. Can you help?

View Answer:

I think what you mean is Russian sage, Perovskia atriplicifolia. You might want to phone your favorite retail nursery to see whether they carry it (it is very popular). If it is not available, here are two Oregon nurseries that list it in their current catalogs:

Forestfarm in Williams, OR.
Joy Creek Nursery in Scappoose, OR

The following article from University of Illinois Champaign-Urbana Extension describes the confusion between Russian sage and 'Siberian lavender:'
"To the best of my knowledge, there is no such plant as Siberian Lavender. I have heard of English lavender, French lavender and Spanish lavender. By law all of these offers must list the Latin name of the plant; although sometimes it is in the tiniest of print. Check the ad again and see if you can find the words Perovskia atriplicifolia anywhere in the ad. Russian sage. It is a really fine plant, but it is not lavender. It does not look like lavender and it does not smell like lavender.
Do your homework and read the fine print. I know many people are not familiar with botanical names, but that is the only way to know what you are getting. Once you know the botanical name, even if you cannot pronounce it, you can find information about the plant. Botanical names are unique. Common names can be very misleading. A good example is an ad I saw recently in the newspaper. It was touting the luxurious beauty and fragrance of Siberian lavender. I had never heard of anything called Siberian lavender so I kept reading. The ad stated (with lots of exclamation points) how Siberian lavender produces thousands of flowers and has the delicate scent of lavender perfume year after year. Wow, sounds pretty fantastic. I continued to look to find the botanical name. In the minuscule fine print it said, Variety: perovskia atripliafolia (which I assume to be the misspelling of Perovskia atriplicifolia) also known as Russian sage. Russian sage is a nice perennial plant with silvery white leaves and soft bluish-purple flowers held in loose spikes. However, even from far away on a foggy day I doubt Russian sage would hold even a slight resemblance to lavender. Russian sage does have a fragrance, but it is more reminiscent of sage than of lavender."

Season All Season
Date 2008-01-24
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Keywords: Shade trees, Ornamental evergreens

PAL Question:

We would like to plant a special evergreen tree that would be a large heirloom or heritage tree. We would like this to be the centerpiece of our back yard. We know the type of trees that typically fall into this category will be slow-growing, so we want to plant it soon so that it will be big enough for our grandchildren to climb in, swing from, play under, etc.

We would like a tree that is quite large and wide (possibly even wider than it is tall, around 40 feet tall x 40+ feet wide), with branches that start relatively low on the trunk, but do not go all the way to the ground (so you could both climb into it and have a picnic table under it).

View Answer:

I recommend visiting your local arboretum. If you are in the Seattle area, the Washington Park Arboretum is one place where you will find many examples of mature trees, some of which are coniferous evergreens, some of which are broadleaf evergreens. There are also many useful books to help you select the tree that best suits your needs. Since you are interested in evergreens, I particularly recommend Richard Bitner's Conifers for Gardens: An Illustrated Encyclopedia (Timber Press, 2007) and Portland, Oregon author Sean Hogan's Trees for All Seasons: Broadleaved Evergreens for Temperate Climates (Timber Press, 2008).

Here are websites that are useful in narrowing down tree lists once you have a few ideas in mind. (Note: Some of the sites have a zone option, i.e. where the trees grow best. Seattle is in USDA Zone 8b & Sunset Zone 5). In some cases, you can narrow down the selection even further, by selecting tree attributes (see the SelecTree site below).

Virginia Tech's Department of Forest Biology and Environmental Conservation has a series of Tree Identification Fact Sheets. This site is best for descriptions when you already have a species in mind.

Search the SelecTree database from CalPoly.
The best way to get a good list (with numerous options) is to click on Select Tree by Attribute.

A classic source is the USDA Forest Service internet version of Silvics of North America. It will not help with selection since you will need to know what species you want, but it will provide more information than you will ever need.

Season All Season
Date 2008-01-24
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Keywords: Aphids, Integrated pest management, Viburnum

PAL Question:

I have a small snowball bush that I planted three years ago. Each spring this plant is inundated with more and more ants and aphids. I try to garden organically and could use Safer Soap on it, but it is large and the leaves are all curled under and withering from the insects. Is there anything other than Safer Soap that I could use to help the plant, either systemic or otherwise?

View Answer:

Following are the best sources I have found about environmentally friendly control of aphids.

Aphids (order Homoptera)

Host/Site:
Almost all plants have an aphid species that may occasionally feed on them. Many aphid species attack several plants rather than having only one host. Trees (esp. birch, beech, maple, apple, peach, apple, plum, cherry, spruce, dogwood, willow); annuals (esp. nasturtium, snapdragon); perennials (esp. lupine, roses, lilies, begonias, columbine); vegetables (esp. peas, beans, brassicas, lettuce, spinach); fruit (esp. apple, peach, cherry).

Identification/appearance:
Small (2 mm long), pear-shaped, softbodied insects in a range of colors (green, brown, red, yellow, black). Most are wingless, but winged aphids appear at certain times, especially when populations are high or during spring or fall. A few species appear waxy or woolly. A magnifying glass will reveal the long, slender mouth parts used to suck plant fluids. Aphids are usually found in clusters, especially on new growth. Signs of aphid infestations include sticky honeydew on leaves or under plants, distortion of leaves, stunting of shoots, or large numbers of ants on the plant.

Life Cycle:
Overwintered eggs of some common garden species hatch in spring. These wingless females reproduce asexually, bearing live young (up to 80 per week) that already have the next generation developing inside. Young aphids, called nymphs, molt four times before becoming adults. There is no pupal stage. This simple, rapid reproduction allows for very large population increases in a short time. Late in fall, males and females are produced, mate, and the females subsequently lay eggs. Winged aphids may appear at certain times, allowing the colony to move to other locations. Not all aphid types have this reproductive pattern, but many do.

Natural Enemies:
Aphids have many natural enemies, including birds, spiders, ladybird beetles, lacewings, syrphid fly larvae, and braconid wasps. A naturally occurring fungal disease can also kill aphids when conditions are right. Ants have a symbiotic relationship with aphids: ants milk the aphids for honeydew while protecting the aphids from natural enemies.

Monitoring:
Check plants often, since aphid populations can rise rapidly. Inspect growing tips and undersides of leaves. On trees, clip off leaves from several parts of the tree to look for aphids. If you see large numbers of ants on tree trunks, check for aphids on limbs and leaves. Look also for associated signs, such as yellowed leaves, stunted or distorted growth, or dripping honeydew. Sticky traps can be used to monitor for winged aphids. Check for signs of predators (named under Natural Enemies above), aphids that have been parasitized (look for a small exit hole on a dead, brown aphid body), or that have been killed by disease. Substantial numbers of any of these natural control factors can mean that population numbers will fall rapidly without the need for treatment. Because of the rapid changes that can occur in aphid populations, it is important to record monitoring data to detect changes due to predators or treatments.

Action Threshold:
Due to the incredibly high numbers that may be present, counting individual aphids is usually not practical. Action thresholds can be based on general descriptions of aphid density, plant damage such as stunted or distorted growth, or unacceptable amounts of honeydew beneath trees. Treatment should be triggered by rapidly rising numbers, unacceptable plant damage, or by honeydew falling on structures and people. Aphids seldom kill a plant, but they can cause defoliation. They also carry diseases from one plant to another. It is usually not necessary or even desirable to treat at the first sign of aphids, since low populations are needed to sustain predators.

Cultural/Physical Controls:
Plant selection: If possible, avoid or consider replacing varieties such as birch that have ongoing, serious aphid problems. Check transplants for aphids and remove them before planting.

Water spray: A strong blast of water knocks aphids from the plant, and most will not return. Water also helps rinse off the honeydew. Do this early in the day to allow leaves to dry and minimize fungal diseases.

Pruning: Where high aphid populations are localized on a few curled leaves or new shoots, prune these areas out and drop in soapy water to kill the aphids.

Fertilization control: High nitrogen levels favor aphid reproduction. Avoid over-fertilization and use slow-release rather than highly soluble fertilizers.

Sticky or teflon barriers: If you see ants crawling up the trunk of trees or other woody plants, place a band of sticky material (such as Tanglefoot or Stik-Em) around the trunk. Place a protective band of fabric tree wrap or duct tape underneath the barrier first. Teflon tape barriers may also be effective. Prune out branches touching the ground, buildings, or other plants.

Biological Controls:
Since aphids have many natural enemies, biological control usually means protecting these enemies from ants and avoiding broadspectrum pesticides that kill beneficial insects. Recognize that predator populations usually lag behind aphid populations in time. A number of aphid enemies can be purchased for introduction into landscapes. Ladybird beetles, lacewings, and parasitic wasps and flies are all available. Although such introduced predators may not remain where released, some benefit is likely, especially if releases are staggered in time. Many of the natural predators of the aphid are especially attracted to a garden with plants in the Umbelliferae family, such as angelica, sweet cicely, dill, and Queen Anne's lace. The flowers of these plants provide a good food source for insects, especially parasitic wasps, who may stay to prey on some aphids as well.

Chemical Controls:
Insecticidal soap is widely recognized as the least-toxic chemical aphid control. Although its effect is temporary, it can help to bring aphid numbers down so that natural enemies can take care of them. Repeat applications within a few days may be necessary. Soap works only by direct contact with the insects. Be sure to cover both sides of the leaves. Although readily biodegradable, soaps are highly toxic to fish, so avoid runoff or direct application to water. Avoid using when temperature exceeds 90 degrees F.

Oil sprays:
Supreme or superior-type oils will help to kill overwintering aphid eggs on fruit trees if applied as a delayed dormant application in early spring. Although perhaps not justified for aphid control alone, oils can also control other overwintering fruit pests. Oils may, however, kill some beneficial species. Summer weight oils are also available, but they can burn tender leaves when applied in hot sun.

Conventional chemical control:
Foliar applied insecticides (malathion, diazinon, carbaryl, pyrethrin) are broad spectrum and will kill beneficial insects. They should be avoided, especially in home gardens and landscapes. Remember that allowing some aphid population in the garden helps to keep predators available.

ProIPM Integrated Pest Management Solutions for the Landscaping Professional
The Green Gardening Program is a collaborative effort of Seattle Tilth, Washington Toxics Coalition, and WSU Cooperative Extension, King County.
Sponsored by the Seattle Public Utilities in an effort to promote alternatives to lawn and garden chemicals.
Funded by the Local Hazardous Waste Management Program in King County.
Written by Philip Dickey, Graphic Design by Cath Carine, CC Design

Pest description and crop damage:
Aphids are soft-bodied insects that typically feed on leaves and succulent stems. They may vary in color from pale green or reddish to dark or black. Aphids are usually less than 1/8 inch in length.

Feeding damage to the plant is usually minor, although some leaf and shoot distortion can occur if populations are high. Aphids also produce honeydew, a sweet, sticky secretion that collects on plant tissues and encourages growth of a black sooty mold. This can interfere with photosynthesis of the plant. Honeydew is also a nuisance when it falls on decks, cars, or other landscape surfaces. They are a problem in early summer.

Biology and life history:
Most species of aphids have similar life cycles. Aphid females give birth to live offspring all year without mating. When other hosts are not available, aphids live on a wide variety of weeds. Aphids usually are found in colonies on new growth, the underside of leaves, and near flower and fruit clusters. In summer and fall, aphids may produce winged females and, later, winged males. They mate and produce eggs for overwintering, especially in colder climates. Otherwise, adult aphids overwinter on crops, weeds, or trees. There may be as few as 2 or as many as 16 generations each year, depending on the species and climate.

Management & biological control:
Aphids have many natural enemies, including lady beetles, syrphid fly larvae, and green lacewings. Avoid broad-spectrum insecticide applications that would disrupt these controls.

Management & cultural control:
Wash aphids from plants with a strong stream of water or by hand-wiping. Aphid populations tend to be higher in plants that are fertilized liberally with nitrogen and heavily watered, as this produces flushes of succulent growth. Avoid excessive watering, and use slow-release or organic sources of nitrogen. Control ants, which farm aphids and protect them from predators in order to harvest their honeydew.

Management & chemical control (home):
It is important to cover foliage thoroughly, including lower leaf surfaces.
1. Beauveria bassiana
2. horticultural oil
3. insecticidal soap

Source:
http://pnwpest.org/pnw/insects

Season All Season
Date 2006-11-14
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Keywords: Acer circinatum, Fall foliage

PAL Question:

I have a vine maple tree whose leaves turn a very plain, rather ugly brown in the fall. It gets full sun from about noon until sunset. From what I have read, its leaves should turn red, orange, and yellow. What can I do to trigger this? I am thinking of how Hydrangeas are different colors depending on the acidity of the soil. I would like a tree with attractive fall color. I have also read it likes moist places in the shade, and it has not had that environment in my yard. Could the amount of water it gets in the summer, or lack of water, be affecting this?

View Answer:

According to J. Harris in The Gardeners Guide to Growing Maples (2000, p. 119), "Autumn color is due to a chemical change in the leaves and a combination of the remains of the chlorophyll grains and a substance called anthocyanin. The color assumed by leaves depends on soil and air conditions and on the amount of moisture. If conditions are very dry in the autumn, then the color will not last for long. After a frost, colors appear more intense, but the frost can check activity. It will also not be so good in very wet conditions."

The National Arboretum provides a complete explanation of why autumn leaves turn color.

There is an excellent article in the Seattle Times (September 25, 2008) by former Washington Park Arboretum Collections Manager Randall Hitchin which also describes this process.

There are other possibilities why your vine maple is not producing good fall color:

1. It might be getting too much light. The natural habitat for the vine maple is under an overstory of large conifers (Japanese Maples, by J. Vertrees, 2001, p. 247). Afternoon sun is the most intense and could be stressing the tree. Harris (2000) notes that while tree-like species prefer open sites, woodland conditions and dappled shade are ideal environments for shrubby maples. (Harris., p. 118).

2. Other than light, the environment might be a little off. Vertrees (2000, p. 247) notes that with vine maples, intense color does not develop in environments where abundant moisture and fertility keep the trees from being under stress, i.e., they need stress to produce good color.

3. Trees of the same species will exhibit different fall colors depending on the growing environment and peculiarities of each individual tree. (As identical twins can be quite different). When selecting a tree for fall color, it is best to first view it in autumn -- then remember it will change somewhat when it is installed in a new home.

It is not likely that changing soil pH will have an effect. I have been disappointed in fall color a couple of times and finally replaced the trees -- after viewing them in full color in the nurseries.

Season Fall
Date 2008-01-24
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Keywords: Crataegus, Trees--Diseases and pests--Washington

PAL Question:

My Hawthorn tree has black spots on the leaves. Can you tell me what disease this might be? In general, what diseases affect Hawthorn trees?

View Answer:

To learn about diseases most common to Hawthorns in the Pacific Northwest, visit the Pacific Northwest Plant Disease Management Handbook and search on the word hawthorn. You will get a list of several diseases that commonly affect hawthorns; click on any of them for a full explanation.

Season All Season
Date 2008-01-24
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Keywords: Malus, Trees--Diseases and pests--Washington

PAL Question:

My Fuji tree is infected with Cherry Bark Tortrix. Can the branches, leaves, and bark be used as mulch? What should be done with the wood? Can it be stored, and burned in our fireplace?

View Answer:

The leaves and branches can be mulched. The wood can be used, but it is a good idea to strip the logs of the bark and store the wood barkless. Removing the bark will destroy most of the caterpillars in the process. The wood is easier to chop when the bark has been removed, too! If you cannot remove the bark, use a mallet to tap the bark where ever you see galleries. This will most likely squash the caterpillars that are still in the wood.

Season All Season
Date 2006-06-01
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Keywords: Trees--Wounds and injuries, Neighbor law

PAL Question:

How can I find out if my Monkey Puzzle tree was poisoned by my neighbors? I found 6 holes drilled into it on their side.

View Answer:

Before assuming the tree has been poisoned, make sure that the holes were not actually caused by woodpeckers or flickers, since this is common behavior among such birds--and less common behavior among neighbors, one would hope!

In order to determine for sure whether your trees have been poisoned, you may wish to consider contacting a certified arborist. For a fee, an arborist will visit your property and make a diagnosis or recommend another plan of action.

For a list of arborists, contact Plant Amnesty, an organization of arborists and vetted gardeners at 206-783-9813 or visit the Pacific Northwest Chapter of the International Society of Arboriculture.

To pursue a legal solution to the problem contact the King County Law Library where County law librarians will be happy to help you with your research.

The book Neighbor Law by Emily Doskow and Lina Guillen (Nolo Press, 2014) is also a useful resource.

Season All Season
Date 2008-01-24
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Keywords: Weigela, Color guides, Dwarf shrubs, Nandina domestica, Ornamental shrubs

PAL Question:

Can you give me some information on Weigela Midnight Wine and dwarf Nandina? Are there any plant lists of purple-leafed shrubs?

View Answer:

Following is a good description of Weigela 'Midnight Wine.' The information comes from the Missouri Botanical Garden, so it is tested and accurate.

WEIGELA

'Elvera' Midnight Wine is a dwarf version of the popular Weigela 'Wine and Roses' (W760). It is a dense, rounded, low-growing deciduous shrub that typically grows to only 1.5-2 feet tall and as wide. Features profuse reddish-pink flowers and burgundy-purple foliage. Reddish-pink, funnel-shaped flowers (to 1.25 inches long) appear singly or in clusters along the branches of the previous year's growth in mid- to late spring, with sparse and scattered repeat bloom often occurring on new growth as the summer progresses. Elliptic to obovate, glossy, burgundy-purple leaves (to 3 inches long) turn very dark purple in autumn. Hummingbirds are attracted to the flowers. Original cultivar name is 'Elvera', but plants are being marketed under the registered trademark name of Midnight Wine. U. S. Plant Patent #12,217 issued November 20, 2001. Source.

NANDINA

There are several varieties of dwarf Nandina, such as 'Harbour Dwarf,' 'Firepower,' 'Nana,' and 'Nana purpurea.' University of Florida Extension has a feature on dwarf Nandina on their website. There are also plants available from nurseries such as Forestfarm Nursery and Greer Gardens in Oregon, and Whitney Gardens in Washington.

PLANT SUGGESTIONS As far as lists of plants with purple foliage, you should find a wealth of information in the book Black Magic and Purple Passion, by Karen Platt, 2004. There are also lists online, such as this page from Iowa State University Extension, entitled "A Passion for Purple." You can also search Royal Horticultural Society's Plant Selector and other similar resources by leaf color.

Season All Season
Date 2007-05-30
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Keywords: Cornaceae (Dogwood family), Trees--Diseases and pests

PAL Question:

I live in Kitsap and my 50-year old maple is dying -- what should I do?

Also, my Dogwood trees seem to be infected with anthracnose. Can you give me some information about this disease?

View Answer:

To get some information about your maple, you can consult with a Master Gardener at a WSU Kitsap County Extension Diagnostic Clinic.

Regarding dogwood anthracnose (Discula destructiva), it is a shame that so many of these beautiful trees are infected. You may be somewhat reassured to know that although the disease often causes tree death in the northeastern U.S., here in the Pacific Northwest, many trees survive. Douglas Justice, Curator of Collections at University of British Columbia Botanical Garden, discusses this on the UBC discussion forum.
Excerpt:
"Weather is probably the deciding factor in infection. A cool, wet period seems to be most conducive to infection, and such factors probably have to coincide with a specific time of tissue susceptibility. In other words, the conditions have to be "just right" for the disease to take off and become established. However, it is well documented that stress predisposes plants to disease susceptibility. Stressors for Cornus nuttallii (Pacific dogwood) would include compacted soil, poor drainage, full exposure with overly dry soil (C. nuttallii is adapted to a summer drought regime, but let's be reasonable!) and wet soil in summer (e.g., irrigated soil -- see previous comment). Nearly all the local anthracnose-affected dogwoods recovered, including the wild natives and the even some of the more severely affected C. florida (eastern dogwood). Anthracnose has visited us subsequently, but mostly only on C. florida and urban C. nuttallii. This suggests that the there isn't much anyone can do to prevent the disease from occurring and that as along as trees aren't overly stressed, they will eventually recover. "

A U.S. Forest Service article entitled How to Identify and Control Dogwood Anthracnose includes images which may help you to determine if your tree has anthracnose.

Master Garden Products.com provides a short article about dogwood anthracnose that contains a What to Do list.

University of Maryland College Home and Garden Information Center's Integrated Pest Management Series HP #12 offers information about dogwood diseases and pests, including anthracnose.

Oregon State University Extension's Online Guide to Plant Disease Control describes cultural controls for anthracnose. There is also an extensive list of chemical controls, which you may choose to ignore after reading Douglas Justice's comments from the UBC discussion forum mentioned earlier:
"The application of fungicides is probably a waste of money and also likely counter-productive, particularly with a systemic such a benomyl, which will kill most of the good fungi, but probably not the target pathogen. Common fungal pathogens frequently develop resistance to this fungicide."



Season All Season
Date 2008-01-24
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Keywords: Transplanting, Bamboo

PAL Question:

I transplanted some bamboo and now some of it is dying. Can you give me some information on how to transplant bamboo correctly?

View Answer:

The following is an excerpt from the American Bamboo Society webpage.

Q. How do I transplant part of a large clump of bamboo?
Transplanting is hard work and involves digging a large chunk of root ball out of the ground. Never transplant bamboo when it is shooting. Dig bamboo either very early in the spring before there's any chance of shooting or wait for the growth period to be over late in the autumn. You should look for a clump of culms that has come up in the last year or so and which includes at least three or four healthy-looking culms. A good size for the clump would be at least two feet in diameter. Bamboo roots (rhizomes) are tough but must not be allowed to dry out even for a few minutes. You may have to use a very sharp shovel, ax or saw to separate the roots from the rest of the grove. If you will be transferring the division by truck, then water the leaves and roots well, wrap the whole thing in plastic and get it into the ground as quickly as possible.

Season All Season
Date 2006-06-02
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Keywords: Antirrhinum, Capsicum, Vegetable seedlings, Seedlings, Tomatoes

PAL Question:

I started some seedlings of tomato, pepper, snapdragon and lettuce in my sunroom under shop lights in peat pots. The temperature in the room is in the 60s at night and 70-80 in the day. I keep the soil evenly moist, but after 3 weeks, none of the seedlings that have germinated have true leaves. No secondary leaves of any kind. I cannot imagine why this would be under those conditions. Can you help me?

View Answer:

There are a number of variables that may be at work here. Are the seeds new? If not, were they stored properly? Also, seeds have varying lifespans. Some seeds require light to germinate and others do not. Some must be sown on or near the surface, and others must be sown more deeply. Seeds require varying degrees of heat. Oxygen is another requirement: is the seed-sowing mixture in your pots compacted? That might prevent germination. The steady moisture you are providing is good, and the temperature in the room is about right for most seeds.

University of New Hampshire Extension has useful general guidelines for starting seeds indoors.

The temperature of the water or the time of day in which the watering takes place may be influencing the growth of the plants. According to an Ed Hume's Garden Questions Archives article entitled, Starting Vegetable Seeds Indoors, seedlings should be watered with water that is just a little warmer than room temperature. If the water being used is too cold or if watering occurs in the evening as the temperature of the room drops, this could be slowing the plant growth.

I am wondering if the day time temperatures are too high. To quote from The Seed Starter's Handbook by Nancy Bubel (Rodale Press, 1988): "Plants grown indoors in warm rooms put on weak, spindly, sappy growth that is difficult to manage. Start seeds warm and grow seedlings cool."

Lastly, Starting from Seed by Karan Davis Cutler (Brooklyn Botanic Garden, 1998) says: "Since both heat and light fuel plant growth, the relationship between the two is critical. A common mistake among home gardeners is to keep plants at too high a temperature for the amount of light they receive. What often happens is that the gardener tries to compensate for slow growth with more fertilizer and higher temperatures. The result is limp, leggy seedlings that are hard put to cope with outdoor conditions. On cloudy days, the experienced gardener lowers the temperature to compensate for the lower light levels. While every plant has a temperature range it likes best, within that range, the cooler you keep the temperature, the better off the plant will be. Do not take things too far, though. A combination of low temperature, low light and overwatering is ideal for the development of damping-off fungus."

Season All Season
Date 2008-01-24
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Keywords: Lolium, Ajuga, Vinca, Hedera helix, Festuca, Arctostaphylos, Achillea, Grass varieties, Land treatment of wastewater, Turfgrasses, Ornamental grasses, Landscaping drain fields

PAL Question:

We have a new house that we have to landscape around. The biggest problem is that we have to be careful what we plan due to the septic system. It is an evaporation system, with two huge cement tanks buried under the ground in the front of the house and plastic pipes running through the side yard. We are planting grass in a rectangle right above the biggest bunch of the plastic pipes, but what can go around it or by the cement tanks that will not grow long roots and dig into it? In looking at the planting information on the packages and in my Western Garden Book, nothing seems to mention root depth.

View Answer:

Below is an article entitled What to Plant Over the Septic System by Mary Robson (originally published in her Regional Garden Column for Washington State University Extension, December 6, 1998):

"As more and more people move into rural areas, questions about septic systems and landscaping have become quite common. This column deals with some of the basics. A new brochure from Washington Sea Grant called: Landscaping your Septic System, offers considerable detail on the subject and provided much of this material.

"First, be sure that the septic field is clearly identified, and you know where the reserve area is. Keep all construction away from these areas. Understanding the functioning of the system is vital. Get information. (Some of it is available in video form.) The drainfield will not work well if overloaded with extra surface water, so be certain that it is not in the path of downspout run off or irrigation systems.

"Sunlight and air circulation also help the drainfield perform properly. Avoid surrounding it with tall trees. (Some shade is fine, but you would not plant an oak on the edge of a drainfield.) Set up some barriers so that it is not compacted by frequent foot traffic. Occasional mowing or moving through the field to check the system is certainly fine, but you do not want the drainfield in the middle of a heavily used path.

"There are advantages to using plants over the drainfield. Plants do help provide oxygen exchange and contribute to evaporation necessary in the drainfield area. Choose plants with shallow, non-invasive roots. You do not want breakage or damage in pipes from root intrusions.

"Grasses are most commonly recommended for the septic area. Lawn can be attractive. Do not overload the system by watering it a lot. Meadow grasses or a mixture of turf grasses like perennial rye and some broadleaf flowers (such as yarrow) can also look good and require little maintenance. Several mixes sold as Eco-Turf or Fleur de Lawn have these components.
"Small, shallow-rooted ornamental grasses (for instance, Festuca ovina 'Glauca' 4-10 inches) can also be good looking. Very tall grasses like Stipa gigantea are not appropriate. Avoid over-active plants like English ivy (Hedera helix), which is becoming a menace in forested areas by moving in and stifling trees.

"Edible crops are not suggested. Vegetable gardening requires frequent cultivation, and digging in the drainfield area is inadvisable. Also, the brochure notes that: Sewage effluent is distributed through the soil in the drainfield area. Any root vegetables planted in this area may be directly exposed to septic tank effluent.

"Other possibilities are low-growing ground covers. Some, such as bugle weed (Ajuga reptans) and vinca (Vinca minor) grow vigorously and would fill in quickly. The native kinnickinnick (Arctostaphylos uva-ursi) grows well in full sun but is slow to establish. A mulch around the plants may help with weed control while the plants spread.

"The green growing layer over the septic tank helps the system to function, adds to the appearance of the landscape, and should, ideally, be set up to allow easy monitoring and maintenance. Keep landscaping simple and straightforward, remembering that the object is the good performance of the system."

To get more information on septic systems, contact your local health department. The brochure Landscaping Your Septic System (pdf) is available through the Sea Grant Program.

Here are links to publications that might also be helpful:
Mounds: A Septic System Alternative
Understanding and Caring for Your Sand Filter System
Care and Feeding of Septic Tanks

Season All Season
Date 2007-04-10
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Keywords: Persicaria

PAL Question:

I have a something called Chevron Plant in my yard. There is a distinct v-shape pattern on the upper side of the leaf, and it gets red tiny flowers in the spring/summer time. It grew about 1.2 in height. Can you tell more about this plant?

View Answer:

Chevron Plant is not a known common name, but the perennial Persicaria virginiana (and its cultivars) is notable for the chevron-shaped markings on its leaves. A more familiar common name is Knotweed (and it is in the same family as the invasive Japanese knotweed, sharing some of that plant's tendency to spread). The genus includes 50-80 species of annuals and perennials, often rhizomatous (spreading by roots) or stonoliferous (spreading by runners). They may be evergreen, semi-evergreen, or deciduous. There are several varieties with interesting v-shaped leaf patterns, and some have red flowers. To verify whether this is what you have, try searching the plant's botanical name on Google or another search engine and then click on Images and search for Persicaria.

If that is correct, they are best grown in any moist soil in full sun to part shade. If they get out of control they can be cut to the ground in late fall or winter. Some species can be aggressive and even officially invasive and need to be controlled.

If that is NOT your plant, the Hyde Herbarium at the Center for Urban Horticulture can provide a positive identification.

There may be people at your local nursery who can help you as well.

Season All Season
Date 2008-01-24
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Keywords: Nymphaea, Pond plants

PAL Question:

I am looking for information about planting floating emergent plants (e.g., water shield, yellow pond lily) in natural ponds. If planting young plant material in the soil, what is the recommended water depth? Is it okay to submerge the entire shoot? If yes, what is a safe depth from top of shoot to water surface?

View Answer:

There are several different types of plants that are grown in ponds. A great resource on planting floating plants is The Water Gardener's Bible: A step-by-step guide to building, planting, stocking, and maintaining a backyard water garden by Ben Helm and Kelly Billing (Rodale Inc., 2008). In the book they explain that floating plants will either float on the pond surface or be slightly submerged. The most popular floating plants are Frog's bit (Hydrocharis morsus-ranae), Water hyacinth (Eichornia crassipes), Water chestnut (Trapa natans), and Water soldier (Pistia stratiotes). They also explain submerged plants that will inhabit a pond at all levels, from those whose roots sit on the bottom to those that emerge from the pond, getting only their feet wet. For planting a water lily, place on a stack of bricks in the position where the lily will be sited, so that the top of the planted basket is no more than 1 inch (3 cm) below the surface. As the leaves start to extend, remove the bricks until the basket is on the pond bottom.

Another great book is Plants for Water Gardens: The Complete Guide to Aquatic Plants by Helen Nash and Steve Stroupe (Sterling, 1998). The book contains a huge list of a variety of lily plants and specifications for planting and survival.

The University of Illinois Extension has a website on Water Gardening that has useful information on planting aquatic plants. You may want to check your local list of invasive species before planting.

Season All Season
Date 2008-01-24
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Keywords: Persea, Plant care, Indoor gardening

PAL Question:

We have a large avocado plant (indoors) that is mystifying us. A couple months ago, it shed most of its leaves. The leaf would get droopy and the tips of the leaves would turn brown and dry out and then spread up the leaf. It got down to its last seven leaves and then seemed to stop, although all of these leaves have varying degrees of this leaf tip burn. Now over the last month or more, small new growth is appearing. They have not grown much at all and are only about an eighth of an inch long.

View Answer:

When growing an avocado (Persea species) indoors, you will need to be sure it is getting enough light. It is normal for the plant to drop older leaves. You should also keep the plant in a cool spot. According to The Houseplant Expert by D. G. Hessayon (Expert Books, 2001), your plant will do best if you repot it annually and pinch the tips to encourage bushy growth. Lee Reich discusses growing avocados indoors in an article for California Rare Fruit Growers. Here is an excerpt:

"Indoors, avocado plants are often gangly and sparse with leaves. One reason for the plant's gawky appearance indoors is light. Lack of sufficient light causes stems to stretch for it. Another reason is that avocados shed many buds along their stems, buds that might have grown into side branches. The result is a plant stretching out for light, sending out new growth mostly from the tips of the branches and shedding old leaves.
There are several things indoor gardeners can do to keep their plants more attractive. Most obvious is to give an avocado tree bright light. Also, the stretch for light is exaggerated when warmth stimulates growth, so the ideal spot for the plant is at the brightest window in the coolest room. Beyond that pruning back a stem or pinching out its growing tip stimulates branching by awaking dormant buds (not all are shed) further down the stem. There is nothing that can be done about the shedding of older leaves."

Grown outdoors in an agricultural setting, avocado plants sometimes get leaf tip burn from salt accumulation, as this article from California Rare Fruit Growers explains. If you are using especially salty tap water or overfertilizing your plant, that might be causing the burnt leaf tips. Other causes could be lack of water, too frequent light watering, or poorly draining soil.

Season All Season
Date 2008-01-24
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Keywords: Persea, Plant care, Avocado

PAL Question:

We know avocados like dry soil, but are there specific guidelines to follow?

View Answer:

"Growing conditions: Give avocado direct light; insufficient light will cause spindly growth. Provide a warm temperature and medium humidity. Keep the soil evenly moist but not wet and soggy. Fertilize once a month throughout the year... Use an all-purpose soil mix for repotting... Avocado is vulnerable to aphids, mealybugs, scale insects and thrips."
Source: The Time-Life Gardener's Guide; Foliage Houseplants, 1988, p. 125

"Growth habit: The avocado is a dense, evergreen tree, shedding many leaves in early spring. Growth is in frequent flushes during warm weather in southern regions with only one long flush per year in cooler areas."

"Foliage: Avocado leaves normally remain on the tree for 2 to 3 years."
Source: California Rare Fruit Growers Association website

Season All Season
Date 2008-01-24
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Keywords: Capsicum, Plant care

PAL Question:

For the past several years, I have tried to grow green peppers in our garden. The problem I have had is that they never grow very big, and the peppers never get much bigger than a small plum. I fertilize my garden, add compost, but still get small peppers.

View Answer:

Peppers are tricky in our climate. Quoting from Growing Vegetables West of the Cascades by Steve Solomon: These heat-loving plants do not readily adapt to climatic conditions north of the Yoncalla Valley..they are often irreversibly shocked by outdoor night-time temperatures below 55 F.Many gardeners make the mistake of setting peppers out at the same time as tomatoes right after there is no frost danger. This, however, will almost certainly expose them to overnight temperatures of 45 F or even worse. Any surprisingly cool night during June can shock peppers sufficiently to stop their growth for a time. North of Longview, Washington, and along the coast, only the hardiest pepper varieties will grow in cloches or greenhouses.
Source: Growing Vegetables West of the Cascades, by S. Solomon, 2000, p. 210, 236.

Oregon State University has an article entitled "Spice Up Your Garden with the Perfect Pepper" with a link to a guide to growing peppers in the Northwest.

Season All Season
Date 2008-01-24
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Keywords: Plant care, Narcissus

PAL Question:

I'm having a problem with my daffodils. They came up, but very few of them are blooming. This is the third year for them, and the worst turn out. They seem to be turning yellow at the bottom of the plant. They have multiplied well, and came up looking fine. Several of my friends are having the same problem. Could it be because they had so many days of below freezing weather this winter?

View Answer:

We found a helpful article from the American Daffodil Society. Potential causes for a lack of flowers include lack of fertilizer, too much nitrogen fertilizer, shade, competition with other plants, poor drainage, virus, foliage cut off too soon, need to be divided, or weather stress (such as early extreme heat) in the spring.

The cold weather should not have been a problem provided the bulbs were planted deep enough.

Season Spring
Date 2008-01-24
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Keywords: Soil testing

PAL Question:

I would like to know if there is some place where I can have my vegetable garden soil tested. For the last two years my vegetable plants were abysmal except for tomatoes and lettuce.

View Answer:

The Natural Lawn & Garden Hotline, sponsored by Seattle Public Utilities, provides the following recommendations on how to take a soil sample:
1) Take about 10 vertical slices of soil from the top 6-8 inches of your garden bed. If there is an area that you suspect to have problems, test this soil separately.
2) Place soil slices in a plastic bag and mix thoroughly. You are getting the average of the soil in your garden bed.
3) Take 1 cup from this mixture and dry it at room temperature. Do not dry in oven, on radiator or in microwave!
4) Put dry soil sample into a Ziploc bag and seal.
5) Label the outside of the Ziploc bag.
6) Mail to one of the soil testing labs below with completed order form and payment.

A WSU has a publication on soil testing for vegetable crops but it is mainly for agricultural growers.

Another option is the University of Massachusetts, Amherst soil testing laboratory.
This page has information and forms to send in with your samples.

The Soil and Plant Laboratory is based in California.

For testing of toxics see: King County's Resident Self-Testing Page.

A & L Western Laboratories, Inc. in Portland, OR can provide soil and plant analysis.

Season All Season
Date 2008-01-24
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Keywords: food safety, Malus domestica

PAL Question:

Is it safe to eat windfall apples if I cut away any sections that look bad? Or should I only use them in cooking?

View Answer:

If you want to err on the side of caution, you should use them neither for fresh eating nor for cooking. There is a toxin produced by fungi called Patulin which may be present in apples which have dropped from the tree and have been lying on the ground, according to a news release from University of Illinois Extension, dated September 21, 2012.

According to the Ontario Ministry of Agriculture, there are ways of diminishing the risk, but the processes involved are more appropriate to commercial apple processors than backyard orchardists. Excerpt:
"Current research suggests that varieties with an open calyx are a greater risk for patulin development within the core of the apple. In such a situation, damage to the fruit is not easily detected [...]

"Patulin is also destroyed by fermentation, which means it is not found in either alcoholic fruit beverages or vinegar produced by fruit juices. Patulin will however survive the pasteurization process if present in the juice."

The website of Food Safety Watch has more information about Patulin.

Season Fall
Date 2012-11-03
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Keywords: Rhododendrons--Varieties, Root weevils, Rhododendrons--Diseases and pests

PAL Question:

My rhodies are being devastated by root weevils. They have stripped many of the branches clean of their vegetation, and have destroyed ~50% of the remaining leaves. My rhodies look like they will require years to recover, if they ever do.

If I replace them with resistant varieties or plants that are not susceptible to these pests, will this eliminate the weevils?

View Answer:

Root weevils are the most common pest attacking Rhododendrons in the Pacific Northwest so they can only be temporarily eliminated from any garden. If the environment is right and their food source returns, so will the root weevils.

If you want to keep your current Rhododendrons, the weevils can be controlled if you're diligent (forever!?). An article by Caroline Cox in the summer 2005 issue of the Journal of Pesticide Reform discusses their control. However, it sounds as if you're willing to remove them and start fresh. Some of the most susceptible (host plants) are Rhododendron and Azalea, Heather, Salal, Manzanita and Kinnikinnick, Pieris, Maples, Viburnum, most Conifers, Astilbe, Cyclamen, Helleborus, Hosta and Primrose.
(Source: Root Weevils in the Nursery and Landscape; Identification and Control, by J. DeAngelis and G. Garth, EC 1485, Oregon State University Extension Service).

The extension bulletin from the Washington State University Extension website has an excellent list of resistant Rhododendron varieties.

Season All Season
Date 2008-01-24
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Keywords: Pruning shrubs, Cotinus coggygria, Cornaceae (Dogwood family), Trees--Diseases and pests

PAL Question:

Can you give me some general information about Dogwoods and anthracnose? Also, I would like to know about coppicing Cotinus coggygria.

View Answer:

Here is information about dogwoods and anthracnose:
The U.S. Forest Service article entitled How to Identify and Control Dogwood Anthracnose, may be of use. Although it is somewhat technical in its language, there are excellent pictures and a section about methods of control.
Master Garden Products.com provides a short article about Dogwood Anthracnose that contains a What to Do list.
Oregon State University Extension's Online Guide to Plant Disease Control provides a corroborating list of cultural controls for Anthracnose and adds an extensive list of chemical controls. It's always best to use cultural controls and avoid chemical ones if you can. Some dogwoods in the Pacific Northwest have been known to recover from anthracnose, according to Douglas Justice of University of British Columbia Botanical Garden.

The Royal Horticultural Society has useful general information on coppicing, and includes Cotinus coggygria among those plants which respond well to this pruning technique.

Season All Season
Date 2006-12-08
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Keywords: Callicarpa

PAL Question:

I have a Callicarpa with light green leaves and very small purple berries in the winter. I don't know what the one I have is called, but I would like to find one with dark green leaves and dark purple berries. How late in the season could I put a shrub like this in my yard in South Seattle?

View Answer:

Sometimes having two Callicarpa plants in one garden will enhance berry production. The variety that reportedly does best in the Pacific Northwest is Callicarpa bodinieri var. giraldii 'Profusion.'

I wonder if the variety you currently have might be this one, Callicarpa dichotoma 'Early Amethyst,' which has paler purple berries that are fairly small.

I'd never heard of the cultivar 'Purple Pearls' before, but it appears to have darker (purple-tinged!) leaves and richly purple-colored fruit.

Portland-area gardener and author Ketzel Levine writes about several types of Callicarpa in Plant This! (Sasquatch Books, 2000). She says that Callicarpa bodinieri var. giraldii 'Profusion' is the only type of Callicarpa "that truly thrives in temperate climates" (such as ours). "For reasons [...] no doubt related to the weather, and the absence of a long season of heat---none of the other species berry up quite as reliably." She does say that Callicarpa americana's berries are three times larger than 'Profusion' and that Callicarpa dichotoma is a more graceful plant ("the most refined and shapeliest species in the genus. It has a horizontal, tiered habit," but its berries are smaller. Callicarpa japonica has "metallic purple fruits, a color just a tad weirder than most, set off dramatically by autumn leaves often touched with pink." There is a white-berried form of Callicarpa japonica--'Leucocarpa.'

However, all of the other varieties (aside from 'Profusion') may not perform well in the Pacific Northwest.

You can plant more Callicarpa plants as you find them in nurseries or at plant sales. To be on the safe side, don't plant in summer heat or you will have to pay very close attention to watering, and don't plant when the ground is frozen or saturated. Spring or fall planting will work just fine.

Season All Season
Date 2014-03-15
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Keywords: Vitis, Pruning

PAL Question:

I have a grapevine that is totally out of control and growing from the arbor into the trees. How and when should it be pruned back? I cut one vine that was up in the tree and it seemed to "bleed water."

View Answer:

From the American Horticultural Society Pruning and Training Manual, ed. by C. Brickell (1996, p. 289.):
"Prune only in midwinter when the risk of sap bleeding from cuts is at a minimum; any later, and bleeding may be difficult to stop (cauterization with a red-hot poker is the traditional remedy)."

From the book The Grape Grower, by L. Rombough (2002, p. 44-45.):
"Pruning Neglected or Overgrown Vines...If the trunk of the vine is straight, or is otherwise healthy, you may be able to short-cut the process by cutting everything back to the head of the trunk. You will have no crop that season, but you can easily train the new shoots that emerge as canes or new cordons to bear a full crop the following year.
More often, the vine will be such a mess of old growth and oversized wood combined with twisted, multiple trunks that the simplest way to prune it is with one quick cut, through the base of the trunk(s), right at ground level.
Kill the vine? No! Almost without fail, the vine will bounce back and refill the arbor or trellis in one season, because it has the full vigor of a large, established root system behind the new growth. The newly regrown vine should resume full production the very next year."

Season All Season
Date 2006-06-16
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Keywords: Vitis

PAL Question:

What grapes for eating ripen in the Seattle area? I do grow concord, but are there any red or green grapes that ripen in this climate?

View Answer:

Both WSU and OSU Fruit Research Stations recommend Buffalo, Canadice, Van Buren, Vanessa and Venus. Following is WSU's entire list:

  • Table grape varieties (*currently planted at Mount Vernon)
  • Buffalo - midseason Concord type, blue
  • Canadice* - early pinkish red
  • Interlaken Seedless* - early white, vigorous
  • Lynden Blue - very early blue, seeded
  • Mars* - medium early, blue
  • Reliance*- early, red, table and juice
  • Saturn* - medium early, red
  • Van Buren - blue Concord type, early
  • Vanessa* - early red
  • Venus* - early red
  • NY 78.836.06* - selection from Geneva, NY breeding program
(Source: Washington State University, Mount Vernon)

You may find Oregon State University's publication about Growing Table Grapes by Bernadine C. Strik of interest as well.

Season All Season
Date 2008-01-24
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Keywords: Quirky, Hummingbirds, Animal-plant relationships, Pollinators

PAL Question:

I would like to know how the hummingbird's feeding affects the level of nectar in flowers. I already know about which flowers produce nectar that will attract hummingbirds. My main concern is whether hummingbirds can use up a plant's supply of nectar.

View Answer:

There has been some research which suggests that a plant's production of nectar is regulated by hormones. Sometimes the hormone attracts one creature in order to repel another. The article excerpted below suggests that rapeseed plants produce nectar to attract ants that will defend them against caterpillars. Source: Max Planck Society for the Advancement of Science (March 29,2010):
"Jasmonic acid and related molecules are constituents of molecular signal transduction chains in plant tissues. These compounds - generally referred to as jasmonates - are synthesized when caterpillars feed on plants; they are signalling substances and belong to the group of plant hormones. By producing jasmonates the plant regulates its defence against herbivores e.g. by stimulating the synthesis of toxins. Moreover, previous studies have shown that jasmonates regulate the production of "extrafloral nectar". This particular nectar, which is produced by special glands called "extrafloral nectaries", has nothing to do with pollination, but attracts ants to the herbivore-attacked plants as defenders against their pests. The sugars in the nectar reward the ants for defending the plant. The same principle applies to floral nectar: nectar production in the flowers attracts and rewards pollinators which in turn contribute substantially to the seed yield. However, up to now, it has not been clear how nectar production is regulated in the flowers."

In the book The Biology of Nectaries edited by Barbara Bentley and Thomas Elias (Columbia University Press, 1983), there is an essay called "Patterns of nectar production and plant-pollinator co-evolution" (by Robert William Cruden et al.) which states that "flowers pollinated by high-energy requiring animals [this would include hummingbirds] produce significantly more nectar than flowers pollinated by low-energy requiring animals, such as butterflies, bees, and flies."

Similarly, plants whose pollinators are active in the day produce more nectar during the day, and plants pollinated by nocturnal creatures will make more nectar at night. So clearly there is an intricate system of response between the needs of the plants and the needs of the hummingbirds, and the biology of individual plants has evolved to serve the plants' interests which are tied to those of pollinators. In effect, the hummingbird can't exhaust the nectar supply of the flowers, because the plant has adapted to meet its needs.

Season All Season
Date 2010-08-25
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Keywords: Cornus florida, Cornus nuttallii, Cornus

PAL Question:

I have a 22-year-old Eddie's White Wonder Dogwood. It bloomed the first three springs after planting and then stopped blooming until this spring.

It is planted at the edge of a woodland, facing south. It received summer water the first few years, but not since then, because Sunset Western Garden Book advised re: Cornus nuttallii, part of Eddie's cross: "Give infrequent summer water."

I did water it more last summer, as it was so hot and dry in our area. And it finally bloomed!

My question--Do you think that the bloom this spring was the result of more water during the summer, or did the tree have to reach a certain age to start blooming each spring?

View Answer:

There are several reasons that Dogwoods fail to flower. Flowering dogwood does need regular water, according to Sunset's 2001 edition. Other possibilities might be the age of the tree, and extreme temperatures, such as cold, which may kill the buds.

I would suggest continuing to water and see if it flowers again next season.

There is some discussion about dogwoods failing to flower on the forum of University of British Columbia Botanical Garden. Possible reasons include the age of the tree (not applicable in your case), excessive use of fertilizer, cold damage to buds, lack of sun, and more.

The book 1000 Gardening Questions & Answers (The New York Times) has a section entitled, "Why Won't It Bloom." Reasons that dogwood may not flower are similar to those described above:

    1. Overfertilizing - creates excessive foliage
    2. Excessive Shade - need at least 4 to 5 hours a day and more sun means more flowers
    3. Frosts or droughts - at the wrong time (Dogwoods need lots of moisture and we have had several years of drought)
    4. Pruning - removing the flower buds unintentionally

Season All Season
Date 2008-01-24
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Keywords: Pruning shrubs, Hibiscus

PAL Question:

How do we prune a Hibiscus tree that is about 3 feet tall? The plants are located in a container outside of our senior center. They wintered inside and are now too bushy at the top. How do we prune so they are more compact? What is the correct way to care for these wonderful flowering trees?

View Answer:

It sounds like you have Hibiscus rosa-sinensis---the tropical evergreen shrub. Late spring is the time to prune. According to the American Horticultural Society Pruning & Training book: Prune established plants by cutting back main shoots by as much as one-third, and shorten laterals, leaving two or three buds. Dead wood attracts canker, so it should be removed promptly. To renovate completely, remove older branches entirely and cut the remainder back hard. The response is usually good, but if most stems have died back, it is best to replace the plant.
(Source: American Horticultural Society Pruning & Training, ed. by C. Brickell, 1996, p. 201).

Other pruning information is available from Hidden Valley Hibiscus.

Also, my personal experience with a 10-year-old Hibiscus is that pinching out tips of stems in spring and summer increases flower production.

Season Spring
Date 2008-01-24
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Keywords: Vaccinium parvifolium, Shepherdia canadensis, Sambucus cerulea, Rubus leucodermis, Rosa gymnocarpa, Amelanchier alnifolia, Rosa nutkana, Oemleria cerasiformis, Berberis nervosa, Berberis aquifolium, Malus fusca, Prunus virginiana demissa, Prunus emarginata, Quercus garryana, Corylus cornuta, Crataegus douglasii, Rhamnus purshiana, Vaccinium ovatum, Vaccinium ovatum, Umbellularia californica, Rubus spectabilis, Gardening to attract birds, Attracting wildlife, Rosaceae (Rose Family), Gaultheria shallon

PAL Question:

I am planning a garden in Seattle and my highest priority is to attract birds. Do you have a list of plants I can use as a reference?

View Answer:

This is a more difficult question than one might imagine. According to Landscaping for Wildlife in the Pacific Northwest, "almost 300 species of birds are native to the Pacific Northwest. Many of them could call your yard home for at least part of the year, depending on what you provide for them. So it depends on what species of birds you want to attract and what environments they need."
Source: Landscaping for Wildlife in the Pacific Northwest, by Russell Link (University of Washington Press, 1999, p. 48).
There is a lot of good advice on planning your garden with birds (and other creatures) in mind.

Washington Native Plant Society has a resource page devoted to native plants for wildlife.

The Miller Library has a booklist featuring titles on attracting wildlife to the garden: Information Resources for Gardening with Wildlife.

Another good source for this information is Native Plants of the Northwest, by Wallace W. Hansen. Scroll down to Wallys Wildlife Habitat Recommendations.
Following is an annotated list of plants that attract birds for western Washington: the oaks, chinquapin, Oregon myrtle, western hazelnut, cascara, and all trees in the Rose family (hawthorn, bitter cherry, chokecherry and Pacific crabapple). Native shrubs include: serviceberry, salal, all Oregon grapes, Indian plum, bittercherry, roses, blackcap, thimbleberry, salmonberry, Pacific blackberry, red and blue elderberries, russet buffaloberry, mountain ash, snowberry, and all huckleberries.

Seattle Audubon's book and online resource, Audubon at Home in Seattle: Gardening for Life has a chapter on designing a garden to attract birds, and it includes a plant list.

Season All Season
Date 2008-01-24
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Keywords: Quercus, Phytophthora, Nuts

PAL Question:

I have a few acres in South Kitsap where I am creating pasture by cutting down many of our firs and pines. We will have herds of goats and sheep and swine. I like the idea of acorns for swine and the increased btu of oak for firewood. From my research, it seems that Garry oak and White oak grow too slowly, while Red oak and Pin oak are fast and produce a lot of acorns.

So, I'm leaning towards Red and Pin Oaks, particularly Pin Oaks, but is the fact that these aren't native a problem? Would these trees grow well in the Pacific Northwest, in sandy loam with low nitrogen a pH of 5.3. The soil has pretty good organic matter, Potassium and Magnesium. The trees will be planted in a full sun to mostly sunny area, but depending on the angle of the sun, the surrounding firs throw a pretty big shadow.

Are there other oaks with good acorns I should consider?

Also, is Sudden Oak Death a problem in the Puget Sound?

View Answer:

I'll start with your last question first. Washington State University has a Sudden Oak Death information page. A summary of the work researchers are doing may be found in a 2013 edition of WSU's online newsletter, On Solid Ground.

I have certainly heard that it is present in our region. If you are concerned, you may want to purchase from nurseries with certifications from the USDA Plant Health Inspection Service saying that they are free of the disease. Here is a list of nurseries that have such a certificate. Interestingly, the plants on which Phytophthora ramorum has been detected (in nurseries) in our state are not oaks, but Rhododendron, Viburnum, Camellia, Kalmia, and Pieris. Outside of nurseries, the pathogen has only been found on salal.

The USDA Plant Health Inspection Service has a list of other plants which are hosts of SOD.

Returning to your questions about species of oak, Oregon State University's Landscape Plants Database has information about Quercus rubra (Red oak)and Quercus palustris which confirm that they prefer sunny sites. Red oak will produce acorns in two years. Pin oak is one of the fastest growing oaks, and its acorns (also produced after 2 years) are small.

Local tree expert Arthur Lee Jacobson has this to say about Quercus rubra in his Trees of Seattle (2006):

"New Jersey's State Tree proves to be Seattle's fastest-growing oak, on average. [...] the safest bet if you want an oak in a hurry is to plant a Red oak--and then stand back!" Here is what he says about pin oak, Quercus palustris: "Seattle's most abundant oak. [...] Pin oak is slender in all respects: trunk, limb, branch, twig, leaf--only the tiny squat acorns belie the name. Rapidly growing, it can attain up to 135' x 23 1/4". Inexperienced tree-watchers must be careful not to confuse it with Scarlet oak, which is less common, less slender, makes bigger acorns [...]."

The only aspect of your site description that concerns me, as far as these two oak choices, is the sun exposure--you might want to see how far the shadow of the firs extend, as these oaks will do best in sun. Unless your goal is to plant native species only, I do not see a problem with adding these non-natives to your landscape. You can certainly add lots of native shrubs and perennials if you feel that would be advantageous. There are some excellent resources for selecting native plants:
Washington Native Plant Society's landscaping guides
King County's interactive Native Plant Guide

As far as other good acorn-producing oaks which are also large trees, I can see that Arthur Lee Jacobson mentions English oak (Quercus robur) for its large acorns--and this is also potentially a very large tree (150' x 40+'). Scarlet oak (Quercus coccinea) has notably large acorns too. Burr oak (Quercus macrocarpa) has the largest acorns, but does not do very well in our area. The native Garry oak (too slow a grower for your needs) Quercus garryana does produce acorns.

If you want to diversify the source of nuts (in case of Sudden Oak Death), you might want to consider adding some hazels and filberts (Corylus species) which should do well here. (I don't know if pigs and goats will eat these, though.)

Season All Season
Date 2011-11-05
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Keywords: Raised bed gardening, Soil testing

PAL Question:

I recently moved to a new house that had what looked like a fair amount of chemicals dumped on the land around it. What do you recommend as a base soil for raised beds for organic gardening if you do not want to trust what you have?

View Answer:

The first thing you might consider doing is having your soil tested. There are various labs that can test for toxins as well as for soil type and nutrient deficits. Here is a link to a WSU site, which lists the labs and what they do. These labs primarily serve agriculture, so you might consider getting a soil test from a lab that specializes in home gardens, such as University of Massachusetts, Amherst. Also, if you suspect heavy metals in the soil, there is a link from Seattle-King County Public Health to labs that will test for toxins.

In her book, Backyard Bounty (New Society Publishers, 2011), British Columbia gardening expert Linda Gilkeson says that for your raised bed (or any situation where there was either no native soil, or where you are replacing the existing soil) you should "buy the best soil available, and mix in a generous amount of compost, leaf mold (well-rotted leaves) and other organic matter as you fill (1 or 2 parts compost to 9 parts soil)."

If you purchase topsoil, make sure to find out what the composition of the topsoil is. Linda Chalker-Scott's factsheet from Washington State University Extension indicates that the ideal percentage of organic matter [abbreviated as OM] in topsoil used for gardens is 5% by weight.
Excerpt from the WSU blog discussion of this topic:
"If you're purchasing topsoil, check out what you will be getting before it's delivered. Ask the seller what the topsoil contains and also ask for the producer's test data regarding pH, salt level, nutrient levels, OM content, and texture. If they don't have that data available, you may want to consider taking a sample and have it tested yourself. Also, find out if the soil has been screened to remove rocks. Before you're stuck with unsuitable topsoil, know exactly what you're getting.
Garden Hint: Topsoil is usually sold by the cubic yard. One cubic yard of soil will cover about 50 square feet to a depth of four to six inches."

Season All Season
Date 2008-01-31
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Keywords: Shade-tolerant plants, Gardening in the shade

PAL Question:

Which flowers can be planted in the shade?

View Answer:

The University of Minnesota Extension Service article entitled, "Gardening in the Shade" provides lists of annuals, perennials and herbs that do well in the shade.

Gardening with Ed Hume offers advice about growing plants in shady areas under tall trees.

For resources specific to the Pacific Northwest, try the list of shade perennials from Paghat's Garden, Great Plant Picks, King County's searchable Native Plant Guide, and lists of native plants for mostly to fully shady sites Washington Native Plant Society. There are also numerous books available in the Miller Library. Here is a booklist.

Season All Season
Date 2008-01-31
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Keywords: Trachystemon orientalis, Invasive plants, Ground cover plants

PAL Question:

A mail-order nursery catalog I recently browsed is touting Trachystemon orientalis as the plant for problem areas of the garden where other plants would struggle. They say it will rapidly cover blank or weedy areas in the garden, whether they are sunny, shady, wet, or dry. What can you tell me about it? It sounds intriguing, but I'm worried it might be invasive!

View Answer:

Trachystemon orientalis is in the same family as borage (Boraginaceae), with similar blue flowers and rough leaves (to my eye, it's a plant for a wild garden, with its resemblance to borage and comfrey). According to Perennials by Roger Phillips and Martyn Rix (Firefly Books, 2002), it is a native of eastern Bulgaria, northern Turkey, and the western Caucasus region. It is naturalized in parts of England. The authors say it thrives "in wet beech forest on shady river banks and on damp rocks at up to 1000 meters, flowering in March-May." It spreads by rhizomes and is tolerant of neglect. Its preferred site is moist shade, but it adapts to a wide variety of conditions, and excels at smothering weeds. There is additional information from Missouri Botanical Garden.

You may be right to wonder when a plant seems to be just the thing for almost any spot, and when it is promoted for its ability to spread easily. Some ground cover plants hover on the brink between covering the ground you want covered, and exceeding those boundaries. Trachystemon's common name is Abraham-Isaac-Jacob. The origin of that name is unclear, but my interpretation is that a plant named for the patriarchs of Genesis has a connection to generational continuity, a fitting name for a plant which is skilled at self-propagation!

See garden writer Margaret Roach's blog post entitled "A Plant I'd Order," and notice what she says about the likely behavior of this plant in the Pacific Northwest.

Trachystemon orientalis is included in the Manual of the Alien Plants of Belgium and is listed in the Invasive Species Compendium. You could test its behavior in your garden for a season or two, and if it shows signs of aggression, you should still be able to eradicate it. If your aim is to be cautious, you may want to avoid planting it.

Season All Season
Date 2015-01-24
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Keywords: Native plants--Washington, Ground cover plants

PAL Question:

I am looking for a native groundcover to grow as a walkway along side my house. It is a shady spot and it would need to be a hardy plant that could be walked on.

View Answer:

Regrettably, there are not any native, shade-loving, walkable ground covers available unless you are interested in mosses. If that is appealing, you can check in the book Plants of the Pacific Northwest Coast by J. Pojar. The following websites may help you find native plants:
King Conservation District
King County Native Plant Guide
Washington Native Plant Society

For information on growing mosses, see "Encouraging Mosses" from Oregon State University, based on the writing of George Schenk.

If your heart isn't definitely set on natives, there are some good alternatives:

  1. In her book Big Ideas for Northwest Small Gardens, Marty Wingate recommends Mazus reptans. It is semi-evergreen to evergreen with tiny blue flowers from late spring through summer. It takes full sun to part shade and is delicate looking, but takes foot traffic. It requires some fertilizer to stay perky. (Note: I use it in my garden--it is versatile and pretty)
  2. Another source of ideas is the website http://stepables.com/
    Click on plant info, then plant search.
  3. A ground cover that I have found useful (it can take car traffic a couple times a day) is Leptinella gruveri Miniature. You're almost certain to find it at the website above.

Season All Season
Date 2008-01-31
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Keywords: Campsis, Woody plant cuttings, Woody plant propagation

PAL Question:

I have a trumpet vine. I needed to move it, and during the relocating, I also cut its woody upright trunk about 3 feet up, and it was about 6 feet -- the woody part. It had a lot of leaves, or branching growth. I wonder what would I have to do to start a new plant from this part I've cut off?

View Answer:

The best way to propagate the top part of your vine Campsis radicans) is with semi-ripe or hardwood cuttings. North Carolina State University Extension has good general information on propagation. The Royal Horticultural Society's page about Campsis includes information on various propagation methods.

Season All Season
Date 2008-01-31
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Keywords: Rooting, Yucca, Propagation, Transplanting

PAL Question:

I have a number of large Yucca plants in my yard that I would like to dig up and transplant. I am not entirely familiar with this type of plant, but have noticed that, likely due to the age of these plants, several trunks have sprouted from the mother plant and have begun growing as what appear to be separate plants. However, these extensions are easily lifted from the ground and show no evidence of independent root development. Can I cut the new plants from the original plant and get these to take root elsewhere?

View Answer:

Following is some information that may help you in transplanting your Yuccas.

TRANSPLANTING

From Agaves, Yuccas and Related Plants: A Gardener's Guide by Mary & Gary Irish (2000, pages 65-68)

    In mild winter climates that have hot summers, particularly hot and dry summers, fall planting is best, so that root systems establish through the mild winter before the onset of the stressful summer season. If planted in early spring, plants must be carefully watered and shaded from the sun during the summer to prevent sunburn and debilitating heat stress. When planting agaves [& yuccas], regardless of the soil type, raise the center of the hole slightly, just an inch or so, and plant the center of the plant at the top. The crown of the agave [or yucca] particularly is susceptible to infections, and when the soil inevitably subsides after planting, the crown can sink below the soil line. The practice of raising the center of the planting hole slightly is helpful in all the stemless members of both families to prevent crown rots.

    For all plants, begin by digging a shallow hole no more than the depth of the root system.Backfill the planting hole without soil amendments or with a very small amount of compost. Tamp the soil lightly as it is backfilled to prevent excessive settling later...

    Moving mature arborescent plants, such as some members of Beaucanea, Furcraea, Nolina or Yucca, is more difficult. These large plants are sensitive to root and stem disturbance, and wounds of the basal growing platform in Yucca can introduce a host of infectious agents into the plant. If possible, it is much more advisable to move such plants when they are young and nearly stemless.

PLANTING TOES & SUCKERS

From American Horticultural Society Plant Propagation by Alan Toogood (1999, p. 145)

    TOES

    Uncover the roots of a mature plant. Remove swollen buds (toes) from the parent rhizome, cutting strain across the base of the toe. Pot each toe singly in a free-draining medium, at twice its depth. Water. With bottom heat (59-68 F) the toe will root in 2-3 weeks.

    SUCKERS

    In spring, carefully uncover the base of a sucker. Cut it off at the base where it joins the parent rhizome. Dust the wounds with fungicide. Pot the sucker singly in a free-draining medium, such as equal parts soilless potting mix and fine grit. Keep at 70 degrees F until rooted (12 weeks).

Season All Season
Date 2007-04-20
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Keywords: Gerbera

PAL Question:

My Gerbera daisies look marvelous, however, the flowers come up only a few inches and then wilt and fall over, but the leaves look great. There are no yellow leaves to denote over watering. What am I doing wrong? They are planted in the ground.

View Answer:

Ideal growing conditions for Gerberas include the following:

SOIL: A medium that has adequate pore space and yet retains substantial amounts of water should be used. Peat moss and peat-like substances, therefore, are essential ingredients in the preparation of media... The soil pH should be adjusted to between 5.5 to 6.2 for optimal gerbera growing conditions. In very acid soils this can be achieved by adding either limestone or dolomite to the soil mix.It would be hard to get too much organic matter into the soil for this plant. A mixture of one-third sand, one-third leaf mold and peat moss, and one-third rich loam...is ideal.

WATER: Moist well-drained... Gerberas require an abundant supply of moisture, but will succumb under waterlogged conditions.Best grown in areas of long, warm summers and high humidity.

FERTILIZATION: Fertilize lightly but regularly... Fertilizers containing a high percentage of an ammonia-type nitrogen should be avoided.

LIGHT: ...Provide protection from the afternoon sun in hot climates (i.e. summer in the Pacific Northwest).

PLANTING: The most important factor in gerbera production is transplanting... Gerberas need to be transplanted with the crown at or preferably above soil level. The crown should be visible at all times, and should be allowed to dry out between irrigations.

If you are doing all of this and the flowers are still drooping, you might want to dig one of the plants up and take it to a Master Gardener clinic. If they do not know what is wrong, ask them to send it to the pathology laboratory in Puyallup. It is better to go through Master Gardeners first so you will not be charged. To locate your nearest clinic, go to http://mastergardener.wsu.edu and click on I Want to Talk to a Master Gardener Volunteer.

Sources:
1. Annuals for Every Purpose, by L. Hodgson, 2002, p. 138-139.
2. International Plant Propagators' Combined Proceedings, vol. 34, 1984, Gerbera Production and its Problems, by B. Tjia, p. 365-381.
3. American Horticultural Society Illustrated Encyclopedia of Gardening; Annuals, ed. by M. Yee, 1982, p. 101-102.
4. Annuals and Perennials, by editors of Sunset Books, 1993, p. 72.

Season All Season
Date 2008-01-31
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Keywords: Pollination, Actinidia

PAL Question:

I have two very healthy Kiwi vines, one male and one female. My female plant is flowering profusely right now, but there are no flowers on the male plant. I have had the plants for about 15 years or more and have never had fruit. They do not seem to bloom at the same time. I have just never bothered about it before, but this year I thought I would check out some options.

Any resources regarding hand pollination (both instructions and local suppliers) would be really helpful.

View Answer:

Oregon State University Extension's guide, Growing Kiwifruit by Bernadine Strik (2005), has information about pollination:
"For fruit to be produced, male and female vines must be present in a block and must flower at the same time. Male flowers produce viable pollen for only the first 2 to 3 days after opening. However, female flowers are receptive to pollen for 7 to 9 days after opening, even when the petals have started falling.
"Pollination is extremely important in kiwifruit production. Large fruit contain 1,000 to 1,400 seeds (research on Hayward). If pollination is poor, fruit will have indentations (narrow valleys) on one side or be non-uniform in shape. If you cut through these fruit, you will find no seeds in these areas.
"Kiwifruit flowers are pollinated mainly by insects, although wind may play a minor role. Honey bees are the main pollinator used in kiwifruit vineyards. Kiwifruit flowers do not produce nectar and are relatively unattractive to bees. About three to four hives per acre are needed to adequately pollinate kiwifruit. Place these in the vineyard no sooner than 10 percent bloom of the female vines.
"In some years, you may have no male vines in flower as a result of winter injury to male plants (they are less hardy than the females). In this case, no naturally produced pollen will be available. To get a crop, the females will have to be pollinated artificially. Call your county Extension agent for more information on sources of pollen and methods of artificial pollination."
(Note the section on Hardy Kiwi which are different than Fuzzy Kiwi.)

You might also find this article from The Olympian newspaper (May 16, 2009) of interest. It features kiwi growers Hildegard Hendrickson and 'KiwiBob' Glanzman, and discusses hand pollination, general care, pruning and training.

Season All Season
Date 2008-01-31
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Keywords: Agapanthus

PAL Question:

The Agapanthus in my greenhouse are budding. I would rather not have them bloom now. Can I set them outside to slow them down or would that do more harm than good?

View Answer:

If your Agapanthus has set buds and is beginning to flower, there is not much you can do to slow it down. Putting it outside will not harm it when the danger of frost is past.

Season All Season
Date 2006-07-07
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Keywords: Rhododendrons--Washington, Rhododendron

PAL Question:

My two rhododendrons did not produce any blooms this year- they are healthy otherwise. Why?

View Answer:

I had the same problem with one of my rhodies this spring (all the others were fine), as did many other people in the Pacific Northwest. Following are the most likely causes:

NO FLOWERS, BUDS DO NOT OPEN. This is most likely to be caused by frost, either in mid-winter by the hardest frosts of the year, or in spring when the buds are swelling and about to open. Certain varieties have very frost-vulnerable swelling buds, while many species have buds which are easily destroyed even by quite mild winter frosts.

NO FLOWERS, NO FLOWER BUDS. There are several possibilities why rhododendrons may not flower freely:

  • Too much shade. This is very common in North America where, in order to regulate sun and soil temperature, plants are placed in deep shade. This allows healthy, if straggly growth, but can inhibit flowering. The more light you can give a plant, the more likely it is to flower, so there is a trade-off between the need for shade and the need for light.
  • The variety takes many years to flower (it does not sound like this is your situation).
  • Kindness. Rhododendrons flower in order to reproduce. A contented, well-fed, well-watered well-shaded plant may not feel any need to reproduce, as it perceives no threat to its survival. Do not feed after mid-summer, as this encourages growth at the expense of flowers. Nurserymen cut down watering in late summer to stress plants into flowering the following year.

(Source: Rhododendrons: A Care Manual, by K. Cox, 1998, p. 73).

The above is corroborated in other sources, e.g. Success with Rhododendrons and Azaleas, by H.E. Reiley, 1992, p. 132-133.

Season All Season
Date 2007-05-21
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Keywords: Prunus, Fruit--Diseases and pests

PAL Question:

I have a flowering purple plum tree. For the last two years it has had black knobby growths on the limbs. The number of these growths are increasing and there is no sign of any type of bug involved. The tree is healthy in all other respects and the growths remain on the limbs all year. I cannot find anyone who knows what these are and if I need to do anything to stop and/or remove these growths. Obviously they are ugly but probably not fatal and do not spread to any other trees. Can you give me a clue?

View Answer:

We can only guess from your description, and in order to get an accurate diagnosis you will need to take a sample (including both healthy and affected parts if possible) to a Master Gardener clinic. Click on the appropriate link for your local clinic through Master Gardeners / Washington State University Extension.

Meanwhile, for information about common diseases of plums in the Pacific Northwest, try searching Washington State University's HortSense website.
The symptoms you describe are similar to 1. Crown gall, 2. Black canker and 3. Black knot. Click on those diseases for descriptions, photos, and control methods.

You can also take a look at pages like this one, on black knot of ornamental cherry and plum, from Morton Arboretum. See if the images resemble what you are seeing on your tree.

Season All Season
Date 2006-12-08
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Keywords: Container gardening, Bamboo

PAL Question:

I am new to the area, and am renting a house that has 3 containers of bamboo plants on the deck. Two of them appear to be dead or dying, although there is still green in the canes. I tried watering them a lot for a week or so, and for one day they seemed to like that, but then they did not any more, and looked worse. Some theories people have offered: the soil is depleted, they need to be thinned, they have been poisoned somehow. Any advice? Or should I just get new ones? And, where would I get new ones?

View Answer:

Bamboo can grow well in containers, but it can also be picky about drainage, fertilizer and container depth.

Here is an American Bamboo Society article entitled Planting and Caring for Bamboo.

Your bamboo may have a pest or an infestation of some kind. To be sure, you may want to bag a sample of the leaves and take them to a Cooperative Extension Master Gardener Plant Clinic. Master Gardeners are trained in the identification of plants and pests and a host of other botanical subjects. To find out where to purchase bamboo locally, try Bamboo Web's sources search tool.

Season All Season
Date 2006-12-08
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Keywords: Vines--Care and maintenance, Vitis, Viticulture

PAL Question:

I have purchased 150 grape vine, bare-root plants packed in damp wood shavings, covered by plastic. I have been storing them for about 1 1/2 weeks. A number of circumstances have prevented me from planting them and I am concerned they are going to begin to mold. The current weather forecast suggests I need to do something temporarily with them before permanent planting or I am going to lose, most if not all of them.

Any suggestions?

View Answer:

If at all possible you should place your plants in refrigeration or in the coolest place possible. Store them in the dark, and uncover the plastic. Check frequently to make sure the wood shavings stay barely damp.

Alternatively you can "heel them in" which means unpacking, but leaving the plants in bunches and temporarily "planting" them in either the ground or in large containers of peat moss based potting soil.

Source: Oregon Viticulture, ed. Hellman (2003).

Season All Season
Date 2006-07-14
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Keywords: Soil amendments

PAL Question:

I have very bad rocky, clay soil. To dig in this is like prison work. We rototilled the area and put in topsoil and now it is like quicksand. I am going to build up my beds but want to break some up to get trees and other plants to take root. What are you supposed to use or do with hard clay? I love plants, and would like to get gardening, but I can't think of how to solve this problem.

View Answer:

There is no immediate solution. It may take a few years of adding good amounts of organic matter and compost to improve the soil quality. Here is some information that may help you along the way.

A Seattle Post-Intelligencer article, 'The well-made bed: Pile on the compost' by Ann Lovejoy, provides some tips for improving your soil with compost.

Washington State University Extension horticulture professor Linda Chalker-Scott has a cautionary tale on how NOT to amend clay soil, plus tips on improving it slowly over time.

Fine Gardening has an online article on improving clay soil.

Lastly, a Home and Garden Television article entitled, "How to plant in rocky soil" may help you overcome the rockiness of your yard.

Season All Season
Date 2006-12-08
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Keywords: Insect pests--Control

PAL Question:

Is there really a plant that will ward off mosquitoes, and if so, what is the name and is it available in the Seattle area?

View Answer:

There is disagreement about the extent to which certain plants repel mosquitoes. Below, please find some web sites that highlight some plants that may work.

There are eleven plants generally thought to repel mosquitoes:

Citronella, Eucalyptus, Pennyroyal, Rosemary, Rue, and Wormwood. Milder ones (in our experience) include Basil, Bay, Lavender, Sage and Thyme. With even the smallest of herb gardens, or access to a supermarket selling freshly-cut herbs, the leaves of such plants can simply be rubbed on pets and people to temporarily ward off insect attacks.
(Source: Janette Grainger & Connie Moore. Natural Insect Repellents for Pets, People & Plants. 1991, p.11.)

According to Donald Lewis of the Department of Entomology at Iowa State University, citrosa, lemon thyme or citronella grass may help repel mosquitoes, but you have to crush the leaves and rub them on your skin to make them work.

According to the MadSci Network, citronella oil may be more effective at repelling mosquitoes than the plant itself.

Lastly, the Colorado State Cooperative Extension recommends scented geranium, lemon grass and a host of other plants.

There are many local nurseries which may carry the plants mentioned above, but since inventory changes frequently and they do not list their inventory online, it is best to give them a call to find out if plants you are seeking are available.

Because of the ongoing concern about West Nile Virus, there is a lot of information available on ways to control mosquitoes. See King County Public Health's resources on this topic.

Season All Season
Date 2008-01-31
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Keywords: Abies, Edible wild plants, Pseudotsuga menziesii, Ethnobotany

PAL Question:

There seems to be a new fad of local foragers making tea from the needles of Douglas fir and Grand fir. I am guessing there are Native American origins to this practice. How safe is it, especially in an urban environment? Are there supposed to be benefits to drinking this kind of infusion?

View Answer:

There is a deep tradition of ethnobotanical uses of various parts of both Douglas fir (Pseudotsuga menziesii) and Grand fir (Abies grandis). Nancy Turner's book, Thompson Ethnobotany: Knowledge and Usage of Plants by the Thompson Indians of British Columbia (Royal British Columbia Museum, 1990) says that "a beverage tea was made by boiling Douglas-fir twigs with their needles. This tea was said to have tonic and diuretic properties."

Turner says there is a great deal of confusion surrounding both the English common names and Thompson Indian names for various fir species. This makes it difficult to know which species were intended for which uses. An infusion made from the boughs of a species that might be Grand fir (Abies grandis) "could be drunk for any illness." In Ethnobotany of Western Washington (University of Washington Press, 1973), author Erna Gunther notes both distinctions and confusions between Abies grandis and Pseudotsuga menziesii: according to the Green River informant she consulted, tribe members boiled Grand fir needles as a tea to treat colds, but a Swinomish informant believed Grand fir and Douglas fir to be the same species.

Douglas fir and Grand fir are not mentioned in Toxic Plants of North America (George Burrows and Ronald Tyrl, Wiley-Blackwell, 2013), but a plant's absence from a list of toxic plants does not mean that it is risk-free. Common sense says it would be best not to gather needles from urban trees that are not your own, since there is no way of knowing whether those trees might have been sprayed with pesticides, or exposed to air pollutants.

According to Stephen Facciola's Cornucopia II: A Source Book of Edible Plants (Kampong Publications, 1998), tea made from young foliage and twigs of Pseudotsuga menziesii is both refreshing and high in vitamin C. He says that the young branch tips of various species of Abies, including A. grandis, are used as a tea substitute.

I could not find reliable information about the recommended quantities of needles to water, ideal length of boiling time, or chemical properties of needles used for tea. Elise Krohn, author of Wild Rose and Western Red Cedar: The Gifts of the Northwest Plants (self-published in 2007) has information on her Wild Foods and Medicines blog about "making evergreen tree tip tea." My advice would be to proceed with caution and consult a medical professional in case a coniferous tisane might have potential interactions with other substances. (Even a popular beverage like Earl Grey tea can be problematic due to the Citrus-derived bergamottin which interacts with some medications).

Season All Season
Date 2015-05-16
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Keywords: Rubus discolor, Roadside plants, Weed control--Pacific Northwest

PAL Question:

I live next to a Washington Department of Transportation I-5 easement land where the department has let blackberries run rampant. As a result, I have thousands of blackberry seedlings in two areas of my property at this time of year. Is there any effective way to kill them at this stage?

View Answer:

In King County, Himalayan blackberry is a Class C noxious weed, meaning that control is not required by law, but is recommended in natural areas and restoration sites.

University of California, Davis Integrated Pest Management describes various methods of controlling blackberry.

In Ann Lovejoy's Seattle P-I article dated, Thursday, June 7, 2001, she describes vinegar-based herbicide as a means of controlling weedy blackberries and horsetail.

You may also want to contact WSDOT's roadside vegetation maintenance department to report the problem with unwanted blackberries migrating onto your property.

Another option, increasingly being used for large areas with invasive weeds, is to rent goats, who will eat the weeds down to the ground. The Seattle Post-Intelligencer published an article on this subject in 2007. "Rent-a-Ruminant" on Vashon Island is one example of a goat rental service.

Season All Season
Date 2008-01-31
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Keywords: Failure to flower, Frost, Rhododendron, Master gardeners

PAL Question:

This is the second year in a row that my rhododendron Blue Peter has flower buds but they are dry and somewhat dark and have no flowers at all. These buds are easy to deadhead. Can you help me salvage this rhododendron, which is very old, and beautiful when it blooms?

View Answer:

In order to get an accurate diagnosis you will need to take a sample of your plant (including both healthy and affected parts if possible) to a Master Gardener clinic. If they do not know what it is, ask them to send the sample to the pathology laboratory in Puyallup. It is best to go through Master Gardeners first so you will not be charged. If you send the sample yourself there will be a fee.

Meanwhile, several sources mention frost, drought, and "bud-blast" (unlikely in the Pacific Northwest) as potential causes of bud failure. Damaged flower buds and poor bud set: It is always most disappointing when fat, healthy looking flower buds either fail to open at all or only open a percentage of their buds, the rest being black and dead. Some rhododendrons regularly abort some or even all of their buds for no apparent reason. This may be due in some cases to a deficiency, perhaps magnesium, or to drought reports from various places give mixed results from applying magnesium (usually as Epsom salts)... By far the most usual cause of bud damage is frost. Flower buds are invariably less hardy than the rest of the plant so a really hard winter is sure to cause losses to flower buds. Early autumn frosts can damage buds that are not fully hardened off. This is a very annoying type of damage that may be overlooked and may not be noticed until the buds attempt to open in spring. Rhododendrons vary greatly in their ability to harden up enough to withstand early frost. In areas very prone to spring frosts, it is better to avoid growing plants that always burst into growth at the first sign of spring. Plants that frequently loose their first growth flush (and sometimes even their second) are liable to become stunted and rarely flower.

Source: The Cultivation of Rhododendrons, by P. Cox, 1993, p. 244.

Season Spring
Date 2006-10-26
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Keywords: Plant diseases--Diagnosis, Hydrangea

PAL Question:

Why are the leaves of my oakleaf Hydrangea turning brown around the edges and falling off?

View Answer:

We do not diagnose plant problems, especially without a sample. It might be wise to bring a sample to your local Master Gardener clinic. You can locate a Master Gardener Clinic within Washington State here.

However, based on my personal experience with my own oakleaf Hydrangea (Hydrangea quercifolia), it is a semi-deciduous shrub that will hold on to its leaves through winter, only to replace them with fresh growth in the spring. All my Hydrangea's old leaves have turned reddish-brown and look very ratty. Once new growth resumes in spring, I cut off most of the tattered leaves. (Don't do it too early, in case there is a late frost.)

If you have new growth, do not worry about your shrub, but if you do not have new growth or it is the new growth that is turning brown then you should take a sample leaf into one of the Master Gardener clinics (linked above).

Season All Season
Date 2008-01-31
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Keywords: Prunus laurocerasus, Plant diseases--Diagnosis

PAL Question:

I am losing leaves on my improved English laurel. They turn bright yellow and fall off. I have heard that some loss is normal, but I have one bush losing at least 15 leaves. They have been in the ground now for 4 weeks.

Second question if I could? When a plant turns yellow from the bottom but the top looks normal and wants to bloom what is the problem. Too much water, etc. It just a small flowering plant and the bottom is getting yellow like it is not happy but the top wants to grow fine.

View Answer:

I will take your second question first: When the oldest leaves turn yellow, but the top of the plant still looks fine, that is usually a sympton of nitrogen deficiency. When nitrogen is deficient in the soil, plants will move nitrogen from the oldest leaves to new leaves, resulting in yellowing, or chlorosis, of the oldest leaves. The Sunset Western Garden Problem Solver recommends using a fertilizer containing nitrogen according to directions on the label for the kind of plant you have. You did not mention what kind of plant it is. The fertilizer will give the plant a quick boost. For longer term health, blood meal or fish meal scratched lightly into soil surface around the plant (follow package directions for amount), topped with a one-inch layer of compost will improve the nitrogen content and overall quality of the soil.

(Adding an inch of compost to planting beds in early spring is a good annual practice for replenishing soil nutrients and keeping plants happy.)

You wondered if too much water could be the problem. Overwatering can produce nitrogen deficiencies in the soil by leaching nitrogen down through the soil and away from plant roots. Different plants have different water requirements. Do you know what kind of plant it is? Without knowing what kind of plant it is, and without seeing it, we can only give possible explanations.

Now back to your first question. There are lots of different patterns of yellowing of leaves and each has a different cause. Is it just the bottom, oldest leaves, or newest leaves, or all leaves, or just the edges of leaves, or just between the veins. I would need to know more before even hazarding a guess. But to get an accurate diagnosis for the problems both of your plants are suffering, we recommend you take samples of each, of good leaves and bad and a little bit of soil from around the root zone of each plant to your local Master Gardener Clinic. You can find a Master Gardener Clinic on the King County Master Gardener website.

Season All Season
Date 2008-01-31
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Keywords: Pests, Bamboo

PAL Question:

I have a "fence" of golden bamboo that is approximately 8 years old. It has a black coating on the leaves as well as small white flying insects that scatter when I move the branches. Any ideas as what has invaded my yard?

View Answer:

While we cannot diagnose plant problems remotely, what you describe sounds a bit like aphids or whitefly.

The American Bamboo Society also has information on insect pests that affect bamboo. Here is an excerpt, about aphids:
"Aphids love bamboo! There are over 50 species of Asian aphids known to feed on Asian bamboos. A good example is Astegopteryx bambusifoliae, which sucks sap from the leaves of Bambusa, Phyllostachys, and Dendrocalamus throughout Southeast Asia. It over-winters on the bamboo plant, where it sucks sap from the leaf undersides and culms. It is most common during the winter and spring, and disappears during hot summers. It is controlled by ladybeetles. In general, aphids aren't a major problem since there are so many organisms that prey on them, but they can appear in an occasional outbreak that causes wilting of the leaves and shoots, a reduction in vigor, and stunted growth. They can also transmit fungal diseases, such as black mildew." Bamboo mites are also common in our area.

University of California at Davis "Giant Whitefly" page mentions a black mold that forms during whitefly infestations.

To determine which insect is invading your bamboo, you may want to take a bagged sample to a Master Gardener Clinic for identification. For information about Clinic hours see their website (Plant Clinic Schedule).

Season All Season
Date 2008-01-31
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Keywords: Rhododendrons--Diseases and pests, Rhododendron, Master gardeners

PAL Question:

My rhodies have black spot, rust. Is there a plant medicine I can put in the soil so it will get absorbed by the entire plant rather than spraying every other leaf.

View Answer:

I am sorry to hear about your sick Rhododendrons. You should take a take a leaf sample into a Master Gardener clinic for (free) diagnosis. I have linked a list of clinics in Snohomish County below. Their volunteers are trained in identifying plant diseases and suggesting solutions.

If you cannot get into a clinic try the HortSense webpage from Washington State University Cooperative Extension, and search the common ailments affecting rhododendrons (in the Ornamental Shrubs section).

The reason why it is vital to get an accurate diagnosis is because some fungal diseases do not have treatments that really work, such as rust, while others "leaf spot problems" are not caused by fungus at all, therefore spraying with fungicides or applying a systemic to the soil would only be a waste of time and money!

Try contacting the Snohomish County Master Gardener Clinics to see if you can bring in samples.

Season Summer
Date 2008-01-31
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Keywords: Plant diseases--Diagnosis, Juniperus

PAL Question:

My Sky Rocket junipers are declining. To me it looks like mite damage accompanied by winter damage. The top of the plant is still healthy looking. There are spider mites present. It does not resemble phomopsis, but could be phytophthora. Please let me know what you think.

View Answer:

I checked Diseases of Trees & Shrubs by Sinclair, Lyon and Johnson and Juniper virginiana does not get phytophthora (or at lease this good authority does not list that disease.) It does list a number of other diseases including blight, canker, phomopsis, among many others.

The HortSense website of WSU Cooperative Extension mentions Juniper webworm, which creates heavy webbing, which could resemble mite webbing.

Of course it could be winter damage, like you guess or nitrogen deficiency if the Ph is high (near a lot of concrete?), or salt damage (from melting ice in past winters?).

You should take a sample in to a Master Gardener clinic. If they do not know the cause, you can ask that they "submit it to the diagnostic center at the Center for Urban Horticulture."

Locate a Master Gardener Clinic within King County at this website.

Season Spring
Date 2007-10-11
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Keywords: Cornus florida, Trees--Diseases and pests, Master gardeners

PAL Question:

I have a couple of dogwood trees, both are about 40 years old. In the front yard is a pink dogwood approx 25 ft tall and in the backyard a white one, approx 50 ft tall. Each year in the spring for the past few years the leaves have been browning and falling off the white one. Now the pink one is beginning to develop the same symptoms. Is there anything I can do?

View Answer:

Thank you for your question about Dogwoods. There are several possible causes of leaf drop in Dogwoods. Below, please find referral information for the Master Gardeners and two websites that contain information about pests and diseases of Dogwoods and methods used to control them.

To know for sure what is causing leaf drop in your trees, you may wish to consider bringing a bagged sample of the leaves to the Master Gardeners Diagnostic Clinic here at the Center for Urban Horticulture or another of the many Clinic locations. For Clinic locations and hours in your area, please go to the King County Cooperative Extension website and scroll down to the Seattle Clinics section. Here is the web address: http://king.wsu.edu/gardening/PlantClinics.html.

You mentioned that the leaves of your trees turn brown and then drop. These symptoms are commonly found when Dogwoods have been attacked by Anthracnose. The Washington State University Cooperative Extension's "Dogwood Anthracnose" page may be of use in helping you determine whether your trees have this disease.

Hopefully, this information will get you started. If you would like more information or have any other questions, please be sure and let us know.

I hope that your trees recover!

Season Spring
Date 2008-01-31
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Keywords: Whiteflies, Helleborus, Disease-resistant plants

PAL Question:

I have a white fly infestation on Helleborus. Is there any natural control (Rodale recommends tobacco tea) -- anything less labor intensive?

View Answer:

According to The Organic Gardener's Handbook of Natural Insect and Disease Control, edited by Barbara Ellis (Rodale Press, 1996), whitefly can be controlled in the following ways:
- Catch adults on yellow sticky traps.
- Vacuum adults from leaves.
- Attract parasitic wasps and predatory beetles.
- Spray with insecticidal soap, kinoprene (Enstar) or garlic oil.
- Last resort: spray with pyrethrin.

Season Summer
Date 2006-08-11
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Keywords: Pruning trees, Magnolia

PAL Question:

I have a Magnolia tree that is planted next to our house. This year, there were not very many blooms and the tree is getting rather bushy-looking. When is the best time to prune it and how much can be pruned?

View Answer:

According to the American Horticultural Society's book, Pruning and Training by Christopher Brickell (DK Publishing, 1996), mature Magnolias should not be pruned unless it is essential. Many species will bleed from pruning wounds, and should only be pruned from summer to before midwinter. Summer-blooming Magnolias can be carefully pruned to reduce size by removing selected branches. The book Pruning: A Practical Guide by Peter McHoy (Abbeville Press, 1993) recommends doing this in late fall or early winter.
Below is a link to an interesting discussion on the how's and why's of pruning a Magnolia, from University of British Columbia Botanical Garden's online forum.

Season Summer
Date 2008-01-31
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Keywords: Sawflies, Ribes, Disease-resistant plants, Master gardeners, Fruit--Diseases and pests

PAL Question:

We moved into a new house which has a large currant or gooseberry bush. Now that it has leafed out there are numerous caterpillars eating the leaves. I know they are not tent caterpillars, but I cannot identify them. They are whitish-green with yellow bands across the top and bottom, with many black dots or bumps. The head and first six legs are black. It would be nice to learn more about them.

View Answer:

I cannot make a conclusive pest identification remotely, but there is a possibility these caterpillars are currant sawfly, or imported currantworm. Here is some information about this pest from Colorado State University Extension.

If this pest is the culprit, the book, The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale Press, 1996) recommends using Pyrethrin spray, spraying into the center of the bush.

For a definitive pest identification, you may want to bring a sample of the pest and its damage to a Master Gardener Clinic. Using the following link, you can locate a Master Gardener Clinic in your part of Washington State.

Season Summer
Date 2008-01-31
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Keywords: Picea, Trees in cities, Trees--Care and maintenance

PAL Question:

We just moved into a new house that has a beautiful 20-foot-tall Colorado blue spruce planted too close to the house. Can it be topped and shaped so it could be left in that spot? If we wanted to remove it and plant it somewhere else could we do that? Or will it just die anyway? What to do?

View Answer:

I would not recommend topping the tree. Since this tree can reach mature heights of 30 to 60 feet or more, it may not be the right tree for the site. Here is a page about Colorado blue spruce (Picea pungens) from University of Illinois Extension's Selecting Trees For Your Home.

Here is information from a local organization, Plant Amnesty, on why topping trees is not a good solution to your landscaping problem.

This organization has an "Adopt-a-Plant" service, if you think you would like to give the tree away. There are also referral services available from Plant Amnesty if you need the tree removed or moved to another location. You could also contact a certified arborist through the International Society for Arboriculture.

I would suggest looking at resources like Great Plant Picks, which lists trees and shrubs which will do well in our area, and includes information on their growth habits and ultimate size at maturity.

Season All Season
Date 2008-01-31
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Keywords: Apples--Diseases and pests, Malus domestica

PAL Question:

I have a question regarding apple trees and the caterpillars. We have a great apple tree, that I have just noticed has the early nest of these crazy caterpillars that we get around here. Can you help me with the most effective way to get rid of these things before they hatch and start eating our tree???? Is spraying ok for the fruit??

View Answer:

It is possible that your apple tree has an infestation of tent caterpillars, but without seeing the pests, I could not say definitively. If this is what you have, the information below from Washington State University Extension should be of use.

Also, check out Washington Toxics Coalition's page on managing tent caterpillars. You should be able to prune out the affected part of the tree and dispose of the nest.

Season Summer
Date 2006-12-08
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Keywords: Hardy plants, Alstroemeria

PAL Question:

Is there a list of the more cold hardy Alstroemerias?

View Answer:

Here is some general information on Alstroemeria from North Carolina State University Extension, which indicates they are generally hardy to 23 degrees.

The Royal Horticultural Society's A-Z Encyclopedia of Garden Plants, edited by Christopher Brickell (DK PUblishing, 1996) says Alstroemeria aurea and A. ligtu and their hybrids are able to tolerate brief drops in temperature to 5 degrees Fahrenheit.

Season All Season
Date 2006-12-08
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Keywords: Vegetable gardening, Potatoes

PAL Question:

I would like to know how to grow potatoes; how/where best to plant, type of soil, sun/shade requirements, how to tend them, how much fertilizer, when to harvest. I would really like a step-by-step process.

View Answer:

I recommend the book, Growing Vegetables West of the Cascades by Steve Solomon (Sasquatch Books, 2007, 6th edition).

The author says it is important to maintain loose soil around the forming tubers so they can expand well. He recommends planting when all danger of frost is past. Your main crop should go in between May 15 and June 1. Plant the seeds in rows 4 feet apart, dropping seeds one foot apart in the row. Your soil should be open, fertile, and moist below the growing row, and very loose, airy and dryish above and around the forming tubers. Cover seed just barely with well-tilled fertile soil, and then gradually hill up a mixture of soil, compost, and decaying vegetation over the growing vines. This cover should remain loose until harvest time. The ideal planting spot is where fava beans have overwintered and been tilled in shallowly. At planting time, sprinkle complete organic fertilizer in a foot-wide band down each future row. Broadcast a half-inch layer of compost over the row.

Seed potatoes should be free of viruses, which means you should purchase certified seeds. The best are "single drops," small potatoes of about 2 ounces each.

When vines appear, they begin rapid growth. When they are 4 inches high, hill them up by using a hoe and scraping a little soil up around the vines. Repeat this process weekly for the first 2 months, and by midsummer you will have continuous mounds about one foot high and 18 inches wide. Vines will begin to fall across the mounds. Now just handpull any weeds, and avoid disturbing the soil.

Varieties recommended are Yellow Finns, Nooksack Cascadian, Red Gold, Caribe, and Kennebec.

Here is some additional growing information from University of California at Santa Cruz's Center for Agroecology and Sustainable Food Systems.

Season Spring
Date 2006-08-11
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Keywords: Shrubs--Care and maintenance, Syringa, Transplanting

PAL Question:

I have a dark purple lilac tree growing on the north side of my home. It does not get a lot of sunlight. I am wondering about replanting it somewhere else in the yard. When can I do this?

View Answer:

Lilacs should be able to tolerate moderate shade, according to The Plant Care Manual by Stefan Buczacki (Crown Publishers, 1993). You can move it to a sunnier location to see if it will thrive there.

The best time to transplant a lilac is before it leafs out (late winter, when it is dormant) but apparently they are somewhat tolerant of being moved at less-than-ideal times. The University of British Columbia Botanical Garden discussion forum also recommends transplanting lilacs in dormancy. Blooming should not be affected, unless your bush is already leafed out and in bud.

Season All Season
Date 2006-08-11
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Keywords: Prunus lusitanica, Soil testing, Soil amendments

PAL Question:

Some of my Prunus lusitanica (Portugal laurel) shrubs are changing the color of the foliage and stems. Normally the leaves should be dark green and the stems are a dark cranberry red. The soil here at the coast is very sandy. I have put composted manure (the type from bags), fertilized them, and added a bit of lime to the soil around the trunk and close to the root zone. I have not seen much of a response. Do you know what is the optimal pH for Prunus lusitanica? I am concerned about these shrubs because I just planted them last summer.

View Answer:

Prunus lusitanica tolerates a wide variety of pH and moisture levels in soils. See California Department of Forestry SelecTree webpage about this plant.

According to the webpage of a local Seattle garden writer, the leaves do change color slightly, acquiring a bluish tinge in late fall to winter. She also says that Prunus lusitanica does not like wet feet.

What colors are the leaves turning? You might consider testing the soil, to make sure things are not out of balance. Here is a link to the Miller Library website's links about soil testing.

Is it possible that the bagged manure was still hot, that is, not fully aged? If so, that could cause problems.

You might also bring in photographs or sample leaves to a Master Gardener Clinic for diagnosis. You can locate a Master Gardener Clinic within Washington State at this website.

Season Summer
Date 2006-12-08
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Keywords: Jasminum, House plants

PAL Question:

How can I find out about the best way to care for a jasmine plant indoors. The plant is without a species name and I know there are many types of jasmine. Mine has rather robust leaves, and is an active "entwiner". The flowers are white and about the size of a nickel.

View Answer:

The Houseplant Encyclopedia by Ingrid Jantra (Firefly Books, 1997) says that Jasminum likes a full sun, airy location, and should be taken outdoors in summer. During the winter it prefers temperatures of 46-50 degrees Fahrenheit. In summer, keep the root ball moist, and feed every two weeks. In winter, water just enough to keep the plant from drying out. If it is kept in too warm a spot in winter, it may be susceptible to aphids.

Here is some information from British gardener Alan Titchmarsh:

    Indoor jasmine

  • Flower time up to 6 weeks
  • Which room? east or west window, south in winter
  • Temperature max 15C (60F), min 4C (40F), humid

The house plant jasmine (Jasminum polyanthum) bears loose sprays of delightfully fragrant flowers. It is an ideal plant for a cool conservatory or porch which is kept frost free during the winter months. Otherwise, keep it on a well-lit windowsill. Jasmines like a moist atmosphere so mist the leaves regularly and stand the pot on a tray of moist gravel. They are vigorous climbers, so you will need to prune them to keep them small or provide a larger support in subsequent years.

Here is a link to some general information on caring for jasmine plants, from the Chicago Botanic Garden.

Season All Season
Date 2006-08-24
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Keywords: Control of wildlife pests, Thuja plicata

PAL Question:

I have a medium size cedar in my yard. Squirrels have been stripping the bark off - it is reddish and seems to come off fairly easily in flexible strips a few to several inches long. I wonder if I should be concerned about this affecting the health of the tree and if so what I should do to protect it.

View Answer:

It is possible that the bark-stripping may cause lasting damage to your cedar tree. Here is a document on managing squirrel damage from the British Columbia Ministry of Agriculture and Lands. Here is an excerpt:
"The location of bark damage on a tree varies among tree species and is probably related to the ease of bark removal and bark thickness, and hence to the growth characteristics of different species. Basal damage (within 1 m of the ground)is the most common type of damage in beech (Fagus sylvatica). Crown damage frequently occurs in the main canopy of oaks and many conifers, while stem damage usually occurs between the base and canopy in, for example, sycamore (Acer pseudoplatanus), beech, birch (Betula spp.), larch (Larix spp.), and lodgepole pine (Pinus contorta). [...] Crown damage affects the growth and appearance of the tree; severe crown damage kills it. Damage to the base and stem is cumulative occurring over a number of years. Wounds tend to callous over, hiding the damage until the tree is felled. Trees girdled by excessive stem or basal damage will die."

There are various methods of discouraging squirrels, but nothing is a fail-safe approach. The book, Outwitting Critters, by Bill Adler, Jr. (HarperPerennial, 1992) suggests dried blood fertilizer, ultrasonic devices, or live-trapping with peanut butter and small fruit as bait.

Washington State Department of Fish and Wildlife's website has a page which includes suggestions on how to protect trees from squirrels.

Season All Season
Date 2006-08-24
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Keywords: Iberis sempervirens

PAL Question:

I have noticed Candytuft spreading to different places in my yard. Is it considered an invasive or is it okay?

View Answer:

Candytuft (Iberis sempervirens) is not normally considered invasive. It may be especially happy with the conditions in your garden, and it should be fine to continue growing it, unless you dislike its proliferation.

Here is an information page about this plant from the Missouri Botanical Garden website. Note that it says: "Stems may root where they touch the ground creating new plants which can be left as is or transplanted to other areas."

Season All Season
Date 2006-08-24
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Keywords: Failure to fruit, Vaccinium, Plum, Prunus

PAL Question:

We have three blueberry bushes of different varieties that have been bearing just fine over the last several years. This year one of them bloomed heavily and looks like it's generating a good crop. The other two only had a few flowers. What could account for this? Is there anything we should be doing to encourage blooming and fruiting?

I am also wondering when we will ever see fruit on the Italian Prune tree I planted several years ago. It was already pretty big when we bought it, and now it is about 2 inches caliper near the base and is about 12 feet tall. Is there anything we can do to encourage some fruit on this? I do not even remember seeing it bloom this year. Could it have something to do with the weather patterns?

View Answer:

One problem might be a lack of bees. There could also be other reasons, such as Botrytis blossom blight, and blueberry shock virus.

Here is a page from Oregon State University which has some good general information on growing blueberries .

Is it possible that the blueberries have become dense and twiggy? If they are not pruned, they may become unproductive. The information below is from University of Florida Cooperative Extension:

Pruning mature blueberry plants is largely a matter of cane removal or cane thinning. The objective of pruning mature bushes is to stimulate the proper balance of vegetative and reproductive growth, and limit plant size. Pruning stimulates the development of new canes which are more productive than older canes. A general rule is to remove about 1/4 to 1/5 of the oldest canes each year (usually one to three of the oldest canes). This will result in continuous cane renewal so that no cane is more than three or four years old. Pruning to reduce the number of flower buds may also be required on some southern highbush cultivars which set heavy crops such as 'Misty'. Flowers should always be removed from one and two-year-old plants by pruning or rubbing them off before fruit set occurs. Most pruning is usually done immediately after harvest during the early summer. Removal of some of the flowers buds to adjust the crop load is usually done during the late winter just before growth begins.

As for the Italian prune, a plum tree may not begin to bear until it is 3 to 6 years old.

You may also want to visit a Master Gardener Clinic with your questions. You can locate a Master Gardener Clinic within King County on this website.

Season Spring
Date 2007-04-03
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Keywords: Woody plant cuttings, Propagation, Salix

PAL Question:

I know you can plant willows from cuttings, but what about weeping willow trees? Can they be grown from a cutting (by an amateur)? If so, how?

View Answer:

Following is a suggestion from American Horticultural Society Plant Propagation, ed. by A. Toogood, 1999, p. 89.
"The most reliable method for propagating weeping willow (Salix babylonica) is by cuttings. Hardwood cuttings of vigorous willows may be as long as 6 feet and planted out immediately to mature faster than standard 8 inch cuttings. Take cuttings in late autumn from new, fully hardened wood that does not need to be very woody. Line them out in open ground, pot them, or place them in bundles in a frost-free sandbed to root. Select those in active growth in spring to pot. Cuttings may also be taken of green or semi-ripe wood. "

Here is additional information from a British nursery called JPR Environmental:
"The best way to propagate weeping willows is first to find a mature tree that you like the look of and then go and ask the owner if you could take a small branch from it in the winter (most are happy to oblige and will tell you about their tree in great detail!).
"Once a source has been identified then look to prepare the ground. Make sure that the site is not near the house and not near any old water pipes etc. - it would be a shame to have to cut it down just when it is getting a good size. A site near water is good, willows like moist soil but do not do well in soil that is waterlogged for long periods. Dig a square pit say 18 inches wide and deep. Break up the soil and add some compost if the soil structure needs it.
"Now is the time to take a cutting. The best time of year is whenever the leaves are off the tree with the optimum being February to early March - so long as there is not a hard frost on the ground. The branch should be between 1 and 2 inches at the base and not more than 6 feet tall. Plant it in the hole that you have made, firming up the soil so that you cannot pull the branch out. If you are in a windy site it may be worth staking the tree and a rabbit guard will protect it from grazing in the first year or so."

Season Fall
Date 2008-01-31
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Keywords: Ficus carica, Fruit ripening

PAL Question:

The house that we purchased and moved into last spring came complete with a gorgeous, huge fig tree. It is currently full of gorgeous, huge figs, all rock-hard. It is planted against a south-facing wall, so it gets lots of reflected heat, but of course that is diminishing by the day.

So two questions:
1) Is there anything we can do to encourage at least a few figs to ripen before it is too late and
2) Is there anything worth doing with under-ripe figs?

View Answer:

I found information originally published in the summer 2009 issue of Edible Toronto about ways to increase the chances of figs ripening on the tree in cooler climates. In an article entitled "Fig Fetishists in Ontario," author Steven Biggs says:
"The real secret to coaxing the fruit to ripen in our climate is to gain a few days of ripening time. Ferreira shows me a couple of trees over which he's draped clear plastic bags. This creates a warm microclimate around the tree, helping it to come out of dormancy more quickly. Once the current year's growth is underway and figs are forming, another trick is to break off the tip of the branch, leaving four leaves on the current year's growth.
What's Ferreira's big secret? Extra virgin olive oil. In the first week of September, he looks for figs that don't seem as if they will ripen before winter, and puts a drop of extra virgin olive oil on the eye. After six or seven days, he repeats the step. While this doesn't work on all of the fruit, he says, it helps some to ripen."

Most sources warn against using unripe figs. Not only would they not be tasty, but according to the Purdue University's New Crop Resource, "the latex of the unripe fruits and of any part of the tree may be severely irritating to the skin [...]It is an occupational hazard not only to fig harvesters and packers but also to workers in food industries, and to those who employ the latex to treat skin diseases."

Season All Season
Date 2008-01-31
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Keywords: Prunus mume, Prunus

PAL Question:

I would like to know how well the following trees will do in the Seattle area ?
(1)Prunus mume var. 'Matsubara Red'
(2)Prunus 'Kiku-shidare-zakura'

View Answer:

Both species you mention should do well in the Seattle area. Prunus 'Kiku-shidare-zakura' is described in Arthur Lee Jacobson's Trees of Seattle (2006). Its other common name is 'Cheal's Weeping Cherry.' The Japanese name means "weeping chrysanthemum cherry." Its form is arching and weeping from the point where it has been top-grafted. According to Jacobson, the tree tends to be gawky and a bit sparse, but the flowers are very double. It is common in Seattle.

Prunus mume is also listed in Jacobson's book. This tree and its cultivars (such as 'Matsubara Red') are less common in Seattle. You might be able to see examples in the Seattle Japanese Garden, the Kubota Garden, or Seattle Chinese Garden.

Because the common name of Prunus mume is Japanese apricot, there is sometimes confusion between Japanese flowering cherries and apricots. Prunus mume does produce fruit, but they are small and "bland to somewhat bitter," and in Japanese cuisine they are preserved in salt and used as a condiment (Umeboshi plum). The more familiar fruiting apricot tree is actually Prunus armeniaca (and its cultivars).

Season All Season
Date 2008-01-31
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Keywords: Salad greens, Edible greens

PAL Question:

Is it safe to boil or steam French frisée lettuce (as one would with spinach and chard)? Does cooking the lettuce this way make it poisonous or inedible?

View Answer:

Frisée lettuce (Cichorium endivia) is not actually a lettuce, as this link from Yuma County (Arizona) Cooperative Extension says, but a leafy green related to endive and chicory. It is sometimes called curly endive, French endive, or escarole. There are at least 18 varieties. Leaves are eaten raw in salads, boiled, steamed, sauteed, braised, or cooked in soups and stews.The mature plants are sometimes blanched before harvesting to reduce the bitter flavor. In Java, they are pickled in brine.
Source: Cornucopia II; A Source Book of Edible Plants, by S. Facciola, 1998, p. 190, 362-363.

Frisée (confusingly called French endive by some) is almost a miniature version of curly endive or perhaps is more like the inner portion or heart of that plant. The outer leaves of frisée are light green to yellow, and the yellowing continues inside and becomes white at the center with a lace-like pattern with a milder taste than that of curly endive.
Source:
http://www.tonytantillo.com/vegetables/chicory.html

Frisee: A great little lettuce that is part of the chicory family. It is lacy and pleasantly bitter. As the lettuce grows, each head is tied up so that the sun does not penetrate the center of the lettuce as it finishes growing. This process blanches the frisee since the plant needs the sun to develop its normal green leaves. The delicate white leaves are considered a delicacy and are the least bitter.
Source:
http://www.cheftalk.com/content/display.cfm?articleid=50&type=article

Season All Season
Date 2008-01-31
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Keywords: Crocosmia, Pruning

PAL Question:

Can Crocosmia be pruned or cut way down? When? The tall leaves are looking ungainly.

View Answer:

According to The Plant Care Manual by Stefan Buczacki (Crown, 1993), you should cut back the foliage as it discolors.

According to the Royal Horticultural Society, perennials that produce leaves and flower stems from below the soil level, such as crocosmia and peony, are cut back to soil level.

Season Fall
Date 2008-01-31
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Keywords: Rosa, Pruning

PAL Question:

I would like to know when is the best time of year to prune back (heavily) the roses in my garden. I have read that winter is best, when they are dormant, but I have also read spring is the right time.
Also, with roses that are possibly 20 years old or more, and have very woody stems, is it all right to prune them back to the woody (brown parts)? Or should I not cut back past the green parts?

View Answer:

In the Pacific Northwest, most sources recommend pruning in late fall or early spring. Where to cut depends on the type of roses you have (modern, climbers, shrub, etc.).

The Olympia Rose Society also provides excellent pruning information.

You don't mention what type(s) of roses you are hoping to prune, but the June/July 2011 Organic Gardening article by E.J. Hook, former gardener at the Woodland Park Rose Garden, covers basic pruning techniques for the 5 main types of rose.

Season All Season
Date 2008-01-31
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Keywords: Quirky, Salvia hispanica, Seeds

PAL Question:

Chia seeds: what are they, and what are they good for, besides sprouting on clay animals (Chia Pets!)? Lately, I'm seeing them promoted everywhere for their health benefits. Is there any validity to this?

View Answer:

The common name Chia refers to several species of Salvia, and to Hyptis suaveolens. The species that is imported into the United States is usually Salvia hispanica. Purdue University's New Crops database has information about the uses of chia seeds:
"The seeds of chias have been eaten for centuries by native North Americans, either raw or parched. They are used in sauces and as thickening agents. When soaked in water the seed envelops itself in a copious mucilaginous polysaccharide, excellent for digestion, and together with the grain itself forms a nutritious food. Mixed with orange juice the gel-like seeds make a nutritious breakfast and can help to control excess weight. Users report that a glass full of orange juice with a teaspoon of presoaked seeds leaves one feeling full and without hunger until noon. The plant explorer Edward Palmer wrote (1871): 'In preparing chia for use the seeds are roasted and ground, and the addition of water makes a mucilaginous mass several times the original bulk, sugar to taste is added, and the result is the much prized semi-fluid pinole of Indians and others, and to me one of the best and most nutritive foods while traveling over the deserts.'"

The New York Times published an article (11/24/2012) on the current trend for consuming chia seeds as a nutritional supplement (purportedly high in antioxidants and omega-3 fatty acids). More studies are needed to substantiate the health claims, as this information from Columbia University's "Go Ask Alice" website points out:
"People eat chia seeds for diabetes, high blood pressure, and to reduce the risk of heart disease and stroke. However, there is currently no good evidence to support chia consumption for these uses. People have also tried using chia seeds as a weight loss aid, as the high fiber content is thought to suppress appetite and ultimately help with weight loss. There's not much support for this claim. One study found that eating chia seeds had no effects on body weight, body fat, or changes in appetite over a 12-week period. However, studies have shown that a particular variety of chia seeds, marketed under Salba, can reduce certain risk factors for heart disease such as blood pressure, clotting factors, and inflammation."

Season All Season
Date 2013-03-23
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Keywords: Pruning shrubs, Shrubs--Care and maintenance, Calluna, Erica

PAL Question:

How do I care now, in the fall, for very well established, huge (in some cases) Callunas? Do they get sheared? If so, how many times a year, and how far back? Also, how do I prune my heaths?

View Answer:

The American Horticultural Society Pruning and Training Manual, ed. by C. Brickell, 1996, p. 183, 193 recommends pruning Calluna (heather) in the same way as Erica cinerea. Prune or trim lightly in early spring, cutting stems back where possible to strong shoots below the spent flower cluster.

Local pruning expert Cass Turnbull of Plant Amnesty says the following about heaths and heathers (Erica and Calluna) in her Guide to Pruning (Sasquatch Books, 2006): "Spring bloomers are sheared shortly after blooming (in the spring). Summer/fall bloomers are also sheared in the early spring (just as new growth starts), so that the attractive seed heads are left in view all winter. An annual light shearing is all that is needed. Don't wait. Do it now before the plants get too old and woody. When cut too far into old brown, barren branches, a plant may not break bud and green back up. If you have inherited a mature yard, it may be necessary to severely prune an old neglected heather. It will either regenerate or die. Probably the latter. An exception is the tree heath, Erica arborea, which (...) responds well to radical renovation."

For further information, consult the following websites of nurseries specializing in these plants:
Heaths and Heathers
Dayton Nursery

Season Fall
Date 2008-01-31
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Keywords: Ribes, Planting

PAL Question:

I received a gift today, a shrub/plant named Ribes sanguineum 'Inverness White,' and different neighbors have different ideas of where to plant it.

I only have a little shade in my garden. Will it take full sun, or does it need partial shade? How tall and wide will it get?

View Answer:

In my experience, Ribes sanguineum does best in partly sunny (or partly shady) sites, and does not need much water once established. The plant you have is Ribes sanguineum var. glutinosum 'Inverness White.' This cultivated variety is described by California Flora Nursery as 6 feet tall and wide, but plant size will vary with garden conditions.

University of California Berkeley Botanical Garden's spring 1999 newsletter features flowering currant selections, including the one you have:
"Ribes sanguineum var. glutinosum 'Inverness White' is a proven fast grower with wonderful white flower clusters. As the flowers fade they develop a rosy cast, giving a bicolored effect. The typical form of this variety has pale pink flowers. Roger Raiche found this one on Inverness Ridge in Marin County, and it has since made its way around the state to various gardens, both public and private. This plant was featured, with other new introductions, at a national meeting of the American Association of Botanical Gardens and Arboreta [...]"

Season All Season
Date 2008-02-07
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Keywords: Aquilegia, Edible wild plants, Poisonous plants, Edible landscaping

PAL Question:

I've been reading up on permaculture and exploring the edibility of common ornamental plants. Several books I've looked at suggest that columbine flowers (Aquilegia canadensis and Aquilegia vulgaris, specifically) are edible. I have my doubts, since columbine is in the family Ranunculaceae, which I would generally consider poisonous. What do you think?

View Answer:

I think you are right to question your sources. Although some species of Aquilegia have ethnobotanical uses as food, you should still proceed with caution. I found information about edible and medicinal uses of Aquilegia formosa. Daniel Moerman's Native American Food Plants, Timber Press, 2010, mentions that the Miwok boiled and ate the early spring greens, and that children of the Hanaksiala tribe sucked nectar from the flowers. In her book Ethnobotany of Western Washington (University of Washington, 1979), Erna Gunther mentions medicinal and edible uses of this species of columbine. The Quileute tribe used the sap to aid in healing wounds, and Chehalis children sucked "honey out of the flowers." However, The North American Guide to Common Poisonous Plants and Mushrooms by Nancy Turner and Patrick von Aderkas (Timber Press, 2009) lists Aquilegia species as toxic:
"Most [members of the Ranunculaceae] contain irritant protoanemonins; columbines contain cyanogenic glycosides."

Columbine is included in University of Vermont Extension's list of "Potentially Harmful Perennials." St. Olaf College's page on wild columbine points out a common confusion between the blossoms of honeysuckle and columbine:
"Young children often mistake Columbine for Honeysuckle, pulling off the flowers and biting the spurs in search of nectar. Though no official records of toxicity have been reported for Columbine, it belongs to a family which contains other toxic species. Caution is advised."

The Plants for a Future database of edible and medicinal plants lists a number of species of columbine. Here is their page on Aquilegia canadensis. I don't find myself convinced by the statement that "the flowers are probably perfectly safe to eat." The entry for Aquilegia vulgaris says that the flowers are "rich in nectar, they are sweet and delightful, they make a very attractive addition to mixed salads and can also be used as a thirst-quenching munch in the garden. The flowers are also used as a tea substitute." It is worth looking at the sources cited at the end of this entry, to decide if you feel they are trustworthy. To summarize, when in doubt, don't eat the columbines (or any other plant whose edibility is debatable)!

Season All Season
Date 2011-12-30
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Keywords: Trillium, Transplanting

PAL Question:

My native trilliums (the beautiful white ones that have now faded to purple) are thriving in my woodland garden. I would like to know when the best time is to dig up a clump to share with a friend.

View Answer:

According to Michael Leigh's Grow Your Own Native Landscape (Olympia, WA: Native Plant Salvage Project, 1999), dividing Trillium is difficult because you must "dig deeply to ensure minimal damage to roots and rhizomes, take special care not to break the stems, and transplants may die back before reappearing the following spring." According to April Pettinger's Native Plants in the Coastal Garden (Whitecap, 2002), "Trilliums do not like to be transplanted, so if you decide to move them to another site, be prepared for them to take several years to flower again." My personal experience suggests that taking as much of the soil around those rhizomes as possible will give the plant the best chance of success, and I think early fall is the best time, although I don't find any source that specifies a time of year. Right after bloom may be fine too, as it is the recommended time for division according to the American Horticultural Society's Plant Propagation (DK Publishing, 1999).

Season All Season
Date 2010-04-21
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Keywords: Genista, Spartium junceum, Cytisus, Noxious weeds--Washington, Allergies

PAL Question:

My question is about Cytisus. People with allergies complain about the Scotch broom that grows wild. Are the other tame varieties like C. x praecox going to be a pollen allergy problem also? I want to plant it as an informal hedge and my customers are worried. I want to tell them there is no comparison in the plants. Am I right?

View Answer:

To answer your second question first, Scotch broom (Cytisus scoparius) is an invasive European species that has given all brooms a bad name. Spanish broom (Spartium junceum) is also invasive, and is considered a Class A noxious weed in Washington State. There are garden-worthy brooms such as C. x praecox. A staff member here grew one in her previous garden for many years (and loved it). Some species of Genista, such as Genista stenopetala, are reportedly not invasive.

According to the book Allergy-Free Gardening by Thomas Leo Ogren (Ten Speed Press, 2000), Cytisus ranks 5 on the allergy index scale of 1 to 10, but allergy to this plant is uncommon, except in areas where there is a lot of it growing. Spartium junceum rates a 7, while Genista rates a 4, about the same as a begonia or a primrose.

Season All Season
Date 2006-12-08
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Keywords: Acer palmatum, Control of wildlife pests

PAL Question:

The bark on a Coral Bark Maple is peeling away on one side of the trunk...about 1 1/2 to 2 feet long. The tree looks healthy otherwise. Cause? Anything to do?

View Answer:

Trees (maples and others) are attacked by various diseases and pests, but nothing that removes sections of bark on a trunk. Damage might be from larger pests such as raccoons, deer or squirrels. In the city, squirrels often strip bark from trees for their nests. You might want to:

1. Put chicken wire or other protective barrier around the tree. The tree will heal itself as long as the entire trunk is not girdled (that is when bark is stripped all the way around the trunk so moisture and nutrients can't flow).

2. Have an arborist look at the tree for an accurate diagnosis. To locate an arborist in your area, contact Plant Amnesty's referral service or call their Referral Service Coordinator at 206-783-9813 and leave the following information:

Name
General Location (city or town)
Phone Numbers (work, home, cell)
Email (will get the quickest response!)

Season All Season
Date 2006-10-05
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Keywords: Potted plants, Australian plants, Pruning trees, Eucalyptus

PAL Question:

I recently purchased two Eucalyptus gunnii trees and one E. dalrympleana, which are still in their pots. I have them in full sun, facing south. I have been watering them every day - is this appropriate? I know that the gunnii tolerates waterlogged soil.

View Answer:

All Eucalyptus prefer full sun and well-drained soil. They are very drought tolerant when established.
Source: Manual of Woody Landscape Plants, by M. Dirr, 1998, p. 352.

If your plants are in terracotta containers they will need daily water. If they are in non-porous containers you have a bit more leeway, but do not let them dry out while they are young.

Another consideration is whether you plan to grow these trees in containers permanently, or if you are going to be moving them into the garden. If you plan to keep them in pots, bear in mind that these trees will get quite large (70 feet tall by 20 or more feet wide), so you may end up needing to do a lot of pruning from the top as well as root pruning. Sometimes, even when planted out into the garden, urban gardeners with small lots will coppice a tree like Eucalyptus gunnii or E. dalrympleana annually so that it does not overgrow its site, and so that the rounded, juvenile leaves are maintained. See the Royal Horticultural Society's page on eucalyptus pruning for additional details.

If your plan is to move the trees into the garden, it is best to do it when they are relatively young and small, as Eucalyptus generally dislikes root disturbance.

Season All Season
Date 2006-10-05
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Keywords: Schizachyrium, Plant care, Transplanting, Ornamental grasses

PAL Question:

Schizachyrium scoparium seems to me to be difficult to transplant. They die on me when moved. What could I be doing wrong? The time of year? Adequately watered?

View Answer:

According to the Color Encyclopedia of Ornamental Grasses, Schizachyrium scoparium requires full sun, prefers good drainage or sloping ground. Does not persist on highly fertile soils or in excessively moist conditions, and suffers if the crowns are crowded by mulch.


Propagate by seed or by division in spring.


Grasses are sensitive to soil level, especially when young. Ideally, the crown of the grass should sit just slightly above the soil surface. Planting too low can rot grasses and planting to high can cause them to dry out and die.


Mulch of all sorts can be an efficient method of controlling weeds and conserving soil moisture. Many species, such as Schizachyrium scoparium, cannot tolerate having mulch pushed up around their crowns, a practice that often promotes rot and disease at the base of the plant.

Source: Color Encyclopedia of Ornamental Grasses, by R. Darke, 1999, pp. 121, 276.

Season All Season
Date 2006-10-05
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Keywords: Silene, Plant identification

PAL Question:

I am having trouble growing Silene (do not know the species). It has magenta flowers with notched petals on two foot stems and hairy basal foliage. I have killed four plants that were planted in four different locations. I am able to keep hundreds of other plants alive in my garden, but not this one! It flowers profusely from mid April through July. Then the leaves start wilting, and before long, it is dead. The only thing I can think of is that it needs superior drainage. Could I be overwatering it?

View Answer:

You may have one of the annual types of Silene, which die after setting seed. It is really hard to know for sure since there are over 500 species. You may be able to identify your Silene in the book Lychnis and Silene in the Garden, by J.L. Jones, 1999.

There are some magenta-colored species of Silene with notched petals (Silene dioica and Silene hookeri for example), as you describe. These are alpine or rock garden plants that prefer well-drained conditions and do not like highly acidic soil. It is certainly possible that you have overwatered or that the soil in which they are planted doesn't drain sharply enough or is too acidic.

Season All Season
Date 2006-10-05
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Keywords: Euonymus, Fungal diseases of plants

PAL Question:

I am considering using Euonymus 'Green Spire' for a hedge. My experience with Euonymus japonicus is that every year it seems to get mildew and drop leaves. Is this likely to happen with the 'Green Spire' as well? Do you have any suggestions about how to treat the mildew or avoid it?

View Answer:

'Green Spire' is a variety of Euonymus japonicus. This plant can suffer from a fungus, Oidium euonymus japonici, which occurs only on Euonymus japonicus, and is found wherever the host grows. Clemson University Extension says that fallen leaves and heavily affected branches should be disposed of. Plant in a sunny site which is not overcrowded, and do not water from above.

According to University of California, Davis's Integrated Pest Management site, variegated forms of Euonymus are less susceptible to mildew. Preventive measures are the first step, but if your plants already have mildew, this resource lists less toxic fungicides, such as Neem oil, jojoba oil, baking soda spray, potassium bicarbonate, and biological fungicides: "With the exception of the oils, these materials are primarily preventive, although potassium bicarbonate has some eradicant activity. Oils work best as eradicants but also have some protectant activity."

Season All Season
Date 2006-10-05
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Keywords: Tomatoes--Care and maintenance

PAL Question:

I purchased an heirloom tomato at Home Depot (I know) and planted it deep in a pot in about the middle of June. I put the pot in a very sunny spot, I have fed it twice and watered it daily. It grew like crazy, then slowed when it began to show fruit. Now it is full of fruit but nothing wants to ripen. I removed a tomato today that had split.

Is there anything I can do to help the tomatoes ripen?

View Answer:

A few suggestions:
--Do not fertilize the plants any more, as this mostly stimulates growth rather than fruit ripening.
--You can drape clear plastic over the plant to keep the temperature up, especially at night, just make sure to remove it during the hottest days so you do not cook the plants.
--Stressing the plant by cutting the roots with a spade 8-12 inches from the stem will encourage ripening. Underwatering will also stress the plant.
--Remove any flowers and really small fruit that probably will not ripen anyway to encourage the plant's energy towards the developed fruit.
--If you still end up with green tomatoes, bring them inside before the first frost, they may ripen on the windowsill.

Also available in many bookstores or libraries (including the Miller Library) is Growing Vegetables West of the Cascades, by Steve Solomon

Season Summer
Date 2006-10-05
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Keywords: Stipa, Propagation

PAL Question:

Can 'Giant Feather Grass' (Stipa gigantea) be propagated by division or by seed only? What are the requirements for successful propagation?

View Answer:

You can propagate Stipa either by division or by seed. According to the A-Z Encyclopedia of Plants and the AHS Plant Propagation books, both ways need to be done in the spring. Specifically, seeds should be sown in containers in a cold frame in spring. Divisions should be done from mid-spring to early summer.

Seeds should be sown when you can maintain a temperature of 59 degrees F. Most grass seed germinates in a week. Transplant seedlings one to a pot or cell as soon as they are large enough to handle. Transfer pots of established seedlings to a frost-free place to grow. Plant out in mid-spring.

Divisions - cut back the foliage for easier handling, then lift the clump. Shake loose soil from the roots or wash clean, to make it easier to separate them. Use a sharp knife to divide the clump into good-sized sections. Trim any overlong or damaged roots. The divisions can then be replanted in the garden.

I have also noticed that in my garden, Stipa usually reseeds itself and if you look carefully you may find some small seedlings already started, which you can transplant.

Season Spring
Date 2006-10-05
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Keywords: Seed borne plant diseases, Plant diseases--Diagnosis, Cyclamen

PAL Question:

I am a collector of Cyclamens and grow most of my collection in pots. I believe my C. purpurascens are infected with Botrytis, though I have not had this confirmed by any tests. Last year was particularly bad and I had to remove nearly every leaf from both my plants. This summer, as the new leaves emerged, I sprayed the leaves and surface of the grit with a sulfur solution, which seemed to dramatically reduce the infection rate. Now, the infection seems to be back. Can you suggest some methods of control? Do I have to have it confirmed first? I repotted them early this summer, and sterilized the pots and replaced the grit at that time. What else can I do?

View Answer:

What you have done to control Botrytis is what is recommended by the Pacific Northwest Plant Disease Management Handbook. It does indicate the Botrytis can be seed-borne and grow systemically in the plant. Your real solution may be to obtain plants that are certified disease free.

However in researching Botrytis online, I found an article, "Botrytis Blight of Flowering Potted Plants" in Plant Health Progress, from Plant Management Network International. This article was written by a researcher at Cornell University who suggested that Cyclamen are also susceptible to Fusarium wilt and that the symptoms are quite similar. Therefore, I do think it would be wise to take a sample of your diseased plants to a Master Gardener clinic for confirmation. The Master Gardener clinics in Thurston County can be found at their website.

Season All Season
Date 2006-12-08
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Keywords: Ixia, Plant care

PAL Question:

I am very interested in corn lilies growing in the Seattle area, and I would like to know how to grow them and where to find some.

View Answer:

At this time of the year, corn lilies (Ixia) have already done their flowering, and I do not know of any place to send you to see them.

Regarding how to grow these bulbs, the following is quoted from Sunset Garden Book (2001), pp. 406-407:

African Corn Lily:
Clump of narrow, almost grasslike leaves sends up wiry, 18-20 inch stems topped by short spikes of 2 inch flowers in late spring. Each six-petaled blossom opens out nearly flat in full sun but remains cup-shaped or closed on overcast days. Colors include cream, yellow, red, orange, and pink, typically with dark centers. Most Ixias sold are hybrids of the South African species Ixia maculata.

Grow in well-drained soil. Where winter lows usually stay above 20 degrees F, plant corms in early fall, setting them 2 inches deep and about 3 inches apart. ... Let soil go dry when foliage yellows after bloom. Where corms will not be subject to rainfall or irrigation during dormant period, they can be left undisturbed until the planting becomes crowded or flowering declines. When this occurs, dig corms in summer and store as for gladiolus until recommended planting time in your area (the nursery can tell you this). Where corms will receive summer moisture, dig and store them after foliage dies back; or treat as annuals. Potted corms (planted close together and about 1 inch deep) can be stored in pots of dry soil.

Season All Season
Date 2006-10-10
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Keywords: Fruit trees--Washington state, Heirloom varieties, Fruit trees

PAL Question:

I am interested in planting fruit trees on our treeless property. Can you recommend any sources of bare-root HEIRLOOM fruit varieties grafted onto modern rootstocks? Or do people who grow heirloom fruits usually use the old rootstocks, too?

I am also interested in finding a descriptive list of how different heirlooms taste, how difficult their pests are to control, and how they do in our region (Puget Sound).

View Answer:

Below are some suggestions:

1. WSU's fruit research station in Mt. Vernon is the best place to learn about history, grafting rootstocks, varieties, etc. Here is an article from the spring 2013 issue of WSU's Washington State Magazine on heirloom apples.

2. There is an event in early October at Cloud Mountain Farm in Everson, Washington. They have a fruit festival where you can taste the fruits and talk with experts.

3. An outstanding book you will probably want to buy (or come to the library to review it first) is Fruit, Berry and Nut Inventory, 4th edition, An Inventory of Nursery Catalogs Listing All Fruit, Berry and Nut Varieties Available by Mail Order in the United States. Edited by Ken Whealy, 2009.
We also have many other excellent reference sources about growing tree fruit.

4. You might consider joining the Western Cascade Fruit Society or the Seattle Tree Fruit Society. They offer courses and events, and are very knowledgeable.

5. The staff at Raintree Nursery near Morton, WA offer a wealth of information about what grows well in the Pacific Northwest, best rootstocks, etc.

Season All Season
Date 2006-10-10
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Keywords: Plant diseases--Diagnosis, Master gardeners, Acer

PAL Question:

I have an uncommon maple (Acer ukuruduense) that I planted two years ago, and which one year ago started sending out long stems from the base, so that now it has a vase shape. One month ago the main (original) stem turned black almost to the ground (the bottom two feet or so are still green), and all its leaves turned brown and fell off. Some of the buds still seem viable, but it seems to be dying at the tips. The rest of the plant is so far showing no signs of trouble. I have not been able to figure out what is going on.

Questions:
1. What is causing this?
2. What, if anything, did I do wrong, and what can I do differently?
3. Might this problem spread to other trees: I have several other small maples in the vicinity.

Other information: The tree is so far just surrounded by bare dirt. This year I watered it frequently with a soaker hose throughout the summer, but last year I was not watering it regularly. It is in full sun, which it is supposed to like.

View Answer:

I am sorry to hear about your diseased maple. Your rare species was mentioned in 2 of our 3 books on maples. However, none of the books describe pests or diseases species by species. The books only give information on "general maple problems." The Gardener's Guide to Growing Maples by James Harris states that maples are "generally trouble-free," but the following can cause problems:
Verticillium wilt, which can kill a tree in a few days, or branch by branch over many years; it is a soil borne fungus that is quite common in Seattle (sorry);
Fusarium, which is another soil borne fungus;
Botrytis, which is a fungus, worst on seedlings, but can also cause die-back on established plants; this fungus favors warm humid conditions;
Die-back, which is not a disease; new growth in fall is not hardened off by winter-time and is killed by cold temperatures.

Take a sample branch into a Master Gardener clinic for a diagnosis (insist they submit it to the CUH diagnosticians if they do not know).

If it is Verticillium you can only slow down the disease by reducing all stress on the tree (keep it well watered and mulched). If your other maples are healthy and established they should be okay, but all are vulnerable to this nasty fungus.

Season All Season
Date 2006-10-10
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Keywords: Plant care, Coleus, Medicinal plants

PAL Question:

I want to know about Coleus forskohlii a plant of South Africa. What growing conditions does it need, and what are its medicinal properties?

View Answer:

The plant you ask about is Coleus forskohlii (also known as 'Plectranthus barbatus') in the family of plants called Lamiaceae. If your growing conditions resemble those of its native range (it grows wild in parts of West Bengal), you may be able to grow this plant.

The article referenced below, entitled "Development of Coleus forskohlii as a medicinal crop", from the Food and Agriculture Organization Document Repository, should give you much information of interest. The document may be found in the online FAO Corporate Document Repository.

Here is an excerpt from the above web document:
Coleus forskohlii grows wild on sun-exposed arid and semi-arid hill slopes of the Himalayas from Simla eastward to Sikkim and Bhutan, Deccan Plateau, Eastern Ghats, Eastern Plateau and rainshadow regions of the Western Ghats in India. Latitudinal and altitudinal range for the occurrence of the species is between 8 degrees and 31 degrees N and 600-800 m respectively. The species was studied for its ecological preferences in its native habitats throughout its distribution range excluding Eastern Plateau, Sikkim and Bhutan. Before the botanical studies were undertaken, the species was studied in the regional floras and herbarium specimens were examined in seven zonal herbaria of the botanical survey of India at Dehra Dun (Himalayan flora), Allahabad (Central India flora), Shillong (northeastern India flora), Jodhpur (Rajasthan flora), Pune (western India flora), Coimbatore (southern India flora) and Port Blair (Andaman and Nicobar group of islands flora), as well as at the Forest Research Institute, Dehra Dun and the Blatter Herbarium in Bombay. Eleven representative ecogeographic areas were selected for habitat and population studies; between 1982 and 1985, 27 botanical trips were made for the purpose. Coleus-growing areas in the Himalayas in Uttar Pradesh were visited every month from April to December, and the other areas were visited at least twice during the blooming period. The following is the summary of the observations made on different populations and habitats of C. forskohlii (Shah 1989).
C. forskohlii is a subtropical and warm temperate species naturally growing at 600-1800 m elevation
The species grows on sun-exposed hill slopes and plateaus in arid and semi-arid climatic zones
The species inhabits loamy or sandy-loam soil with 6.4 to 7.9 pH
The species is herbaceous with annual stems and perennial rootstock

The medicinal uses of this plant have not been evaluated fully for safety. Sloan-Kettering Cancer Center also has useful information about Coleus forskohlii. Here is a brief excerpt: "Very limited data are available concerning the efficacy of forskolin. Most studies performed with forskolin have been human trials; those performed on heart failure and glaucoma are inconclusive."

As with any drug or herbal medicine, you should consult a medical professional if you have questions about its use.

Season All Season
Date 2006-10-17
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Keywords: Plant care, Malus, Plant diseases

PAL Question:

I am looking for a Malus (crabapple), not necessarily native, but is decorative in terms of blooms and foliage. I am also interested in plant diseases. I am hoping for a tree that will mature to about 20 feet with a 20 foot spread. Growing conditions are half shade, half sun, behind a semi-dense fence. We live in the San Juan Islands where the soil is not great and the tree will not get much water past establishment.

View Answer:

Here is what I found about the culture of flowering crabapples from the book Flowering Crabapples, the Genus Malus, by Fr. John L. Fiala (1994), p. 45:

"Crabapple trees luxuriate in full sunlight in deep rich soils that are well drained. Soils with a pH range of 5.0 to 7.5 suit crabapples well, but the ideal pH range is from 5.5 to 6.5. Even if gardeners are fortunate to have ideal soil conditions, they may not be able to allocate the best part of the garden to crabapples. Flowering crabapples, however, are not greedy and will accept almost any soil that is not waterlogged or overly dry. As long as the soil has a reasonable amount of nutrients and water, crabapples manage to do very well.

"Like most plants, crabapples prefer rich sandy loams, but even in heavier clay soils they do better than many other trees and shrubs and seem to bloom well once they are established. They will accept slightly wetter soils than lilacs, for example, but in these heavier soils they should have excellent drainage as they will not grow in waterlogged, swampy areas nor in soils inundated for long periods of time."

Regarding particular trees you might like that would be disease-free, I found a couple of crabapples that were listed in The Pacific Northwest Gardener's Book of Lists,by Ray and Jan McNeilan (1997). This is from page 24:

1. Malus 'Prairiefire' has red foliage when young that matures to deep green, has bright pink/red blossoms and deep purple-red fruit. It grows to 20 ft x 20 ft and has excellent resistance to scab and mildew (Pacific NW scourges).

2. From the book Flowering Crabapples, the Genus Malus, by Fr. John L. Fiala (1994), p. 147: Malus sieboldii 'Calocarpa' (trade name, Redbud crabapple) is a dense, upright to spreading tree, 15 ft high and as wide... buds deep red, opening to single, white to pink-white flowers 1.4 in across; fruit 0.4 in diameter, bright red to red-orange... A reliable, abundant, annual bloomer... One of the most beautiful of all the ornamental crabapples both in bloom and in fruit. Birds relish the small fruit which never is messy.
From The Pacific Northwest Gardener's Book of Lists, p. 25, I found that this tree is rated 'excellent' in terms of resistance to both mildew and scab.

3. Malus 'Strawberry Parfait' is a "vase-shaped, spreading tree 18 ft high and 20 ft wide; leaves red-purple, turning green with maturity; buds red, opening to single, pink flowers in clusters; fruit yellow with red blush, 0.4 inch in diameter. Excellent disease rating but not rated for fire blight [bacterial disease]. Not very ornamental."
From The Pacific Northwest Gardener's Book of Lists, p. 25, I found that this tree is rated 'excellent' in terms of resistance to both mildew and scab.

[Note: fire blight appears to be more the issue in the midwest and eastern U.S.]

Season All Season
Date 2006-10-23
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Keywords: Verticillium, Plant diseases--Diagnosis, Acer

PAL Question:

I want to test the roots of our Japanese Maple for Verticillium wilt. Are there places which could test for that?

View Answer:

There is information about Verticillium wilt and how to manage it on the Washington State University Extension's HortSense website.

To have a sample from your Japanese maple diagnosed, you can take samples to a free Master Gardener Clinic, or you can send samples (for a fee) to WSU Puyallup Research and Extension Center:
go to "How to Submit a Sample," scroll down to "Plant Problem Diagnosis," then you can download a form by clicking on "Form C1006."

My personal experience with this disease is that the Japanese maple lived with it for quite a few years before totally succumbing, at which point we had it removed by an arborist.

Season All Season
Date 2006-10-23
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Keywords: Plant care, Vegetables, Herbs

PAL Question:

What herbs and vegetables grow well in very little sun?

View Answer:

The following is a list of vegetables that can tolerate partial shade. While productions may be greater in the sun, these plants will produce an edible crop when grown in a shady location.


From an article on The Old House Web (no longer available online):

VEGETABLES
Arugula
Beans
Beets
Broccoli
Brussels sprouts
Cabbage
Cauliflower
Celery
Cress
Endive
Kale
Kohlrabi
Leeks
Parsnips
Peas
Potatoes
Radish
Rhubarb
Rutabagas
Salad Burnet
Sorrel
Spinach
Summer Squash
Turnips

HERBS
Garlic
Angelica
Borage
Caraway
Chervil
Coriander
Parsley
Lemon Balm
Lovage
Mint
Tarragon
Thyme

This article ("Best Shade-Tolerant Vegetables") in Mother Earth News offers more detail about the amount of sun or shade needed.

Remember that most of these plants do not grow in complete shade. Plants will need some morning, evening or filtered sun; a total of two to six hours of direct sun is the minimum.

Season All Season
Date 2006-10-17
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Keywords: Pruning, Clematis

PAL Question:

We are tearing out an old wood fence and replacing it with a new cedar fence, 6 feet high. We have a mature Clematis montana rubens growing on the old fence, prolific in growth and bloom, that I would very much like to save. Can I save it? We will have to start taking the old fence down right away. The new one is being installed next week, so I cannot wait until fall, which would probably be a better time to cut it back. Where do I begin pruning? Where do I stop? Anything I can do to lessen the shock to the plant?

View Answer:

Clematis montanas are in pruning group 1 (or A) which means they do not take well to hard pruning. However, if it is the only way to save your Clematis, it is worth a try.

This is what the British Clematis Society recommends:
Category 1 (or A): No pruning.
"This category includes: C. montana If you wish to prune these types because they have outgrown their space they should be pruned immediately after flowering. You may or may not lose your plant as a result of the pruning. You might want to reduce the plant size over two or three seasons rather than in one go.
How-to: Start at the bottom of the plant and work your way up the stem to the first pair of plump, healthy buds. Prune the stem above the buds and remove everything above the cut. Treat each stem in a similar way."

Pruning is safer than transplanting:
"If a Clematis is to be replanted from an existing site, the late winter before bud break is the time to do this. However, it is only the large-flowered cultivars that generally can be replanted from an open ground position due to their large fleshy roots. The Clematis species and their cultivated forms have a very fibrous root system that usually breaks up when it is being dug up. The montana types are extremely difficult to replant once they have been established for more than two or three years."
Source: The Gardener's Guide to Growing Clematis, by R. Evison, 1998, p. 39).

Season Winter
Date 2006-10-17
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Keywords: Mutation, Chrysanthemum

PAL Question:

I was puttering around in my flower garden and discovered a chrysanthemum that has apparently sported. The same plant has one substantial stem with distinctly different colored flowers. I have never read of this happening before. It is doubtful it is anything but a different color but hey it happened in my garden.

View Answer:

"In common with many other plants the Chrysanthemum occasionally produces a mutation or change called a "sport." This is a variation from the normal for a particular variety. The cells of the part or parts affected change and cause the difference. While this can occur in any part of the plant or bloom, the most noticeable is a change of flower colour. You may for example find that a white-flowered variety has changed to yellow and this can be of any degree from a stripe in one petal to a whole flower, or even the whole plant being affected. Cuttings taken from a whole plant sport are likely to stay the new colour. Where a whole bloom sport occurs they would probably need to be taken from the stem concerned. If only a petal or two, the chances of fixing it are rather slim."
Source: A Plantsman's Guide to Chrysanthemums, b y J. Woolman, 1989, p. 115).

So it is fairly normal, but interesting anyway!

Season All Season
Date 2006-10-23
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Keywords: Hydrangea, Fertilizers

PAL Question:

I have a few Hydrangeas that have not been doing their best. I think I have the exposure down, and their colors. I need advice on what fertilizer is best for them and when, how much and how often to apply it. I try to stay as organic as possible.

View Answer:

According to Hydrangeas: A Gardeners' Guide by Toni Lawson-Hall and Brian Rothera (Timber Press, 1995), hydrangeas do not generally require special feeding. If you wish, you can apply a general fertilizer twice a year. "As important as feeding, and in fact another method of supplying nutrients, is mulching." The authors suggest using mature compost or leaf-mould. Mulching in the spring to a depth of about 3 inches will help protect the roots of your hydrangeas from drying out (but never put mulch directly up against the base of your shrubs). Mulching also suppresses weeds. Since you garden organically, mulch may be your best bet for supplying a slow and gentle dose of nutrients. If the plants continue to fare poorly, you may want to do a soil test to see if there is some kind of nutrient imbalance that needs correcting.

Season All Season
Date 2006-10-26
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Keywords: Trifolium, Pisum, Vicia, Cover crops, Grain, Garden fertilizers, Legumes, Vegetable gardening, Compost

PAL Question:

We plan to put in a vegetable garden next spring where we now have grass. It is a great sunny spot that we think would work well for this. The question is, after we cut out the sod this fall, someone has suggested we plant rye grass for the winter, is this a good solution? If not, what do we do to the soil this winter? (We plan to bring in some top soil after we take out the sod).

View Answer:

There are several approaches that you can use to get your new garden ready. One is from Growing Vegetables West of the Cascades by Steve Solomon. He recommends removing the grass, covering it with no more than 1/2 inch of completely rotted compost or 1 inch of raw ruminant manure, and spread agricultural lime at 50 pounds per 1,000 square foot. Do this in early October. Then scatter small-seeded fava bean seed at 6 to 8 pounds per 1,000 square feet. Rototill no more than 2 inches deep and relax until May. In late May you rototill deeply and or spade in the overwintered garden area. Then you can plant.

Another information source, Seattle Tilth's Maritime Northwest Garden Guide, recommends using an annual winter cover crop to improve the soil. It suggests using 85% legume and 15% grain for maximum nitrogen fixation. For the legume, you can use Field peas, Crimson clover, Fava beans or vetch. For the grain you can use cereal rye, winter wheat, spelt or barley. Most of these are applied at about 2 pounds per 1,000 square feet. Again you would rototill or turn under the cover crop in late April or May.

Solomon's method will provide a better total approach. You also should consider having your soil tested to find out what is missing and what your pH level is.

Season Spring
Date 2008-03-27
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Keywords: Phormium, Vegetative propagation, New Zealand plants

PAL Question:

Can I divide New Zealand flax without killing it? When should I do it? My adult plant, about three years old, has two very healthy looking youngsters that I would like to move.

View Answer:

The best time to divide Phormium is spring, according to American Horticultural Society's Plant Propagation (DK Publishing, 1999), but what you are describing are new offsets, so you will not be splitting the entire crown of the plant, but instead separating them from the parent plant. Wear gloves when working with Phormium. You may be able to use two garden forks to separate the youngsters from the parent.

Season All Season
Date 2006-10-26
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Keywords: Failure to flower, Hydrangea

PAL Question:

I have two Hydrangeas growing up the side of my house in a northeastern exposure. This will be their 4th year. Leaf growth is robust... flower growth almost non-existent (on one of the shrubs, one bloom last year; one forming this year). What can I do to encourage bloom or should I start over?

View Answer:

According to the Hydrangeas! Hydrangeas! website, there could be several reasons why yours are not blooming well. Check out their page, "Why Won't My Hydrangeas Bloom?"

There is another useful resource that may be of help. Try Why Plants Fail to Bloom, by Leonard P. Perry, a professor at the University of Vermont Extension. Perry suggests there are five possible reasons: Age, Temperature, Alternate Flowering, Light, Nutrition and Pruning.

In addition, I consulted two books on hydrangeas. Both mentioned that Hydrangea anomala subsp. petiolaris can take time to bloom. According to Michael A. Dirr's Hydrangeas for American Gardens, Time is [the climbing hydrangea's] biggest ally. That is, once it gets established, there is no stopping it.
Michael A Dirr. Hydrangeas for American Gardens. Timber Press, 2004. p. 24.

Toni Lawson-Hall's Hydrangeas: A Gardener's Guide also says that Hydrangea anomala subsp. petiolaris "grows well on north-facing walls but takes a while to get established."
Toni Lawson-Hall. Hydrangeas: A Gardener's Guide. 1995. p. 81.

You are probably wondering how long a while is. Alas, I was unable to locate a specific timeframe for when you might expect those gorgeous blooms to start, but from what I can gather, time may help.

Season All Season
Date 2006-10-26
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Keywords: Artichokes (common), Cutworms, Vegetables--Diseases and pests, Slugs

PAL Question:

I have about 20 healthy artichokes. They did not die back in the winter. I think that there is a lot of bug activity going on in them: earwigs, slugs. Should I cut the plants to the ground and dispose of the possible bugs that have wintered over in them? I hate to do it because the foliage is so lovely.

View Answer:

I have grown artichokes for the last 5 years, so I am going to answer from personal experience.
Do not cut the plants back because they will be sending up their flowers in the next few weeks (depending on the weather, it could be as late as June). Cutting it back now will just delay any flowers for at least 6-8 months, if not kill them outright. While I too have had numerous slugs, earwigs and cutworms, I find that their damage is minimal, and does not hurt the flower show. And for eating I just wash them carefully and then turn a blind eye when I find a few earwigs in the pot after cooking!
Sprinkling some Sluggo (or comparable less toxic slug bait) into the leaf joints will help too.

Season Spring
Date 2006-11-02
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Keywords: Berberis, Plant exchanges and donations

PAL Question:

Do you know of a website or referral service for "recycling" plants? I have about 10 feet of barberry (Berberis) bushes that I want to get rid of and thought if they could be dug up with enough of the roots, someone could use them. They are quite ornamental, birds love them, and the thorns are quite lethal (for me, not the birds).

View Answer:

You can contact Plant Amnesty's Adopt-a-Plant program. You can also try GardenWeb's Pacific Northwest Garden Exchange, or freecycle.

Season All Season
Date 2007-10-27
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Keywords: Plant protection--Law and Regulations, House plants

PAL Question:

I live in Seattle, but am going to Canada for an extended stay. Can I bring my houseplants across the border?

View Answer:

Generally, Canada allows houseplants from the mainland United States, but you may be asked to provide proof of origin at the border. The Canadian government page on guidelines for visitors and seasonal residents spells out the details. Here is an excerpt:
"Houseplants are defined as plants commonly known and recognized as such, which are grown or intended to be grown indoors. Bonsai plants are not considered to be houseplants. If you are importing houseplants from the continental United States as part of your baggage or household effects, you do not need phytosanitary certificates or import permits. For all other plants from the United States, you may require a phytosanitary certificate from the U.S. Department of Agriculture and an import permit from the CFIA."

Season All Season
Date 2010-01-13
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Keywords: mosquitoes, Ponds, Frogs

PAL Question:

I've been noticing creatures in my garden pond that I'm hoping are not mosquito larvae. How can I tell the difference between mosquitoes and tadpoles? I wouldn't mind having frogs, but I don't want to breed mosquitoes!

View Answer:

The following may help you tell the difference between mosquito larvae and tadpoles.
Mosquito (note their hairy appearance):
New South Wales Mosquito Monitoring image 1
image 2
Tadpole (note their smooth sides):
University of Richmond biology professor W. John Hayden's photos

If you are concerned about mosquitoes in your pond, there are a number of preventive steps you can take. Mosquitoes are less likely to thrive in moving water, so you may want to install a submersible pump. Washington State University Extension provides information for homeowners on West Nile virus prevention and mosquito control. Here is an excerpt:
"Manage weeds; keep vegetation short around water. Adult mosquitoes are attracted to dense, tall vegetation around water.
Remove unnecessary floating structures or debris from ponds. Mosquitoes are often found around floating debris.
Keep drains, ditches and culverts clean to allow proper drainage.
Consider stocking ornamental or permanent, self-contained ponds with insect-eating fish, such as goldfish.
Shape pond edges to a shelf or steep slope. Mosquitoes prefer shallow pond edges."

Season All Season
Date 2010-04-10
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Keywords: Carex stipata, Ledum glandulosum, Juncus ensifolius, Juncus effusus, Deschampsia cespitosa, Sambucus racemosa, Athyrium filix-femina, Native plants--Washington, Carex, Rubus spectabilis, Allium

PAL Question:

I am an Ecologist with Adopt-A-Stream Foundation, a non-profit stream restoration organization. I am creating a planting plan for a golf course in Snohomish County. My constraints: Low-growing native shrubs with extensive root systems to help filter out the golf course irrigation water before it enters the stream. Willow would be an obvious choice, but it would grow too tall and out of control. I was looking at such species as Snowberry (Symphoricarpos), Nootka Rose (Rosa nutkana), Salmonberry (Rubus spectabilis), etc. It would have to be a FAC+ (streams and wetlands). Any thoughts?

View Answer:

FAC+ is a wetland indicator status term meaning "Facultative," i.e., more likely to occur in wetlands but also found in non-wetlands.

I found a list in Restoring Wetlands in Washington Publ#93-17 and picked out the FAC-identified ones, eliminating all the tall trees and shrubs. Symphoricarpos (Snowberry) would be a good option, but Rosa nutkana (Nootka Rose) and Rubus spectabilis (Salmonberry) get too big for your purposes. A different rose I could recommend is Rosa gymnocarpa (Baldhip Rose). Many of the following recommendations are grasses of one sort or another. (See the USDA Wetland Indicator status definitions.)

Allium geyeri (non-native) FACU
Athyrium filix femina FAC
Carex aperta (non-native) FACW
Carex stipata FACW
Deschampsia caespitosa FACW
Juncus effusus and ensifolius FACW
Ledum glandulosum FACW
Sambucus racemosa var. melanocarpa FACU
Spirea douglasii FACW

You might also try the Snohomish County Conservation District website.

Season All Season
Date 2006-11-14
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Keywords: Arborist, Evergreens, Pruning trees

PAL Question:

An issue has come up within our local homeowners association regarding some of the evergreen trees in our common areas. The issue is that about 20 or so trees have "deformed tops" - the tree has grown straight, but in the course of nature, the top has either broken off in a storm, or the tree has grown irregularly, developing a "hook" or "lever" at the top of the tree. This has lead to considerable discussion and (unfortunately) argument within our association. A tree service was hired by our association and they recommended "topping" the evergreens with the "lever" on the top. They stated these "levers" become "sails" in the wind and weaken the trees. One side believes these trees are hazardous and should be topped for safety, the other side believes they should be left as they are.

Searching through resources on the internet has led me to believe that topping these trees is the worst thing that could be done for the future health of the trees, not to mention the effect on property values due to the unsightliness "topping" causes.

I am interested in obtaining any information on the subject and would be open to discussing this with an arborist if possible, preferably someone who is very familiar with northwest evergreens.

View Answer:

You are right to be concerned about topping. The discussion probably should be whether to remove the trees if they pose a true hazard, or leave the trees if they do not pose a hazard. A damaged leader can be remedied, but do not take my word for it! You need a CERTIFIED arborist. If the arborist is hired as a consultant he will not have any incentive to recommend work that is unnecessary (this is why I am suspicious of the tree-service company).

Here are two organizations to contact for referrals:
Plant Amnesty: Plant Amnesty (See also Plant Amnesty's page about topping trees.)
PNW Chapter of the International Society of Arboriculture (the organization that grants certification) www.pnwisa.org or www.isa-arbor.com

You want someone who has experience with tree hazard evaluation. Another source is Arboriculture by Harris, Clark and Matheny that discusses what to do when a conifer loses its leader.

Season All Season
Date 2006-11-07
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Keywords: Polygonum cuspidatum, Noxious weeds

PAL Question:

I have a non-native bamboo. It's in a marshy area. It is soft light green. It dries to wood every year. And I cut it like firewood and chip it. Then suddenly it grew back and is growing to an acre size. It even flowers: soft light white vanilla flowers for the bees. Can I rototill it under and seed in native Northwest groundcovers?

View Answer:

It is difficult to do plant identification by description alone, but it sounds like you may have Japanese Knotweed (Polygonum cuspidatum) It is extremely (!) hard to control this plant. Rototilling it will make hundreds of new plants because it grows from the tiniest root fragment, so do not do that! There is a lot of good information on it on the Internet, but here are two good links:

King County, which lists it as a Class B noxious weed (control recommended but not required by law)

Season All Season
Date 2006-11-07
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Keywords: Tulipa, Planting, Narcissus, Bulbs

PAL Question:

Bulbs in pots - when to plant?

Daffodils & tulips wilting in pots now, what to do with them? Can you put them in the ground right now, or should you wait till fall? Keep them dry, wet, what?

View Answer:

Yes, you can put them in the ground right now or you can lift them, keep them dry and plant them in the fall. Growing in pots is stressful to bulbs, so you may find fewer flowers next year.

Most tulips do not flower reliably each year, even if they were grown in the ground, so many people treat them as annuals (dig up and toss!) BUT some tulips do re-flower (Darwin Hybrids, Fosterianas and species tulips) so if you are not sure what you have, go ahead and replant. Both tulips and daffodils dislike summer water, so make sure you either plant them in a place where they will stay dry or make sure they are planted in really well-drained soil. Mixing gravel into the soil can help with drainage.

Season Spring
Date 2006-11-07
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Keywords: Acer palmatum, Plant diseases

PAL Question:

I have a lovely, 3-ft. Japanese Maple (Acer palmatum) that has access to full sun. I am guessing it is over 3 years old at least. The tree is leafing beautifully, but last week I noticed there are "pustules" all over the stems and branches. They are yellowish-brown in color and somewhat mottled looking. They form in irregular clusters along the branch. Each pustule is about the size of a ladybug; in fact, at first I thought they were beetles, but they do not move and when I removed one, it was liquid-y inside and left a thin, white streak along the branch. I am a beginner/ homeowner, so I do not know what this is. Do you have any ideas? What can I do to treat this? I would hate to lose my Japanese Maple.

View Answer:

The best way to determine if your tree is diseased is to bring a sample to a Master Gardener Diagnostic Clinic and ask a Master Gardener to diagnose it for you. This service is free to home gardeners.

What you describe sounds like several quite different problems (canker, or scale, for instance), which is why having a hands-on diagnosis is so important. Below is general information about maple diseases which you can compare with your tree. Additionally, I recommend the book Japanese Maples by J.D. Vertrees and Peter Gregory (Timber Press, 2009). It has sections on the most common pests and diseases affecting Japanese maples.

My Garden Guide from Bartlett Tree Experts has a document about Japanese Maples including extensive information about diseases.

Clemson State University has a factsheet on Maple diseases and insect pests (read the entry on scale).

Try searching for "maple" in Pacific Northwest Guide to Plant Disease Control, and compare the descriptions to see if any ring true with what you are seeing. Ultimately, though, the best thing is to get a hands-on diagnosis from the Master Gardeners, as mentioned above.

Season All Season
Date 2007-05-30
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Keywords: Powdery mildew diseases, Plant diseases--Diagnosis, Rhododendrons--Diseases and pests, Master gardeners

PAL Question:

My rhododendrons have a problem. What appears to be a white powder covers the buds and spreads up the leaves. What is it, and what can I do to stop it?

View Answer:

I cannot be absolutely certain without seeing the plants, but it sounds as if your rhododendrons could have powdery mildew.

Here is an article from the Washington State University Cooperative Extension which describes this disease. One preventive measure you should certainly take is to clean up all the fallen leaves and twigs under your rhododendrons, because the fungus which causes powdery mildew can overwinter there.

You could bring in a sample to a Master Gardener Clinic, and ask if they can diagnose the disease as well (they are at the Center for Urban Horticulture and other locations--see their website.

Season All Season
Date 2006-11-07
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Keywords: Arborist, Trees in cities, Roots--Wounds and injuries, Plant diseases, Fungi, Arbutus menziesii

PAL Question:

We recently bought a house on San Juan Island with lots of beautiful madronas (Arbutus menziesii) on the property. Two of them show no signs of life... others have the occasional dead branch here and there. We have been advised that this is likely caused by a fungus and that it can spread rapidly. We have been shown blackened excavated areas on the trunks of the dead trees.. and similar though less extensive areas on some of the others. What can be done to save our beautiful madronas?

View Answer:

It is possible your trees are suffering from canker fungus (Nattrassia mangiferae), or some other type of fungal disease. Here is a link to a file called "The Decline of the Pacific Madrone" edited by A. B. Adams (from a symposium held here at the Center for Urban Horticulture in 1995): http://soilslab.cfr.washington.edu

You may want to call a certified arborist to look at the trees, determine the extent of the disease, and help you decide whether the trees can be salvaged. (Search the Pacific Northwest Chapter of the International Society of Arboriculture for a local arborist.)

Below is a response to a question similar to yours from the University of British Columbia Botanical Garden and Centre for Plant Research:

"What you describe are the classic symptoms of 'Arbutus decline,' which is postulated in the literature as being caused by mostly naturally-occurring, weakly pathogenic fungi, made more virulent by the predisposition of Arbutus to disease, caused by urban stresses, especially root disturbance." (see also: "Arbutus Tree Decline" from Nanaimo. B.C.'s Parks, Recreation and Culture department)

Nevertheless, I am convinced that much of the die-back we are seeing on established Arbutus trees stems not from disease, but primarily from the complications of damage, competition, shading and especially, drought stress (we have had a run of very droughty summers). Typically, the most affected natural stands of Arbutus are very dense, with poor air-circulation, internal shading and intense competition for resources (characteristic of rapid growth after clearing). And because this region is becoming increasingly urbanized, with more vehicular and marine traffic (marine traffic evidently accounts for a huge proportion of the pollution in the Fraser Basin air-shed), I would not discount atmospheric pollution as a contributor to the decline (one more stress).

I think the reason your shaded trees are not as affected is that their roots are probably deeper and less exposed, and there is reduced evaporative demand on the leaves. However, as the shade increases, these plants, or at least their shaded branches, will succumb.

What to do? I do not think there is anything you can do to save the existing trees, except, perhaps, to minimize human influence around them. You should avoid both disrupting roots and damaging above-ground portions of the trees (with pruning, for example), as any wound is an open invitation to disease-causing micro-organisms. Interestingly, a friend of mine who kayaks has seen black bears foraging for fruit in the tops of Arbutus trees on Keats Island (he should have told them they are not helping the situation any).

Irrigation of established plants is nearly always counter-productive because it encourages surface rooting (which is typically short-lived and considerably less resilient than deep rooting), and summer irrigation is worse, as Arbutus are well adapted to our conditions (at least, where we find them growing naturally) and normally somewhat dormant in summer. You can plant more Arbutus, as a previous correspondent in this thread has, to replace what you are losing, but there is no guarantee that these plants will survive the next drought or indeed, your well-intentioned meddling. (I suspect his plant was lost for the same reason most young Arbutus are lost--by root damage from saturated or compacted soil conditions). The natural succession on your island is probably (as elsewhere in similar places along the coast) tending toward open Douglas fir forest with a few scattered Arbutus in the more inhospitable places. In other words, you can plant what you will, but the larger the Douglas firs, the fewer Arbutus will be able to survive around them. Neither species is particularly shade tolerant and resources are pretty limited on rocky ground, where both prefer to grow locally. Expect change.

Season All Season
Date 2008-03-19
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Keywords: Sambucus, Pruning

PAL Question:

I have two different elderberries that I would like to prune.
1. The first is a 'Sutherland Gold' (a cultivar of Sambucus racemosa) that is 5 years old, and I have never pruned it.
2. The second is a 'Black Beauty' (a cultivar of Sambucus nigra) that I just bought last year.
When should I prune? At what point on the stems? How far from the ground?

View Answer:

I consulted Peter McHoy's Practical Guide to Pruning, (Abbeville Press, 1993), and he recommends cutting one stem in three in mid-spring on plants that have been established for three or more years. You would cut to just above the ground level, choosing to prune out the oldest and weakest shoots first. Continue with cutting out shoots that will open up the center of the plant or improve its shape. It may look sparse afterwards, but new shoots will grow and fill in the space.

If you are growing the plants mainly for their foliage, he suggests cutting all the shoots back to 1-2 inches from the framework of the old wood in mid-spring.

Below is some more detailed information from the website of the Ontario Ministry for Agriculture, Food and Rural Affairs, which assumes you are growing the plants for their fruit production.
Pruning:
"During the first two seasons plants should be encouraged to grow vigorously with little to no pruning required. After the second year, pruning should be done annually in early spring. All dead, broken and weak canes should be removed. Three-year-old canes should be removed as they produce less fruit and appear to be more prone to winter injury. Removal of older canes will encourage the growth of new, more fruitful canes.
"Mowing of all the canes in a mature planting may be a method of reducing labour costs while encouraging growth of new canes. The disadvantage of this system is that there is a loss of production in the season following mowing as there is limited production on the one-year-old canes."

Season All Season
Date 2006-11-14
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Keywords: Vinca, Lamium, Lavandula, Ground cover plants, Ceanothus

PAL Question:

Our house is on a corner lot. The side yard has a very small slope with big rocks along the edge. Presently it has a variety of flowers such as lavender that bloomed last summer. However, my question is what kind of ground cover can I put there, other than grass, that would look good and be evergreen.

Secondly, there are two big pine trees at the corner. What are my options for plantings beneath these trees that would give it a pulled-together look?

View Answer:

I am guessing that the spot receives a good amount of sun, since you have lavender Lavandula that flowered there in the summer. Were you looking for a groundcover that will tolerate people walking on it, or did you want somewhat taller plants that will blend well with the lavender?

If you plan to walk on the area, you might want to consider chamomile (Chamaemelum nobile) or creeping thyme (Thymus serpyllum).

There are many great choices for plants not intended to be walked on, and I recommend that you take a look at some of the resources we have in the Miller Library so you can find the plants that most appeal to you. I recommend the books Gardening with Groundcovers and Vines by Allen Lacy (HarperCollins, 1993), and Perennial Groundcovers by David MacKenzie (Timber Press, 1997) as starting points.

Plants that are evergreen (or 'ever-grey') and might go well with lavender are Santolina, Helianthemum (sun rose), Teucrium chamaedrys (germander), and Ceanothus thyrsiflorus (creeping blue blossom ceanothus).

For the spot under your pine trees, you will need plants that tolerate shade and do not have large root systems. I would try Lamium (dead nettle), which comes in several foliage and flower colors, and I would avoid Lamium galeobdolon, a species which is considered a noxious weed in King County. Vinca (periwinkle) might also work. The Lady Bird Johnson Wildflower Center has information on planting beneath pine trees.

Season All Season
Date 2006-11-14
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Keywords: Grafting, Woody plant propagation, Juglans

PAL Question:

Is it possible to graft a walnut scion onto a maple tree?

View Answer:

The book, Plant Propagation edited by Alan Toogood (American Horticultural Society/DK Publishing 1999) says that Juglans regia and Juglans nigra, grown for their edible nuts, are usually whip-and-tongue grafted. You would "use a slightly narrower scion than the stock so the thinner scion bark will align with the stock's cambium more easily."

I was not able to find any information on grafting a walnut scion onto a maple, but here is an article (pdf) on propagating Eastern black walnut trees by William Reid, which has detailed information.

This publication from the University of Georgia College of Agricultural & Environmental Sciences, entitled "Propagating deciduous fruit plants common to Georgia" (1999) indicates that whip grafting or ring budding will work best for walnuts.

Season All Season
Date 2007-04-03
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Keywords: Kochia scoparia, Spartium junceum, Cytisus, Flower arrangement, Noxious weeds--Washington, Corylus

PAL Question:

While living in Japan and practicing flower arrangement, I often used a branch known as ossified broom. It was always available at flower stores there. The color is gray-green, has the typical multiple straight stems as Scotch Broom but also had some thick and twisted branches that are very attractive in arrangements. I would like to plant it so that I would have a ready supply. Can you help me find the correct name?

View Answer:

I consulted a number of books on Japanese flower arrangement, including The Art of Arranging Flowers: A Complete Guide to Japanese Ikebana, by Shozo Sato (Harry N. Abrams, 1965). 'Broom' may be the common name of a number of different plants, such as Spanish broom (Spartium junceum), Scotch broom (Cytisus scoparius), and broom cypress (Kochia scoparia). Unfortunately, these plants are considered noxious weeds in the State of Washington.

You may want to consider a type of broom (Genista or Cytisus) that is not considered invasive.

From your description of the branches, I wonder if the appearance would be similar to Corylus avellana 'Contorta' (Henry Lauder's walking stick).

Season All Season
Date 2006-11-14
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Keywords: Arborist, Hillside planting, Slopes (Soil mechanics), Conifers

PAL Question:

I live in a condo. The conifers on the site are beginning to obstruct the view of the neighbors. Our covenant with these neighbors says trees must not exceed a height of 25 feet. Last year several of the conifers were topped and others removed. Our concern now is that we may have to either top or remove more trees. We don't want to block the neighbors' view but we also don't want to destabilize the ground - we all live on a hillside. What can we do over the next 5, 10, 15, 20 years to decrease the number of conifers and replace them with other trees that will be neighbor-friendly and keep our hill stable?

View Answer:

The short answer is to plant shrubs and groundcovers.

The long answer is that slope stabilization is a serious concern and deserves expert advice. Get started in your research by reading the articles on the WA Dept. of Ecology site:
Controlling Erosion Using Vegetation.

Your condo association may want to hire a consulting arborist and/or a civil engineer ("To locate technical experts such as experienced registered engineers specializing in geotechnical and/or drainage projects, use local telephone directories or call the Seattle or Kitsap branch of the American Society of Civil Engineers (ASCE) for membership references." from DOE site)

For an arborist referral try:
Plant Amnesty

The Pacific Northwest chapter of the International Society of Arboriculture has information about hiring an arborist.

The International Society of Arboriculture can also help to narrow the search to your area.

Season All Season
Date 2006-11-14
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Keywords: Dracaena, Plant cuttings, Pruning

PAL Question:

My indoor Dracaena is getting too tall. I'd like to prune it, and maybe use the cuttings to start new plants. How do I do this?

View Answer:

You should be able to do both tasks. The Complete Houseplant Survival Manual by Barbara Pleasant (Storey, 2005) says "when plants become too tall, cut off the cane at any height. New leaf clusters will grow from just below where the cane was cut. You can cut sections into 6-inch pieces and root them like stem cuttings."

You might also find this discussion from University of British Columbia Botanical Garden's online forum useful.

Here is more information, from University of Florida, which describes how pruning will result in two or more branches forming where the pruning cut was made: "Cut one or two of the stems to a point where new foliage is needed."

You might find more ideas about growing houseplants from cuttings in this University of Illinois Extension page.

Season All Season
Date 2010-04-10
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Keywords: x Citrofortunella floridana, Indoor gardening, Citrus

PAL Question:

I have a Eustis limequat, and it's producing flowers. Should I be taking a brush and dusting pollen from one bloom to the other? Also, I'm growing it inside. Do I need any additional lighting? I have fluorescent lights as well as full-spectrum UVA/UVB lights that I can use. Someone told me I'd need to get really pricy calcium lights, or something similar.

View Answer:

All the resources I've found suggest that citrus flowers are self-pollinating with a very few exceptions. However, your limequat (x Citrofortunella floridana) is growing indoors, so pollination assistance from you will help. Alabama Cooperative Extension describes citrus as generally self-fruitful.
Excerpt:
"With the exception of Clementine tangerine and certain tangerine hybrids such as Orlando tangelo, citrus trees are self-fruitful and do not require cross-pollination. Thus, self-fruitful types of citrus can be grown as single trees. Cross-pollination requires that two or more varieties bloom at the same time. Some varieties will not cross-pollinate each other. Satsuma and navel do not produce viable pollen and thus cannot be used for that purpose."

I looked at several of our books on growing citrus to see if they mentioned any special lighting needs, and Success with Citrus Fruit by Sigrid Hansen-Catania (Merehurst, 1998) simply says that your artificial light source needs to provide 12 hours of light a day, if you do not have a position for the plant near a sunny window. She mentions "specially adapted fluorescent tubes which you can fix to the ceiling about 8-16 inches above the plants," though she mentions it in the context of providing adequate light during winter months.

University of Missouri Extension has a general article on indoor lighting for plants.

This article from Purdue University Horticulture is specific to citrus.
Excerpts:
"Citrus foliage can adapt to the relatively low light levels typical of our homes. However, if flowers and fruit are what you're after, you'll need to give the plants as much light as possible. If natural light is inadequate, you can supplement with artificial lights. A combination of cool white and warm white florescent lights placed close to the plants will help, as will the special 'grow lights' that emit the wavelengths of light most important for plant growth. (...)
If citrus is kept indoors year-round, the plants will likely need a bit of pollination assistance when they do flower. Use an artist's paintbrush or cotton swab to transfer pollen from one flower to another."

The good news is that I don't think you need to invest in any additional expensive lighting systems!

Season All Season
Date 2010-04-10
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Keywords: Myrtus, Rhus, Osmanthus, Screens, Arbutus, Ceanothus

PAL Question:

We are looking for a good screening tree/shrub that is evergreen and interesting. The plant cannot grow over 6 feet high. We have very sandy soil, western exposure, and live in the Magnolia neighborhood. We would like it to be drought tolerant as well. I found Myrtus communis (Myrtle) and Rhus (Sumac)--I am not sure which variety of sumac would be best. I found the information on these plants in the Sunset Pacific Northwest Garden Book. I would love to get your advice on these, and if you have any other ideas as well.

View Answer:

Because of the height limitation of your site, I suggest primarily shrubs (rather than trees) that are evergreen and drought-tolerant.

Most of the Rhus I have seen growing in Seattle is of the deciduous type, but there are several evergreen varieties, such as Rhus virens and Rhus lancea. They are natives of Texas and Baja California. They will not be as hardy as the deciduous varieties.

Myrtus communis does well in seaside gardens although it can exceed your 6 foot height limit, reaching 10 feet or more (according to W. J. Bean, Trees and Shrubs Hardy in the British Isles, 8th ed., John Murray, 1973 and Top-Rated Evergreen Shrubs, Golden Press, 1983). The dwarf variety Myrtus communis 'Compacta,' would be too low-growing to act as a screen.

I would suggest Osmanthus delavayi, which has small, glossy dark green leaves, and very fragrant white flowers in March. It can eventually grow to 8 feet, but is easily maintained as a hedge or screen (see the website Great Plant Picks for pictures and information).
Other ideas would be Arbutus unedo 'Compacta' (Strawberry Tree). Or you could try Ceanothus concha, which has small dark green leaves and blue flowers. The California nursery Las Pilitas has information about this and other varieties of Ceanothus.

You may also wish to come to the Miller Library and browse the many illustrated books on shrubs and trees.

Season All Season
Date 2006-11-28
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Keywords: Lardizabalaceae, Germination, Akebia

PAL Question:

I am looking for information about seed germination of Lardizabala biternata. I am wondering what temperature is best for its germination, if it requires light or darkness to germinate, if it needs to be stratified before germination, and the number of days it takes to germinate. I have the seeds started in my greenhouse at 70 degrees under lights and nothing seems to be happening! I have searched the web and looked at all of my reference books, but do not seem to be able to find this information. The seeds came from Sheffield's Seed Co., Inc. (www.sheffields.com). They do not have any information on their website, although on the seed packet it states that more research is needed!

View Answer:

Below is information on propagating Lardizabala ternata from Plants for a Future.

Propagation
Seed - sow spring in a greenhouse. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in the greenhouse for at least their first winter. Plant out in early summer and, if possible, give the plants some protection for their first winter outdoors. Cuttings of half-ripe wood, 5-10cm long with a heel, June/July in a frame. The cuttings should be put in individual pots. A good percentage. Stem cuttings in spring and autumn.

After locating an article by Dan Hinkley (Washington Park Arboretum Bulletin, Winter 2004), I decided to widen the search to include information on germinating Akebia as well, since they are related.

The California Rare Fruit Growers site has Akebia germination information that might be useful.

The Royal Horticultural Society A-Z Encyclopedia of Garden Plants only says that Lardizabala seed should be sown in containers in a cold frame in spring.

Season All Season
Date 2006-11-28
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Keywords: Woody plant propagation, Salix

PAL Question:

Why do willow trees propagate so easily?

View Answer:

The technical explanation is that willows (Salix) have preformed or latent root initials that will elongate into an established root system when a part of the parent plant is removed.

If you were to take cut willow branches and make a kind of tea by soaking them in water, that water could be used as a sort of natural rooting hormone to help root other types of plants. This indicates that willows naturally contain a high level of the hormone that contributes to root formation.

Season All Season
Date 2006-11-28
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Keywords: Rooting, Fungicides, Plant cuttings, Propagation

PAL Question:

What is the purpose of the chemical in store-brand rooting hormone? I'd rather not use anything with chemicals when I'm propagating plants. Are there alternatives?

View Answer:

The chemical in rooting hormone (usually Indole-3-Butyric acid) acts as a growth stimulator. In commercial rooting hormone formulations, it may be combined with fungicide to prevent the development of fungus/fungal diseases during the rooting process, as is the case with a common brand, Rootone, which contains Thiram (a fungicide). The Environmental Protection Agency has more information about Indole-3-Butyric acid.

If you would rather not use synthetic rooting hormone, you can skip this stage altogether, or you can try making willow water to encourage rooting instead. Oregon State University explains how to make a rooting tonic using willow (page 2).

Season All Season
Date 2006-11-28
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Keywords: Hydrangeaceae (Hydrangea family), Native plants--Washington, Philadelphus lewisii

PAL Question:

What is the specific habitat of the Philadelphus lewisii (wild mock orange)?
What does this plant need from the habitat in order to survive?
What range does the Philadelphus lewisii grow in?
What family is it in?
What other plants does it often grow around?
What specific habitat does it need?
Where does it grow?
Is it an annual or a perennial plant?

View Answer:

Philadelphus lewisii is a Northwest native, a common shrub east and west of the Cascades. According to Trees and Shrubs for Pacific Northwest Gardens, 2nd edition by John A. Grant and Carol L. Grant, it will "thrive in almost any garden soil in either full sun or partial shade, and are of the easiest possible culture. The hybrids respond noticeably to generous cultivation , fertilizer, and water. (It belongs to) the group of summer-flowering shrubs that are best pruned immediately after flowering."

Philadelphus lewisii is a deciduous shrub (in other words, it is not an annual and, although it has a long life span, it is not like an herbaceous perennial that completes its life cycle and starts over the next spring--it is a woody deciduous plant which loses its leaves in winter). (Source: The Royal Horticultural Society A-Z Encyclopedia of Garden Plants, edited by Christopher Brickell; Dorling Kindersley, 1996).

Here is a link to a page from the Washington Native Plant Society about Philadelphus lewisii and its habitat.

It is a Northwest native (state flower of Idaho), and grows throughout Western North America (from British Columbia south to Oregon), southern Europe, and eastern Asia.

The genus Philadelphus grows in rocky woods, semi-desert, and open areas in wet forest. In gardens, it prefers loamy soil and moderate sun.

The genus Philadelphus belongs to the Hydrangeaceae family.

Season All Season
Date 2006-12-19
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Keywords: Pruning shrubs, Buxus

PAL Question:

To renovate old Buxus hedge, when is the best time to cut back to 15-30 cm shoots? It appears that new shoots are pushing through now. My American Horticulture Society Pruning and Training book suggests late spring, but that may not apply to Seattle.

View Answer:

I consulted a local organization, Plant Amnesty, and their information sheet on Buxus says that April is the best time to prune. It is important not to prune when it is either too cold (leaves will turn grey) or too hot (same result).

Peter McHoy's book, A Practical Guide to Pruning, also says to do your renovation pruning in mid- to late spring, and further suggests that drastically reducing the height of the hedge should be done in stages, over two to three years.

Season Spring
Date 2006-11-28
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Keywords: Pruning trees, Malus domestica

PAL Question:

We have an apple tree in our back yard. Last year it produced more apples then we knew what to do with. We pruned it after last season and then this year was an off year and we only had a few apples. My question is do we need to prune it every year or only after a very productive year? We are very new at this so any pruning tips you have would be great as well!!

View Answer:

Many factors may have affected the fruit production on your apple tree, but the general rules on pruning are to prune young trees very lightly, and old trees more heavily, particularly if they have shown little growth.

Pruning is usually done when the tree is dormant (i.e., winter), but sometimes apples are pruned during the summer growing season (the main reasons to do this would be to improve fruit quality and quantity, to regulate growth and control vigor, and to reduce pest and disease problems. (An excellent resource we have here is Training and Pruning Apple and Pear Trees by C.G. Forshey, American Society for Horticultural Science, c1992.) Another thing to consider is whether your tree is a dwarf, semi-dwarf, or standard apple tree. Pruning differs for each of these.

The following factsheet gives basic guidelines for pruning fruit-bearing trees:

Pruning Apple and Pear Trees from Clemson University Extension

Below are useful webpages about pruning fruit trees, and apples in particular:

Pruning Tree Fruit from WSU Extension

Spring and summer pruning for apples from Oregon State University

We have many great books on this subject in the library if you need additional guidance.

Season All Season
Date 2006-12-07
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Keywords: Passiflora, Plant diseases--Diagnosis, Plant diseases, Master gardeners

PAL Question:

I have a passion flower that I brought in for the winter. It has lost all leaves and has sticky little brown spots on it . How do I get rid of the brown sticky things? And how do I get the leaves to grow back. Would putting under a grow light for the winter help.

View Answer:

I read up on Passionflower cultivation and pests in the book Passiflora: Passionflowers of the World by Torsten Ulmer & John M. MacDougal, Timber Press (2004).

Under the section, Overwintering, it says that in winter, passionflowers suffer from lower temperatures, shorter days, and low light, and therefore this season is the most critical period for these plants. Before night temperatures drop below 10 degrees C, the more sensitive container plants, such as Passiflora quadrangularis and P. vitifolia, should be taken indoors. Depending on their resistance to cold, other species will need to be taken to their winter quarters later on; for now, though, these plants should just be cut back and thoroughly scrutinized for pests. Unlike many other decorative plants, passionflowers keep their foliage in winter, with the exception of certain herbaceous species such as P. incarnata, P. lutea, and P. bryonioides. Do you know if your plant is any of those three (so we will know if its loss of leaves is normal and not a sign for alarm)? [This is from p. 49.]

About the brown sticky spots, it is extremely difficult to make a diagnosis or suggest a treatment, sight unseen. If your plant was not supposed to lose its leaves, and the leaf drop is a sign of severe stress, then those spots could be the result of the plant's health being poor (as in low resistance to disease). The spots could be bacteria, viral, fungal or even from some insect (although I read through the list of these and could not tell what it might be).

Your plant would be a great candidate for the Master Gardeners to whom the public can take their plants for advice and diagnosis of problems. I found a Master Gardeners of Ontario, which you can search for your particular region.

Season Winter
Date 2008-02-07
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Keywords: Biennials, Verbascum

PAL Question:

I would like to know a little more about Verbascums. Are they a biennial? Will they reseed themselves? How long a period will they bloom. How tall can they become? Are they invasive? Thank you for you help! I have had very little experience with annuals and biennials.

View Answer:

Verbascum includes 360 species, most of which are biennials, with a few annuals, perennials, and small shrubs, some of which are evergreen or semi-evergreen. The flowers grow on tall upright stems, and while individual flowers are shortlived, there are many of them and they bloom over a long period of time (summer into early fall, in most Seattle gardens).

In my own experience, they can reseed themselves, so if you would prefer not to have your plants do this, just cut off the tall stalk after the flowers have bloomed, and before they set seed. I checked the list of Washington State Noxious Weeds, and did not find Verbascum there, though it can be invasive in other parts of the country (Hawaii, for example).

If you would like information about specific varieties of Verbascum, the Royal Horticultural Society A-Z Encyclopedia of Garden Plants has photographs and descriptions of many of them.

Season All Season
Date 2006-12-07
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Keywords: Hormones, Propagation

PAL Question:

1. Which plants can be rooted only with hormone?

2. Which plants cannot be rooted, even with hormone?

View Answer:

There is excellent general information on plant propagation in The Brooklyn Botanic Garden Gardener's Desk Reference (Janet Marinelli, editor; Henry Holt, 1998), which explains which plants are most successfully propagated by seed, by division, by layering, by leaf or hardwood or softwood or stem cuttings, and by root cuttings.

There really is no resource that will provide a comprehensive list of plants that can or cannot successfully be propagated from root cuttings, but a member of the faculty here who specializes in propagation says that the key element that determines whether a plant can be propagated in that way is age. Each plant has different abilities, and some are easily rooted, such as Salix (willow), while others, like Quercus (oak), or Arbutus (madrona), are very hard to root, especially as they mature. As far as use of rooting hormone, it can help the process, and it will prevent rotting, but if you are a strictly organic gardener, you should be aware that it is a chemical substance.

Season All Season
Date 2006-12-07
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Keywords: Quirky, Catha, Medicinal plants

PAL Question:

Recently I found an Ethiopian man and his wife in my front yard. They were picking the reddened leaves on an otherwise green bush/tree. The man explained this was a "cat" or "Chat" tree, the leaves produce a drugged like state when ingested. He asked me if he could harvest the tree,and not to tell any Somalians, Ethiopians, or Eritrean folk about my tree. He also told me that if I lived in Mogadishu I would be a wealthy man with this tree. He ate some leaves in front of me, and I tried a couple, but they were bitter and unpalatable to a westerner like me. I experienced a feeling of empowerment, strength, and mental alertness. Obviously the "Chat Tree" has some relationship to the "Bongo" young Somalians chew on like a cud.

During the worst of the Anarchy in the late 1990s in Mogadishu there was a lot of news footage of the street gangs, high on the plant they were chewing, and armed with machine guns and machetes, creating havoc.

Do you know the history of this tree?
What are the properties that cause the poisoning?
What is the tree`s botanical name?
Should I report the tree`s existence to the authorities?
Can you tell me what I have here?

P.S.-These trees are common front garden bushes that were widely planted in Perth, Western Australia. Next time I see an African hanging out under one of them, I think I will know why!

View Answer:

The chat, or khat tree, is Catha edulis (Celastrus edulis), and the leaves and branchlets have properties that stimulate the central nervous system. In addition to the euphoric or inebriating properties, chewing the leaves can cause irritability, decreased appetite, gastric upset, constipation, and inflammation of the mouth. Habitual use can lead to periodontal disease, and increased risk of esophageal cancer. The active compounds are Alkaloid D-norpseudoephedrine, as well as other alkaloids, and tannins. (Source: Medical Botany: Plants Affecting Human Health by Walter H. Lewis; John Wiley & Sons, 2003, 2nd ed.)

The Handbook of Medicinal Herbs by James A. Duke (CRC Press, 2002, 2nd ed.) indicates that Catha edulis has been used medicinally to treat a great number of ailments, including asthma, depression, diarrhea, glaucoma, and low blood pressure. Use of khat is an ancient, socially acceptable tradition in the Afro-Arabian culture (and became known as a recreational drug in the USA after American soldiers were exposed to its use in Somalia. Khat is subject to legal restrictions in many countries. (Medicinal Plants of the World by Ben-Erik van Wyk; Timber Press, 2004).

As for whether to report the harvesting of leaves from your tree, that would depend on whether khat use is specifically prohibited by law in Australia.

Season All Season
Date 2006-12-07
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Keywords: Rosa gymnocarpa, Rosa nutkana, Pruning shrubs, Native plants--Washington

PAL Question:

What do the experts recommend regarding time(s) to prune the native roses, Rosa nutkana and Rosa gymnocarpa? I am interested in controlling their growth without losing bloom and/or rose hips. Do either or both of them bloom on second year wood?

View Answer:

Peter McHoy's A Practical Guide to Pruning says that the pruning method would follow that of vigorous species roses, which produce flowers on old wood. He says to remove any dead wood in early spring (similar to 'late winter').

The Royal Horticultural Society A to Z Encyclopedia of Garden Plants (edited by Christopher Brickell, Dorling Kindersley, 1996) says to prune species roses as needed only, cutting out one fifth to one fourth of the oldest stems. A Pacific Northwest native wildlife gardening source on the web recommends only pruning out dead wood, and otherwise leaving it be.

Since Rosa gymnocarpa is also once-flowering, it should be pruned--if you need to prune it at all--just after flowering. The following is a general guide on rose pruning in the Northwest, from the Olympia Rose Society.

Season All Season
Date 2006-12-08
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Keywords: Vegetable gardening, Corn

PAL Question:

Can you tell me some varieties of corn that do well here? I would like to do an early and a midseason variety. Which ones do you like the best?

View Answer:

I consulted Growing Vegetables West of the Cascades by Steve Solomon's, and he says the thing to look for is the number of heat units (HU) required for the corn to reach maturity. Early corn needs about 1,300 HU, later types need over 2,200. We need to choose varieties on the lower end of the HU scale. (Seed catalogs for commercial growers typically have this information, while retail catalogs may not. If you look at a Northwest catalog, such as Territorial Seeds in Oregon, the maturity dates will be closer to our own.)

Solomon lists 'Earlivee' as an early sweet corn variety. In general, he seems to prefer hybrid varieties to open-pollinated, because they may have low yields and less than optimum eating quality, although 'Hooker's Sweet Indian' is one that Territorial carries and which he thinks is worthwhile. He recommends 'Jubilee' as a main season hybrid choice, but says, "It will just barely mature in warmer microclimates around Puget Sound." He recommends choosing small-eared and richly flavored varieties like 'Seneca,' and his final word is that he would grow early corn as the main crop in our area.

The New Twelve Month Gardener: A West Coast Guide has a longer list of recommended varieties, but less detail about their particular requirements and merits: 'Golden Jubilee,' 'Seneca Horizon,' 'Sugar Dots,' 'Bodacious,' 'Chief Ouray,' 'Miracle,' 'Sugar Buns,' 'Jubilee Super Sweet,' 'Seneca Appaloosa,' and 'Golden Bantam.'

Season All Season
Date 2006-12-12
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Keywords: Container plants, Potting soils, Container gardening

PAL Question:

I am doing container gardening -- rather large plantings that will incorporate small trees and shrubs -- and therefore want a potting mix that will last longer than the usual for smaller containers, and will provide some nutrients. I just read about soil-based potting mix, but there is no further info in my text. Can you describe this, and tell me if it commercially available, or do gardeners mix up their own recipe?

View Answer:

There are a variety of opinions about soil-based potting mix. Taylor's Guide to Container Gardening (edited by Roger Holmes, Houghton Mifflin, 1995) provides a recipe for a "real soil" mix combining equal parts garden loam, compost or peat moss, and coarse sand. The sand should be as coarse as possible, and should not be able to pass through a window screen. According to the guide, "the success of any mix using soil depends on the soil's quality." For large pots and planters, the mix should be equal parts coarse, medium, and fine materials (from Landscaping with Container Plants, by Jim Wilson, Houghton Mifflin, 1990), for example:
Coarse material: small nuggets of pine or fir bark
Medium material: pulverized pine or fir bark
Fine material: moistened sphagnum peat moss

The National Sustainable Agriculture Information Service has extensive information on organic potting mixes.

Mother Earth News published an article by Barbara Pleasant in the December 2008/January 2009 issue entitled Make Your Own Potting Soil which should be helpful. The recipe includes pasteurized compost or soil.

Season All Season
Date 2006-12-12
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Keywords: Rosa, Plant exchanges and donations

PAL Question:

I have several immature rose bushes, including some native Washington roses, that must be removed from my property. Are there any organizations, or individuals, who would be interested in transplanting them to another site?

View Answer:

You might want to check out the Seattle Rose Society website, which has lots of good information about roses.

You could also post your information about the roses, or reply to those seeking rose bushes, on the Pacific Northwest Garden Exchange.

Another place that might have an interest in helping to find a new home for your roses is Plant Amnesty.

Season All Season
Date 2006-12-12
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Keywords: Earthworms

PAL Question:

So, here is a weird one for you. I was out in my garden this weekend and I noticed that the dirt paths that I had raked of leaves (but still had a few leaves around) all had small piles of decaying leaves. There were lots of these piles, measuring about 3-5 inches in diameter. When I pushed the leaves aside, I found a small half-inch hole under every single pile. When I dug into the hole, the only thing I found was an earthworm, which occurred in every one. I did not see this on the paths that I had not raked that still had lots of leaves, nor in the garden beds, most of which are heavily mulched with cedar chips.

I know earthworms are major decomposers of decaying leaves and that they mix the organic matter down into the soil. But do they gather the leaves into little bunches? How the heck do they do that?

View Answer:

I know earthworms go out onto the surface at night, grab a leaf or two and bring them back to their hole. I have witnessed this personally in my own garden (usually pathways or nearby).
But why and how?!

The book you need to read is The Earth Moved: On the Remarkable Achievements of Earthworms by Amy Stewart (Algonquin Books, 2004). It is one of those nonfiction books that is written with attention to prose, so I could not find a quick answer, but I am sure it is in there.

Other staff have also observed this, so it is not rare. It seems to be the nightcrawlers that do it. Go out at night with a flashlight to see for yourself.

Season All Season
Date 2007-05-30
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Keywords: Pyracantha, Screens, Thuja, Hedges

PAL Question:

What shrubs or trees will grow quickly to provide a privacy screen above the 6 foot fence between me and my neighbor? My back yard is only about 20 feet from house to fence, and the first 10 feet is a concrete patio.

View Answer:

The classic fast-growing evergreens for hedges are Thuja 'Green Giant' or Leyland cypress (x Cupressocyparis leylandii), but they are a bit boring and because they grow so fast (1-3 ft/yr) it can be a big chore to keep them at a reasonable height. These trees do not stop at 8 feet, but could get to 30-50 feet.

Another fast evergreen is Pyracantha (Pyracantha crenatoserrata to ~8 feet). It is a shrub, but is easily trained/pruned to grow flat. In the past Forestfarm nursery in Oregon has sold both of these, as do most large nurseries. Be aware, however, that this shrub has fierce thorns!

Various types of bamboo could be an option for a fast screen, but plants may be expensive and running bamboo species MUST have a root barrier installed.

Season All Season
Date 2006-12-12
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Keywords: Pruning, Fuchsia

PAL Question:

I have several hardy Fuchsias that are quite large, about 4 - 5 feet tall, that bloomed profusely this year. The leaves are gone now, but when should I prune them? How far back should I prune? Is there anything special I need to know about pruning Fuchsias?

View Answer:

Fuchsias are pretty tough shrubs, especially once established. You can prune just to tidy them up, but it is best to wait until the leaves begin to grow (between March and June).

Here are two links to more detailed information:

From Rainy Side Gardeners, "Some years when we have an exceptionally cold winter, Fuchsias will die down to the ground. Before pruning in spring, wait until leaf buds swell, then prune out dead twigs, or prune down to the ground if winter knocked it completely back."

Another site is the Hardy Fuchsia List from the Northwest Fuchsia Society.

Season Spring
Date 2006-12-14
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Keywords: Lilium (Lily family)

PAL Question:

I am trying to discover the common and scientific name for the orange spotted wild lily that looks like an orange tiger lily. It blooms in the forests of the Pacific Northwest in June and early July.

View Answer:

You must be thinking of Tiger Lily, Lilium columbianum (also known as Columbian lily and Oregon lily). Source: Plants of the Pacific Northwest Coast by Pojar and Mackinnon (Lone Pine, 1994).

Click here to see images of Lilium columbianum.

Season All Season
Date 2006-12-14
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Keywords: Trees, Transplanting

PAL Question:

Can you direct me to information available on the transplant tolerances of different tree species?

View Answer:

There is general information on transplanting trees and shrubs from Morton Arboretum.

There is a table on "Ease of Transplanting" from Principles and Practice of Planting Trees and Shrubs by Watson and Himelick (Int'l Society of Arboriculture, 1997). It is the longest list of any I have found that covers this topic.

Season All Season
Date 2006-12-14
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Keywords: Integrated pest management, Acer

PAL Question:

I have a wood boring beetle in a maple tree and I am wondering if there is a treatment for the tree or do I need to take the tree down?

View Answer:

Here is a link to University of Kentucky's entomology department website that describes insect borers of trees and shrubs.

I also consulted Pests of Landscape Trees and Shrubs: an Integrated Pest Management Guide, second edition, which suggests that prevention is best. If you can make sure the tree is protected from damage, and prune any damaged limbs and branches (should be done when adult borers are not present, Fall through February), this should help, since the borers are attracted to stressed, damaged, or diseased trees. Do not store cut wood near the tree. Insecticide is not considered effective against borers under the bark. If the tunnels are visible and there are not too many of them, you can try using a sharp wire to probe and kill the larvae, but it may be difficult to tell how far to insert the wire.

If the infestation is not severe, you may be able to save the tree by improving its care and its growing environment.

Season All Season
Date 2007-04-03
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Keywords: Throughfall, Thuja plicata

PAL Question:

I am looking for some hard data on the ability of Western red cedar to intercept rain water and the timing of release. Got numbers?

View Answer:

If I am understanding your question correctly, you are asking about the extent to which Thuja plicata (Western red cedar) allows rainwater throughfall. I discovered that there was some research of possible relevance to your topic being done at Evergreen State University as well as at University of Waterloo.

The Miller Library has a book entitled Water in Environmental Planning by Luna Bergere Leopold (1978), which might also be relevant to your search.

Season All Season
Date 2006-12-19
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Keywords: Perennials--Care and maintenance, Narcissus

PAL Question:

I bought a nice kit of paperwhites this year. Now, they are done blooming. The only directions about aftercare are: "After flowering, remove the dead flowers and stems, the leaves should continue to grow." Is this plant ever able to flower again? Can they be planted in the garden, and if so, when? Should I not cut the yellow leaves off, like tulips, until they are all yellow, to promote bulb growth next year? Or should I simply throw them out, as they are not capable of re-blooming?

View Answer:

Most sources I consulted say it probably is not worthwhile trying to get your paperwhites (Narcissus) to rebloom. It can take several years for the bulbs to build up enough energy to rebloom. (If you still want to try this, do not cut off the wilted foliage, store the bulbs in a cool but not cold place, and try planting them out in the garden in spring. Paperwhites will naturalize outdoors in warmer climates--zone 9 or 10.)

Season All Season
Date 2006-12-19
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Keywords: Vaccinium, Planting

PAL Question:

I planted some two- to three-year-old blueberry bushes about a year ago. I may not have transplanted them correctly. I did not loosen up the root system of each bush, did not shake out the soil mixture into which they were potted, and did not spread out the roots laterally within a two- to four-inch depth from the surface. Will my improper planting technique prevent these bushes from producing the gallons of berries that are in my dreams?

On the assumption that I need to pull them up and give them a better start, I have these questions:
Is this a good time of the year to pull them up?

Am I correct in loosening the root ball, shaking out the original potting mixture from the roots, and then spreading out the roots to a shallow depth?

Do you have any other tips for transplanting blueberries?

View Answer:

I wonder if the bushes have been healthy despite your not planting them exactly according to directions. You could wait and see how they perform this year, and then decide if you need to replant them. If you want to replant them in any case, the best time is in the early spring, after the soil has thawed but before bud break (in our climate, you may want to do this in very late winter).

According to The Berry Grower's Companion by Barbara Bowling (Timber Press, 2000), you should remove half of the canes of a mature blueberry bush at the base of the plant. Prune any remaining canes back to 3-4 feet high. Dig around the root ball, taking as big a root ball as possible. (If they look rootbound, then do gently loosen the dirt around the roots). Be sure to have your new planting hole prepared beforehand [...] the width of the hole should be sufficient to spread out the roots, and it should be deep enough to plant them at the same level they grew in originally. Make a bit of a mound in the middle of the hole and array the plant's roots over it, and fill in the hole. Tamp down the dirt gently, and water well. Once replanted, you can mulch around the plants with organic matter, such as grass clippings or straw.

Here is an article from Oregon State University entitled Growing Blueberries in the Home Garden which may be helpful.

Season All Season
Date 2006-12-21
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Keywords: Citrus limon, Insect pests--Control

PAL Question:

I have a lemon tree that is actually not dead yet, but it's not looking good. I had to bring it in late last year as Florence [Italy] was due to have frost for a few days. Then we had horrendous winds and heavy rains. After a few weeks inside, (on a nice sunny indirect-light window sill) it started to drop everything: leaves, blossoms, tiny lemons, and now it is utterly bare. Maybe this is why? On clearing the leaves off the dirt I noticed little blister-like spots on some of the branches. I scraped them with my fingernail and they peeled off, but left sticky stuff behind. Is this a disease? Can I wash the stems? With what? I trimmed the tips of the tiny branches; they are green inside so not dead. I did fertilize with a high-nitrogen liquid, over the leaves and in the pot, a couple of times a month. I have a feeling that spider mites are doing the mischief. Is there hope?

View Answer:

Sorry to hear of your bare lemon tree! The loss of leaves could have been a reaction to the wind, and once the leaves are gone, the tree can become susceptible to waterlogging, pests, and diseases. It is good that you moved it inside, and that it has good light. The blister-like spots on the branches sound like a kind of scale insect, to which Meyer lemons can be prone: California red scale (Aonidiella aurantii). I do not think it would be spider mites, because they would cause stippled, yellowed leaves, and might leave telltale webs. Scale can defoliate and kill a tree. There are beneficial Aphytus wasps that can be used to control scale, but they have to released regularly to be effective and, of course, you would not do this while your tree is indoors. A good reference about scale insects and how to manage them is Pests of the Garden and Small Farm by Mary Louise Flint (University of California Division of Agriculture, 1990)

Here are two recommended books on growing citrus:
Citrus: Complete Guide to Selecting & Growing More than 100 Varieties by Lance Walheim (Ironwood Press, 1996)
Success with Citrus Fruit by Sigrid Hansen-Catania (Merehurst Ltd., London: 1998)

Season All Season
Date 2007-03-20
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Keywords: Christmas trees, Organic farming

PAL Question:

Is there such a thing as a certified organic Christmas tree? If so, where might I find one?

View Answer:

The Washington Department of Agriculture has a list of certified organic producers (current as of 4/17/2014) and on this list I found farms which have carried organic Christmas trees in the past if not currently:
Blue Heron Farm in Rockport, WA
Riversong Farm in Mt. Vernon, WA

Fall City Farms states on their website that, while not certified, they grow their trees using organic practices.
Washington State University's Farm Finder describes this farm as follows:
"They practice ecologically-sound farming and sustainable agriculture and serve as an agricultural education and culinary resource."

The Farm Finder lists a number of other farms which carry "claimed ecologically sound" Christmas trees. The only other farm in King County is Carpinito Brothers in Kent. (There are other farms in other counties.)

In Oregon, there are two types of organic certification, described in this Oregon Public Broadcasting feature:
SERF (Socially and Environmentally Responsible Farm) and Coalition of Environmentally Conscious Growers certification.

This New York Times article, "How Green Can a Christmas Tree Be," by Annie Raver (12/3/2008) mentions there is a certification called "Certified Naturally Grown" for Christmas trees in 47 states.

Another option, if you have the space in your garden, is to buy a living tree from an organic nursery and then plant it.

Season Winter
Date 2012-12-06
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Keywords: Festuca rubra, Poa macrantha, Lathyrus littoralis, Glehnia leiocarpa, Carex macrocephala, Convolvulus soldanella, Abronia latifolia, Elymus mollis, Native plants--Washington, Grasses

PAL Question:

I live in a community on Camano Island. We have some communal beach front property and would like to plant some native beach grasses that are about one foot high. What species do we have to choose from and where can we purchase them?

View Answer:

I found a list of native Northwest beach grasses in an online symposium moderated by Alfred Wiedemann of Evergreen State College in Olympia. (The symposium was about an invasive species, Ammophila arenaria, or European beach grass, which has been crowding out native species.) Here are some of the plants he mentioned:
Elymus (Leymus) mollis (Dunegrass)
Abronia latifolia
Convolvulus (Calystegia) soldanella
Carex macrocephala
Glehnia leiocarpa
Lathyrus littoralis
Poa macrantha

Here is a Seattle Times article from May 1, 2005 about beach plants by Valerie Easton that may be of interest to you. The Miller Library has the book that is mentioned in the article, Native Plants in the Coastal Garden by April Pettinger (Timber Press, rev. and updated, 2002), and it includes a list of native grasses. These two grasses were specifically recommended for beachside gardens:
Elymus or Leymus mollis (also listed above)
Festuca rubra (Red fescue)

Washington Native Plant Society might also be a good resource for you. They provide a list of nurseries in our area which specialize in native plants. King County's Native Plant Guide also has a list of sources.

Season All Season
Date 2007-01-09
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Keywords: Echeveria, Plant care

PAL Question:

I have a start from a large hen & chicks (Echeveria). I have seen these plants grow up to 6 feet tall like a shrub. My start is over two years old. It takes off and seems to thrive, but never gets tall or hardy. It seems to go a year and then the outer leaves wilt. Once it got big enough to tip over, so I am wondering how to give it the right pot and correct soil to allow it to grow. It is located in our west sun room here in the great northwest. Is it alright outdoors in the summer?

View Answer:

I wonder if you have information about the particular species of Echeveria you are growing. Usually, 'hens and chicks' is the common name for Echeveria glauca. The larger growing Echeveria are the ones with "loose, cabbage-like rosettes which reach a foot or more in diameter on heavy stems" (from The Book of Cacti and Other Succulents by Claude Chidamian, Timber Press, 1984).

I consulted Victor Graham's book, Growing Succulent Plants (Timber Press, 1987) for some general guidelines on the best growing practices for Echeveria. He says that the soil you provide should be gritty and on the poor side (for good drainage), and they should not be overfed. In The Succulent Garden: A Practical Gardening Guide by Yvonne Cave (Timber Press, 1997), the recommendation for areas with wet winters such as ours is to grow them in containers on a covered porch or in any sunny spot with overhead cover. In the warmer, drier months they can be placed or planted in the garden without cover. Your sun room sounds like a fine place to grow them during the winter here, although they may prefer morning sunlight and afternoon shade to bring out the best color in their leaves.

The Brooklyn Botanic Garden has a page on growing succulents that may be useful.

Season All Season
Date 2007-01-11
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Keywords: Water-absorbing polymers, Potted plants, Container gardening

PAL Question:

I am doing container plantings for clients (some of them big -- the containers, not the clients), and have water concerns. Have you received any feedback on use of those "soil moist" granules that are supposed to cut down on waterings? My fear is that over time, especially with shrubs in a container, there may be some root rot.

View Answer:

Although there is not any conclusive information on whether use of water-absorbing polymers will contribute to root rot in planters, there are quite a few other causes for concern. Local gardener and writer Jessica Salmonson discusses the matter on her web site, Paghat's Garden.
Here is a brief excerpt:

Many of the 'superabsorbent' properties claimed by polymer manufacturers are exaggerated, and during biodegradation these polymers even reverse their effect, depriving plants of moisture. Woodchips, quality compost, or peat do the same job adequately, plus the woodchips or compost provide safe plant nutrients and a medium for beneficial microorganisms such as polymers retard.

And, inevitably, it turns out that some polymers do in fact reach the foodchain, especially the allegedly safer-to-the-environment biodegradable synthetic polymers. These are fed directly to livestock as feed supplements, are dispersed over crops in herbicides & pesticides, & are mixed into garden soils because of preposterous claims of doing away with a need ever again to water the garden.

Extension horticulturist and Washington State University Professor Linda Chalker-Scott has also written on this issue, and states that even beyond the health and environmental concerns, hydrogels do not work well in clay soils, and can decrease a plant's ability to absorb essential nutrients.

Local garden writer Ann Lovejoy writes about a non-polymer alternative in this article in the Seattle Post Intelligencer: "The newest such water holder I've tried is called Quench. This is a granular, sand-colored material that turns cloudy-translucent in water. Unlike polymers, Quench is based on a natural material (cornstarch) in a form that can absorb up to 400 times its weight in water, right up there with good compost or forest duff. Unlike the usual polymers, this stuff lets go with grace. About 95 percent of the stored water is released to plant roots in midsummer, making plants a lot less dependent on people in hot weather."

Season All Season
Date 2007-01-11
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Keywords: Prunus armeniaca, Fruit trees--Washington state

PAL Question:

I would like to grow some fruit trees on my property; we have room for maybe 2-3 small trees. Do you have any recommendations for the Seattle area? I'm partial to stone fruits -- although I had heard that apricots (Prunus armeniaca) don't do well in Seattle.

View Answer:

I don't think you need to give up on the idea of apricots, as there are a few varieties that will do well here, such as 'Puget Gold' and 'Harglow.' The book, Fruits & Berries of the Pacific Northwest, by David Flaherty and Sue Elen Harvey, also mentions 'Jannes' and 'Tilton' for Western Washington. The book, Pacific Northwest Guide to Home Gardening, by Ray McNeilan and Micheline Ronningen, lists 'Jannes' and 'Tilton,' as well as 'Moorpack,' 'Perfection,' 'Riland,' and 'Royal.' I would also recommend that you look at the catalogs of several Washington State nurseries that specialize in fruit: Raintree Nursery, Cloud Mountain Farm, and Burnt Ridge Nursery. Since you mentioned small trees, you would probably be looking for dwarf forms, depending on the space you have available. These should also be available from the nurseries listed above.

Season All Season
Date 2008-02-07
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Keywords: Gaultheria, Woody plant propagation, Germination

PAL Question:

What specific requirements are needed to germinate Gaultheria procumbens in soilless media?
Any tips on seed stratification, cultural advice, etc., etc.?

View Answer:

The information below comes from the website of Plants for a Future:

"The seed requires a period of cold stratification. Pre-chill for 4-10 weeks and then surface sow in a lime-free compost in a shady part of the greenhouse and keep the compost moist. The seed usually germinates well, usually within 1- 2 months at 20 c, but the seedlings are liable to damp off. It is important to water them with care and to ensure that they get plenty of ventilation. Watering them with a garlic infusion can also help to prevent damping off. Prick out the seedlings into individual pots when they are about 25mm tall, and grow them in light shade in the greenhouse for at least their first winter. Plant them out in late spring or early summer. The seedlings are susceptible to spring frosts so might need some protection for their first few years outdoors. The leaves remain very small for the first few years. If you want to grow from cuttings, use half-ripe wood 3-6cm long, and in July/August place in a frame in a shady position. They form roots in late summer or spring. A good percentage usually take. Division can be carried out at almost any time of the year, but works best in the spring just before new growth begins. Very easy, larger clumps can be replanted directly into their permanent positions, though it is best to pot up smaller clumps and grow them in a cold frame until they are rooting well. Plant them out in the spring."

Another source says to propagate by seed starting in July in a mix of acid peat and sand in a cold frame.

I consulted the book, Seeds of Woody Plants in North America by James A. Young (Dioscorides Press, 1992, rev.ed.), and the general information on Gaultheria states that cold dry storage will help maintain seed viability. G. procumbens has 6800 seeds per gram. Seeds are initially dormant and prechilling is needed for germination (from 30-120 days with a variety of substrata). Salal (G. shallon) seeds appear to require light for germination. This resource says that G. procumbens seeds should be sown in the fall.

Season All Season
Date 2007-01-11
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Keywords: Burl, Abies, Sequoia

PAL Question:

I would like to remove a burl from one of my fir trees. Can I do this without causing harm to the tree?

View Answer:

I was unable to find any information on the incidence of burls (lignotubers) on fir trees (Abies), but I did locate information about redwood (Sequoia sempervirens) burls from a version of The Sempervirens Fund website which is no longer available:

About Redwood Burl
by Chris Brinegar, PhD

"The swollen tissue at the base of some redwood trees is commonly known as a "burl" although scientifically it is referred to as a lignotuber (from the Latin for "woody swelling"). All redwoods have lignotuber tissue but not all have large visible burls. Lignotuber tissue is derived from cells that exist in the tree's seedling stage and then proliferate near the base of the tree as it ages. Buds form within the woody burl and remain dormant until stimulated to grow by damage to the main trunk (usually by fire or logging). The resulting shoots grow rapidly using carbohydrates stored in the surrounding cells and minerals transported through the parent tree's root system. Lignotubers can also form their own roots.

Lignotubers are responsible for vegetative (clonal) reproduction common in redwoods. Without this mode of propagation, the redwood forest would appear far different than it does currently. The second and third-growth redwoods in our coastal forests were generated vegetatively after 19th and 20th century logging of the original forests. If redwoods were solely dependent on reproduction from seed, their numbers would only be a small fraction of what we see today.

Most people think of burl as the "sliced redwood" sold in gift shops and roadside stands, but they do not realize that many of these burls were obtained illegally. There is a growing black market for burl with much of it coming from unscrupulous dealers who harvest it from healthy redwoods on protected forestland. In some cases, removing burl can kill a tree or, at the very least, deface it and reduce its reproductive potential.

Burls can be planted under the appropriate conditions to allow the shoots to form roots and then grow into trees, but the typical buyer of a redwood burl places it in water, watches the shoots grow, then disposes of it after the shoots die from lack of nutrients. If you are determined to grow a redwood tree we suggest that you purchase a small seed-derived tree from a reputable nursery rather than trying to grow one from a burl that may have been acquired through questionable methods."

According to the information here, it seems that by removing a burl, you may risk harming or killing the tree. You might want to contact a certified arborist in your area, and ask them what they recommend. Here is a link to the website of the Pacific Northwest chapter of the International Society of Arboriculture, where you can find lists of certified arborists.

Season All Season
Date 2008-02-07
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Keywords: Poa, Weed control, Herbicides

PAL Question:

Is there a preemergent to use on Poa annua grass in the lawn and if so what is the name and when should it be applied?

View Answer:

According to The Lawn Bible by David R. Mellor (Hyperion, 2003), your best defense against Poa annua (annual bluegrass) is to mow high (2 inches, usually) to shade out weed seedlings; aerate the soil to improve drainage, because weeds thrive in waterlogged soil; and let the surface of the soil dry out between waterings. If one were to apply preemergent herbicide, this would be done in late summer to early fall, but we strongly recommend that you avoid use of herbicides and pesticides in lawn care due to environmental and health concerns. There are effective non-toxic approaches to weed management. Northwest Center for Alternatives to Pesticides has useful information on maintaining a lawn without chemicals.

For another good discussion of this issue, you might want to refer to the book, What the Experts May Not Tell You about Growing the Perfect Lawn by Tom Ogren (Warner Books, 2004).

The University of California, Davis Extension has a document about the management of Poa annua, including specific information on the various herbicides that have been used to treat it but, as mentioned before, it is best to avoid the use of toxic chemicals in the garden.

Season All Season
Date 2007-04-20
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Keywords: Cold protection of plants, Frost, Bulbs

PAL Question:

Do the many bulbs that are rising up to 8" out of the ground need to be covered since the forecast has temperatures down to 17 degrees F these next few mornings?

View Answer:

The bulb foliage should be fine as it is. Any flowers, on the other hand will probably turn to mush. If you're feeling protective or nervous you may want to cover up the foliage with burlap, cloth rags, sheets, etc. Once the clouds come back you can remove the protection.

Here is an article on predicting frost from Organic Gardening magazine.

Season Winter
Date 2007-01-11
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Keywords: Cold protection of plants, Frost, Paeonia

PAL Question:

I have two three-year old Tree Peonies - each in a 30-inch pot. Both have buds - what can I do to protect them from the coming freeze - or will they be ok? The pots are way too heavy for me to move. They are sitting on a blacktop driveway margin. I have no dirt to bury the pots into. Do I wrap them? Would bubble wrap work?

The new one I planted Sunday is covered with an inverted pot - will that be enough?

View Answer:

Your peony (Paeonia) buds will probably be fine, but don't take any chances! Protect the pots with bubble wrap and cover the tops with bed sheets or some other cloth. I think the inverted pot over your new plant should be sufficient. Tree Peonies are quite hardy. The frost would be much more damaging if it came in March or April when plants have leafed out.

Here is an article on predicting frost from Organic Gardening magazine.

University of California's Marin Master Gardeners also has useful tips on how to protect plants from damage by low temperatures. Tree peonies are not among the plants most liable to be harmed by the cold.

Season Winter
Date 2007-01-16
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Keywords: Fargesia, Propagation, Bamboo

PAL Question:

I have a bamboo, Fargesia nitida, 'Blue Fountain Bamboo,' that seems to be blooming this year. Are other specimens of this species blooming in Seattle this year? (I heard a rumor that blooming is synchronized among bamboo plants.) Will it die? Will it produce seeds without a "partner"? I am curious since blooming bamboo isn't something you see every year in Seattle.

View Answer:

My best suggestion is to look at specialist nurseries in your area, or contact your local Parks Department to see if there are any public gardens where you can view other specimens of Fargesia.

As far as the question of whether your plant will die after flowering, here is an article abstract about this subject (which does suggest that the plant will die, but also indicates that this is a time of opportunity to propagate the bamboo).

I also found some general information about propagating bamboo from the American Bamboo Society:

Q. How do I propagate bamboo?

Bamboo is usually propagated by digging up part of a clump of existing bamboo and moving it elsewhere. The vast majority of propagating is done that way and it results in most plants of most varieties in the U.S. being clones. If you divide a bamboo plant and put it in a new location, it usually doesn't do much for the first few growing seasons. The first two years it puts out roots in its new location and usually by the third year it starts putting out larger culms. By the fourth or fifth years it's putting out culms as large as that plant ever will in that location, with that much sun and that much water in that kind of soil.

Bamboo flowers only rarely, (sometimes there's more than a person's lifetime between flowerings) and when it does, it takes so much energy from the plant it often dies. People try various things to save them, like cutting back the culms and fertilizing generously, and sometimes that works.

It can also be propagated via germ plasm. A small number of cells are taken from some part of the plant and grown in glass dishes. Ordinary people don't do this, of course. Finally, with some tropical species, it's possible to bend a culm in an existing clump of bamboo down to the ground, stake it and cover it partially with soil. Be sure to cover several of the nodes of the culm, as that's where it will form roots. Don't let the soil dry out completely.

According the Plants for a Future database, Fargesia nitida flowers are hermaphroditic, and are pollinated by wind.

I found some anecdotal information about propagating Fargesia nitida from seed on the University of British Columbia's garden forum, shown below: You can harvest the seed individually by hand. But it seems the best way to know that it is ripe is to allow it to fall to the ground, as they only fall when they are ripe. In order to not leave things to chance, it is recommended that a piece of cloth or a tarpaulin be placed on the ground, and the seed bearing culm be shaken. The best germination rate is when the seeds are sown fresh.

Season All Season
Date 2007-01-16
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Keywords: Rosa, Woody plant cuttings, Ornamental woody plants

PAL Question:

I am trying to grow roses from cuttings. They are sprouting little leaves but are still under empty soda containers for humidity. When I took a few out of the containers, they promptly shriveled up and died. Should I leave them for another month? I don't want to tug to see if they have roots, as that will disturb them. Do I apply foliar fertilizer?

View Answer:

I have listed a few useful webpages about propagating roses from cuttings below.

To answer your question about leaving them under cover, I think you probably should leave them for at least a brief while, given the very cold weather. I don't think you need to apply foliar fertilizer at this stage. The resources below should offer some additional advice on caring for your cuttings.

John Fisher's book, The Companion to Roses (Salem House Publishers, 1986), says that roses grown from cuttings may take longer to flower than those budded on rootstock, but (if they survive the process) they may live longer and will not sucker. Some roses are easier to propagate from cuttings, such as ramblers and Rosa rugosa, as well as some climbing roses and large-flowered roses.

According to Fisher, cuttings can be taken as early as August. You should choose young shoots with ripened wood that have borne flowers, and lateral shoots rather than leaders. He recommends selecting those shoots growing low on the shady side of the plant, and those with leaf joints that are close together. Make a clean cut just below a leaf joint. The cutting should be about 9 inches long with 2 leaf joints in the top 3 inches. Cut off the tip that has borne the flower and the leaf immediately underneath it. Remove leaves (but not buds) on the lower 2/3 of the cutting, since this is the part that will be planted in the ground. The soil should be a mix of loam and sand mixed down to a depth of about 9 inches, in a pot or V-shaped trench. Before planting the cutting, poke a hole in the soil for it to go into. Moisten the bottom end of the cutting with a cotton ball, and dip it in rooting hormone (or willow water). Put the cutting in the soil and press the soil around it firmly. If you need to protect it from frost, cover it with leaves or sacking during the winter. By summer, it should have formed a root, and should be ready to plant in the fall.

The information below may differ somewhat from these directions, but you may get a general sense of how your methods compare, and whether you want to try any of the methods suggested.

University of California Cooperative Extension
Morrison Gardens
The Southern Garden

Season All Season
Date 2007-01-16
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Keywords: Diospyros kaki

PAL Question:

When should Asian persimmons be harvested? Do they need to be fully colored and soft? I'd like to pick them before the crows and raccoons get them this year!

View Answer:

The answer to your question depends on whether you are growing an astringent or non-astringent variety of Asian persimmon. For example, Hachiya and Saijo are astringent, while Fuyu, Izu, and Jiro are non-astringent.

Asian persimmon (Diospyros kaki) can be picked when completely colored but still firm, as this link from University of California Master Gardeners of Napa County describes:
"When harvesting persimmons, allow the fruit to remain on the tree until it develops good color. Use pruning shears to cut the stem, leaving a short stem and the green calyx attached to the fruit. If the fruit is snapped off rather than clipped, the fruit may bruise.
"Astringent types such as 'Hachiya' can be left on the tree until they become soft-ripe, or you can harvest them when they have reached full color but are still firm. In that case, let them soften at room temperature before eating."

In your situation, I recommend not leaving the fruit on the tree to soften if you want to keep the critters from harvesting it!

The California Rare Fruit Growers website has a thorough guide to growing Asian persimmons.

Season Fall
Date 2014-08-27
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Keywords: Cold protection of plants, Frost, Camellia

PAL Question:

How can I protect my camellia shrubs from very low temperatures?

View Answer:

The website of the International Camellia Society has a discussion of camellias and their cold tolerance, indicating that most spring-blooming Camellia japonica and fall-blooming Camellia sasanqua cultivars will survive a Washington, D.C. winter (zone 7, compared to our zone 8), but there is some concern about extreme cold and drying winds, and sudden drops in temperature (see excerpt below on winter protection, from the University of Georgia Cooperative Extension Service):

Winter Protection

Covering a camellia plant provides frost protection but does little good in a severe freeze. If plants are covered with cloth, plastic or paper, prop up the cover so that it does not touch the buds. Put the cover on after the sun goes down and remove it before mid-morning the next day.

There are additional approaches to providing winter protection against plant damage. Maintain good soil moisture, especially just before freezes. Maintain adequate nutrition by following current fertilizer recommendations. Plant in locations that provide moderate winter shade. Select varieties with good winter hardiness.

The article below from the North Carolina State University Extension has a good general discussion of winter protection for evergreens such as camellias.

Season Winter
Date 2007-01-16
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Keywords: Recycling (Waste, etc.), Euphorbia

PAL Question:

I have a large Euphorbia trigona (also known as an African milk tree), nearly 7 feet tall that currently lives in my living room. I will be moving soon, and it is too large to take with me. I'm concerned about putting it in the yard waste bin and exposing the people who collect it to the irritating sap. Also, is this type of Euphorbia a noxious weed that I should keep out of the yard waste altogether?

View Answer:

I believe it should be fine to put the Euphorbia in your yard waste, as yard waste handlers wear gloves. You could minimize the amount of sap going into the recycling by cutting it into the largest allowable sections, then setting them on a tarp to ooze their sap for a while before adding them to the container. There are a few varieties of Euphorbia that are classified as noxious weeds and would need appropriate disposal, and your plant is not one of them.

Season All Season
Date 2007-01-16
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Keywords: Lilium (Lily family), Plants in winter, Bulbs

PAL Question:

I was recently given 6 Oriental lily (Lilium) bulbs - bare root. It seems much too cold (late February) to put these in the ground. They are currently naked in the garage, but would it be better to pot them until the ground is workable? I have not raised lilies before, other than daylilies.

View Answer:

Generally, it is good to plant bulbs soon after you get them, but if you need to wait (due to cold weather and unworkable soil), keep the bulbs somewhere cool, and keep them "in moist sand or peat moss until scales plump up and new roots begin to sprout" (Sunset Western Garden Book, edited by Kathleen Norris Brenzel, 2001).

The Gardener's Guide to Growing Lilies by Michael Jefferson-Brown and Harris Howland (Timber Press, 1995) confirms your thought that it is too cold to plant them out in the garden (I would wait until the threat of freezing temperatures subsides). According to the resource mentioned above, Oriental lilies will do very well in pots, so what you could do is pot them now, and if you decide you would like to move them into the garden when it warms up, you could either put them, pot and all, into the border, or gently remove them from the pot without too much root disturbance, and plant them in the soil.

Season Winter
Date 2007-01-16
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Keywords: Native plants--Washington, Green roofs (Gardening), Sedum

PAL Question:

I am trying to find a Sedum expert to help figure out better uses for this plant as a green roof material. Can you help point me in the right direction? Also, are there native Sedums?

View Answer:

Here is a list of the books the Miller Library has on this subject, including the following titles:

  1. Planting green roofs and living walls by Nigel Dunnett and Noel Kingsbury (Timber Press, 2004)
  2. Ecoroof: questions & answers by Portland Environmental Services (Portland, Or. : Environmental Services, 2004)
    Note: Portland's Ecoroof Program is a cooperative effort of the Bureau of Environmental Services and the Office of Sustainable Development. The program promotes ecoroofs by researching ecoroof technologies an providing information and technical assistance to community members.
  3. Green roofs: their existing status and potential for conserving biodiversity in urban areas by Ecoschemes Ltd (Peterborough: English Nature, 2003)

An article by Jessie Keith from The American Gardener (March/April 2005, pp. 38-41) mentions different types of Sedum appropriate for a green roof, which I will list here:

  • Sedum album 'Coral Carpet'
  • Sedum 'Green Spruce'
  • Sedum lydium
  • Sedum rupestre (syn. S. reflexum)
  • Sedum sexangulare
  • Sedum spurium 'John Creech'
  • Sedum telephium 'Matrona'

You might also want to speak with someone at the Cascade Cactus and Succulent Society of Washington State.

There are some Sedum species native to the Northwest.The Sedums that are native to the Pacific Northwest, according to The Encyclopedia of Northwest Native Plants for Gardens and Landscapes by Kathleen Robson, (Portland, OR: Timber Press, 2008)include:

  • Sedum divergens Cascade stonecrop
  • Sedum laxum Roseflower stonecrop
  • Sedum oreganum Oregon stonecrop
  • Sedum oregonense Creamy stonecrop
  • Sedum spathulifolium Broad-leaved stonecrop
  • Sedum stenopetalum Wormleaf or narrow-petaled stonecrop

Two additional species are listed in Plants of the Pacific Northwest Coast, edited by Jim Pojar and Andy MacKinnon (Richmond, WA: Lone Pine Publishing, 1994):

  • Sedum integrifolium Roseroot
  • Sedum lanceolatum Lance-leaved stonecrop

Season All Season
Date 2008-02-07
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Keywords: Bonsai

PAL Question:

I am looking for a class or program that shows how to grow bonsai trees.

View Answer:

The Pacific Northwest Bonsai Clubs Association has a list of bonsai instructors in our area.

Bonsai Northwest, 5021 S. 144th St., Tukwila has classes that cover outdoor repotting of bonsai.

Several local nurseries occasionally offer classes or presentations on bonsai, so it would be worthwhile to check the event listings on the Puget Sound Bonsai Association website.

Season All Season
Date 2007-01-18
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Keywords: University of Washington, Flowering cherries, Flowering trees, Prunus, Garden tours

PAL Question:

I would like to know when most of the beautiful flowering trees will be in bloom on the University of Washington campus this spring? I would like to bring a tour group to see them.

View Answer:

There is actually a "Tree Tour" of the University of Washington campus, called the C. Frank Brockman Memorial Campus Tree Tour, but it does not focus on flowering trees. I would recommend that you bring the group when the Yoshino cherry trees (Prunus x yedoensis) in the Quad are in bloom later this month (mid- to late-March). The Quad is also near the Grieg Garden, by Thompson Hall, which is an attractive spot.

Here is an excerpt from an article from the UW Alumni magazine about that garden:
"The Grieg Garden is the reverse of what folksinger Joni Mitchell once sang about they 'unpaved' a parking lot and put up Paradise. Until the renovation of the HUB [Husky Union Building] Yard in 1990, the space south of Thompson Hall was for cars. Today it is for people (and squirrels). One of the UW's newest beauty spots, the Grieg Garden is a cozy clearing surrounded by trees and flowering shrubs. Located on the north side of the HUB Yard, it is best in the spring, when rhododendrons and azaleas frame the space in drifts of lavender, crimson, magenta and pink."
-Tom Griffin

Season Spring
Date 2007-01-18
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Keywords: Rosa, Transplanting

PAL Question:

I have a rose bush in the back yard, under a tree, it seems to be thriving but no one can see it blooming. I want to move it to a more prominent place in our yard. What is the best time of year for transplanting this rose?

View Answer:

Moving your rose out from under the tree is probably a good idea. Roses: 1001 Gardening Questions Answered by the editors of Garden Way Publishing (1989), says that the best time to transplant it to its new location is early spring or late fall. Before moving it, prune it, leaving three to four canes. Prepare the new hole in the ground (and) give it some extra attention after it is planted. This resource says that spring transplanting is preferred, because with warm weather on the way, the rose will have a better chance of starting new growth. When digging up your rose, dig a circular trench one foot away from the crown of the plant, removing the soil around the plant with your shovel. Loosen the root ball, and then take hold of the crown and push it back and forth to loosen it. Then lift it out of the hole. Dig a deep hole in the new location. Add two inches of compost, build a mound of soil, and spread the roots over it. Fill in with topsoil, make a ridge of soil around the base of the plant, and water well. Afterwards, water carefully, neither too much nor too little.

Season All Season
Date 2008-01-24
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Keywords: Flowering cherries, Prunus

PAL Question:

I have an area in my garden where I would like to plant a cherry blossom (Prunus). However there are telephone and power wires above so I would like the tree to reach no more than 15 feet in maturity. Are there any dwarf or smaller growing varieties?

View Answer:

Here are two suggestions for smaller flowering cherry trees, from a list in Trees & Shrubs for Pacific Northwest Gardens (2nd ed.) by John A. Grant and Carol L. Grant (Timber Press, 1990):

  • Prunus serrulata 'Shogetsu' reaches 15 feet tall, by 22 feet wide.
  • Prunus x 'Hally Jolivette' reaches about 15 feet.
    Here is an article by Wayne Winterrowd in Horticulture Magazine (May 1, 2007) with additional information about this tree, which he refers to as the "loveliest of trees," and the best of the flowering cherries..
  • Season All Season
    Date 2007-01-18
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    Keywords: Rosa, Ornamental climbing plants, Disease-resistant plants, Organic gardening

    PAL Question:

    My neighbor wants a rose, but it will be planted in an organic garden. It is a sunny warm spot (for Seattle), but I think disease resistance is a must. What is a source for disease resistant roses for our climate? Also, does growing clematis on a climbing rose limit its disease resistance?

    View Answer:

    The reason that clematis and rose make good companions has to do with the rose providing the structure the clematis needs, and the pairing allowing for interesting combinations of color and shape, rather than one providing disease resistance to the other.

    Generally, the most disease-resistant roses are species roses, but there are additional choices.

    This article from Oregon State University Extension lists resistant roses and their other qualities (scent, repeat bloom, color).

    This article from Washington State University Extension is entitled "Disease-Resistant Roses for the Puget Sound Area."

    There are several excellent books on growing roses in our area:

    North Coast Roses : For the Maritime Northwest Gardener by Rhonda Massingham Hart (Seattle : Sasquatch Books, c1993)

    Jackson & Perkins Beautiful Roses Made Easy : Northwestern Edition by Teri Dunn & Ciscoe Morris. (Nashville, Tenn. : Cool Springs Press, 2004)

    Roses for the Pacific Northwest by Christine Allen (Vancouver : Steller Press, 1999)

    Roses for Washington and Oregon by Brad Jalbert, Laura Peters (Edmonton : Lone Pine Pub., 2003)

    Roses for the Inland Northwest. Washington State University Extension ; [Washington, D.C.] : U.S. Dept. of Agriculture, [2004])

    This book is a comprehensive guide to combining clematis and roses: The Rose and the Clematis As Good Companions by John Howells ; photographs by the author ; flower arrangements by Ola Howells (Woodbridge : Garden Art Press, 1996)

    All of these titles are available in the Miller Library.

    Season All Season
    Date 2007-02-10
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    Keywords: Snails, Slugs, Pesticides and the environment

    PAL Question:

    Is there any scientific reason to not use the iron phosphate based slug baits (Sluggo etc.) near bodies of water (streams, ponds, lakes)? I did some preliminary (not exhaustive) Google research and did not find anything to suggest they cause increased algae growth. Please let me know what you can find on this subject. Are other water-borne organisms harmed?

    View Answer:

    The Material Safety Data Sheet for Sluggo indicates that one should avoid disposal of this product near bodies of water (see Section 13), though there is not definitive information in Section 12 on the ecological impacts of the product on algae and other life forms. Here is a link to the PDF document.

    See also "Grow Smart" from King County Hazardous Waste Management on dealing with slugs in gardens.

    It does not list Sluggo, Escar-go, or any of the other iron phosphate products as water pollution hazards, but the MSDS sheet makes me think there is a potential problem with dumping large quantities. It seems not enough information is out there, perhaps because the research has not been done. Here is the page from the Pesticide Action Network database, where you can see that iron phosphate's eco-toxicity has not been established.

    Here is what the Environmental Protection Agency has to say about iron phosphate slug baits:

    Ecological Effects Hazard Assessment

    "A number of ecological effects toxicology data requirements were waived based on the known lack of toxicity of iron phosphate to birds, fish and non-target insects, its low solubility in water, conversion to less soluble form in the environment (soil), and its use pattern (soil application). An acute oral toxicity study in Bobwhite quail (NOEL & LD50 greater than 2000 mg/kg) indicated that iron phosphate was practically nontoxic to avian species. Based on these factors, the data requirements for the toxicity studies in Mallard duck, rainbow trout, freshwater invertebrates, and non-target insect/honeybees are waived. It is likely that there will be exposure to ground-feeding non-target insects and earthworms. Submitted studies involving ground beetles, rove beetles and earthworms demonstrated that the product will not affect these organisms at up to two times the maximum application rate.

    Environmental Fate and Ground Water Data

    Exposure assessments on this type of product (biochemical pesticide) are not performed unless human health or ecological effects issues arise in the toxicity studies for either of these disciplines. Since no endpoints of concern were identified, there is no requirement for environmental fate data.

    Ecological Exposure and Risk Characterization

    Exposure to daphnids and other aquatic invertebrates would not occur based on current label use directions. Exposure to honeybees is also not expected to occur, due to the composition and particle size of the end-use product and its use pattern (soil application). Non-target insects, such as ground beetles and earthworms, could encounter the end-use product; however, in tests of rove beetles, ground beetles and earthworms, no effects were observed at up to twice the maximum application rate. Thus, the acute risk to aquatic invertebrates, non-target insects, and earthworms is considered minimal to nonexistent."

    United Nations Environment Programme has information on the impact of Phosphorus on aquatic life, a process called eutrophication. However, the iron phosphate in Sluggo and similar products binds with Phosphorus, which may mitigate the effects in water.

    Season All Season
    Date 2008-02-07
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    Keywords: Hamamelis, Woody plant propagation

    PAL Question:

    Do you have any information on how to propagate vernal witch hazel?

    View Answer:

    To propagate vernal witch hazel (Hamamelis vernalis), Michael Dirr's Reference Manual of Woody Plant Propagation (Varsity Press, 1987) says the following:

    From seed:
    70% germination after 3 months cold stratification,
    75% after 3 warm months/3 cold,
    81% after 4 warm months/3 cold,
    85% after 5 warm/3 cold.
    Fall planting improves success.

    From cuttings:
    Easy to root and keep alive.

    Grafting is not used much as a propagation method.

    The American Horticultural Society's book, Plant Propagation (DK Publishing, 1999) says that softwood cuttings do not overwinter well. One should take early nodal stem-tip cuttings as soon as new growth in spring is 2 3/4 - 4 inches long. Provide bottom heat and rooting hormone to speed rooting in 6-8 weeks. Layering can also be done in spring. Grafting can be done in late summer.

    The following is from the Royal Horticultural Society:

    "To propagate by seed, harvest as soon as the fruits mature in late summer to early autumn and sow in a cold frame promptly before they have a chance to dry out. Fresh seeds may take up to 18 months to germinate. When the seedlings appear, prick them out and pot them up for overwintering in the greenhouse for their first year. They can be planted out late the following spring and will reach flowering size in about six years. Witch hazel suckers freely and also can be propagated by layering in early spring or autumn. Layering works well, but the process will take a year. Softwood cuttings can be rooted in the summer. Volunteer seedlings can also be potted up and transplanted."

    Season All Season
    Date 2007-02-21
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    Keywords: Styrax, Woody plant propagation

    PAL Question:

    Could you tell me how I would propagate Styrax?

    View Answer:

    All the propagation information I found in our reference books indicates that Styrax is best propagated by softwood cuttings in June to early July (cuttings are easy to root and overwinter easily), or by fresh seed as soon as ripe, kept at 50 degrees for 3 months and then moved to the refrigerator for 3 months.

    If you wish to try grafting Styrax, this link to general grafting information from North Carolina State University's Extension Service may be of use.

    Season All Season
    Date 2007-02-21
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    Keywords: Garden design, Children's gardens

    PAL Question:

    I am interested in information about gardening with children and gardens designed for children. Can you recommend some relevant web sites and articles?

    View Answer:

    Below are some useful web sites about children's gardens. They include actual children's garden web sites which may have garden maps or plans as well as information about how the garden was designed, and horticulture sites with information about gardening with children.

    The Edible Schoolyard Project

    Magnuson Park Children's Garden

    kinderGarden

    The Helen & Peter Bing Children's Garden

    Children's Garden at the Morton Arboretum

    The Midway Plaisance Children's Garden

    Ithaca Children's Garden

    Gardening With Children

    Each year, the National Children & Youth Garden Symposium, takes place at varying locations.

    You may wish to visit the Miller Library and search the Garden Literature Index, which has an article about past years' symposia (see abstract here: 2006 Youth Garden Symposium. Robbins, Heather American Gardener; Sep/Oct2006, Vol. 85 Issue 5, p12-15 The article presents the highlights of the 2006 annual American Horticultural Society's National Children & Youth Garden Symposium held in Saint Louis, Missouri. It cites the implications of the high number of participants in the event. The issues discussed at the educational sessions in the symposium include building children's gardens and community gardening. Attendees were given the opportunity to explore the Missouri Botanical Garden, the event's host garden.)

    Below is just a sampling of other articles from the "children's gardens" search results:

    1. Gardening on the curriculum? Why not? By: West, Cleve. Garden, Jan2007, Vol. 132 Issue 1, p13-13, 1/2p; (AN 23649207)

    2. Lewis Ginter Botanical Garden. By: Day, Susan. Birds & Blooms, Oct/Nov2006, Vol. 12 Issue 5, p54-55, 2p, 1 map, 4c; (AN 22575160)

    3. SCAPE'S GARDEN OF DISCOVERY. HD: Hospital Development, Mar2006, Vol. 37 Issue 3, p6-6, 1/4p; (AN 20303088)

    4. The Best Backyard In The World. By: McGuire, Leslie. Landscape Architect & Specifier News, Mar2006, Vol. 22 Issue 3, p58-65, 8p, 1 map, 8c; (AN 20532564)

    5. THE ACTIVITY MATRIX. Landscape Architect & Specifier News, Mar2006, Vol. 22 Issue 3, p60-63, 4p, 8c; (AN 20532565)

    6. Children's Garden Consultants: A New Model of Engaging Youth to Inform Garden Design and Programming. By: Lekies, Kristi S.; Eames-Sheavly, Marcia; Wong, Kimberly J.; Ceccarini, Anne. HortTechnology, Jan-Mar2006, Vol. 16 Issue 1, p139-142, 4p, 2 charts; (AN 20620955)

    7. Duke Garden. By: Stewart, Joann. Daylily Journal, Winter2005, Vol. 60 Issue 4, p414-415, 2p, 4c; (AN 19479979)

    8. Cultivating gardeners. By: Benson, Sally D.. American Nurseryman, 9/1/2005, Vol. 202 Issue 5, p4-4, 2/3p; (AN 18031480)

    9. Fall for Fun: New Children's Garden. By: Sherman, Marilyn. Chicagoland Gardening, Sep/Oct2005, Vol. 11 Issue 5, p78-79, 2p; (AN 18096223)

    10. Kid's paradise. By: Patrick, John. Gardening Australia, Apr2005, p22-26, 5p, 9c; (AN 16593169)

    There are also articles available in landscape architecture and urban planning publications which we do not have in our library, but which you might find at the University of Washington Libraries. I searched the Avery Index to Periodicals and came up with quite a few potentially useful results. Here are some examples:

    Child's play: the Ian Potter Foundation Children's Garden is a new component of the very successful observatory precinct at the Royal Botanic Gardens Melbourne [Australia] / Bruce Echberg. :photos., site plans. Landscape architecture Australia 2006 Nov., n.112, p. 49-52, ISSN 1833-4814.

    Footprints of school gardens in Sweden / Petter kerblom. photos., drawings, plans, site plans. Garden history 2004 Winter, v.32, n.2, p.[229]-247, ISSN 0307-1243.

    We also have many books available here at the Miller Library on gardens for children.

    Season All Season
    Date 2007-02-20
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    Keywords: Paeonia

    PAL Question:

    I have a peony that failed to flower this year. What could be the cause of this?

    View Answer:

    Cindy Haynes of Iowa State University of Extension has a helpful list of possible reasons peonies may fail to flower. If there are no buds, it may be due to: not enough sun; recently transplanted; planted too deeply; too much fertilizer; need to be divided (clumps too big); plants immature; premature removal of foliage (in July or August). If they have buds that don't open, these may be the reasons: late freeze; other extreme weather; fungal diseases; insects; undernourished./p>

    Another similar list of causes, from Ohio State University Extension:

    planting too deeply
    immature plants
    excess nitrogen
    inadequate sunlight
    overcrowding
    phosphorus and/or potassium deficiency
    insect or disease problems
    competition from roots of nearby plants
    late freezes

    Season All Season
    Date 2007-02-20
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    Keywords: Tree roots, Conifers

    PAL Question:

    Can you suggest any larger growing conifers (ex. Lawson's cypress) whose root systems are not invasive? The area I'm interested in planting is near water lines.

    View Answer:

    There are a number of conifers listed on the locally developed web pages of Great Plant Picks.

    I would suggest looking at some of these, and then checking the web page of SelecTree, where you can select trees for low root damage potential.

    For instance, if you are interested in planting a fir tree such as Abies grandis or Abies pinsapo, you would find out from SelecTree's full tree record that both of these have moderate root damage potential. Calocedrus, Picea orientalis, Sequoiadendron and Cryptomeria are also rated as moderate. Cephalotaxus fortunei is rated low, as are Pseudotsuga menziesii, and several Chamaecyparis species. The following conifers rated as having high root damage potential:

    Picea abies NORWAY SPRUCE

    Picea brewerana BREWER'S WEEPING SPRUCE

    Pinus cembra SWISS STONE PINE

    Pinus nigra caramanica CRIMEAN PINE

    Pinus taeda LOBLOLLY PINE

    Season All Season
    Date 2007-01-25
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    Keywords: Phalaenopsis, Orchidaceae (Orchid family)

    PAL Question:

    I have a question about a Phalaenopsis orchid. The orchid is a year old and at the top of last year's flower stalk has grown a new set of leaves as well as roots. Can this be cut off and re-rooted? Also, after the blooms fade, do you cut the stalk off and if so, how far?

    View Answer:

    Here is some information on propagation Phalaenopsis, from a commercial orchid grower:

    "Phalaenopsis can be vegetatively propagated by cutting the flowering stem above a stem internode, the dormant growth 'eye' is covered with a triangular sheath. Cut, with a hot knife or shears, through the flower stem after the last flower has fallen. Then move the plant to a dimmer area. In most cases, new plants will start from the dormant 'eyes.' After the new plants initiate, the mother and 'keikis' (babies) can be move gradually back to higher light. When the keikis have 2-3 roots, the keikis can be removed, by slicing between the stem and the keiki, or cutting the stem above and below keiki's attachment point. The new plant can now be potted up and grown on. If more flowers are desired, cut the stem as above, but do not move the plant. In the second method, the mother plant is topped. As a monopodial plant, Phals continue to grow vertically. In time, they discard their lower leaves. The leaves have served as a storage vessel of water and nutrients. The leaves have outlived their usefulness and are discarded. New roots are produced above the leafless stem, as the Phal continues growing vertically. The stem can be cut below the new roots. The top part, with leaves and roots, can be repotted after proper care of the cut. The remaining stub can be left as is, for a few days/weeks. Soon, new little plants will be found growing out of the old stub. These keikis can be repotted in the same manner as the first method. They will grow on and eventually bloom. If left on the stub, they will often bloom sooner, than if individually potted."

    The American Orchid Society has a video illustrating the potting of a keiki, as well as a host of other orchid care information.

    You may find the following links to the Brooklyn Botanic Garden useful for general directions on orchid care. Here is an excerpt: "Some species will also produce plantlets on the flowering spikes, complete with leaves and roots. These small offshoots can be pruned and planted, but keep in mind that transition from plantlet to flowering specimen is a long process requiring several years and lots of patience." Here is another helpful link from the Brooklyn Botanic Garden website.

    As for what to do with a spent flower stalk, here is what the Royal Horticultural Society recommends: "A flower spike can continue to bloom for up to three months. Once faded, cut the spike just above the second node (joint) beneath the spent flowers, and a flowering sideshoot may develop."

    Season All Season
    Date 2007-01-24
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    Keywords: Hardy plants

    PAL Question:

    When a plant is assigned a zone or temperature tolerance, is it the actual temperature of the air or is wind chill temperature counted? In other words, if I have a plant that tolerates temps to 20 degrees and the temp today is 28, but the wind chill is 15, is my plant still hardy?

    View Answer:

    Here is a link to the frost zone map for the U.S.

    Apparently, wind chill does not affect deciduous plants. If your evergreen plants are sheltered from the effects of the wind, then they may be protected from moisture loss. Below is additional information about plants and wind chill.

    From Portland, OR area garden writer Ketzel Levine:

    "Wind chill has little effect on deciduous plants, so if we're talking forsythia and blueberry, it's not an issue. Of course it does becomes an issue if the subject is broadleaf evergreens (boxwood, hollies, osmanthus, etc.) and to a lesser degree, needled evergreens. Sub-freezing winds rob leaves of moisture, a serious problem if a plant continues to photosynthesize through winter. But the USDA zones do not take wind chill into consideration, and if I were you, I wouldn't either. If you're not a risk taker, stick with Z6 plants; otherwise, let the cold winds blow."

    From Rob Gough, Montana State University Extension agent:

    "Do plants feel wind chill like we do? It sure feels a lot colder to us when the wind is blowing. It makes 30° feel like 0°. Meteorologists express this feeling by the term 'wind chill' and we often hear wind chill advisories on the local radio station. Do plants feel wind chill? Does a wind chill of 25° below make the plant react as though it were that cold?

    The answer is in the word 'feel.' The term 'wind chill' was developed to express how the combination of wind speed and temperature 'feel' on exposed skin. The skin has nerves which transmit that feeling to the brain and we say, 'Boy, it sure feels a lot colder than 30 degrees with all this wind.' But the plant doesn't feel. It has no nerves to transmit that impulse. So to use the term 'wind chill' in relation to plants is meaningless. But that's not to say that wind and cold do not affect plants. Last time I told you how cold influences plants. Wind plays an important role too. Wind can increase the evaporation of soil moisture, thus speeding drying and making water harder for the plant to come by. Wind also speeds evaporation of moisture from the plant surface. Even without leaves, deciduous plants can lose moisture through their young bark. The faster the wind, the faster moisture is lost.

    You may notice the windward side of your evergreens are scorched, or burned. The needles are brown or reddish on that side. That's windburn and it's simply desiccation of tissue caused by the wind. Again, like cold damage, wind damage is also the result of drying out of the tissues. If you want to know more about winter damage, contact your county extension office."

    Season Winter
    Date 2007-01-12
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    Keywords: Landscaping drain fields

    PAL Question:

    I know ornamental grasses are generally okay to plant on drain fields, but does this include larger grasses such as pampas grass? How about larger Miscanthuses? Arundo donax? There are mature pampas grasses already planted on the site I'm planning for. I'm wondering if they should really "go," and if so, is there something else that would give some height in this area without impacting the drain field.

    View Answer:

    Here is a link to the Miller Library's Gardening Answers on planting ornamental grasses in drain fields.

    Here is the relevant section:

    Grass is the ideal cover for drain fields. Grasses can be ornamental, mowed in a traditional lawn, or left as an unmowed meadow. You can also try groundcovers and ferns. The key to planting over the drain field is to select shallow-rooted, low-maintenance, low-water-use plants. When tank covers are buried, keep in mind that plantings over the tank--from inlet to outlet--will have to be removed every three or four years for inspection and pumping.

    Planting your drain field will be much different from other experiences you may have had landscaping. First, it is unwise to work the soil, which means no rototilling. Parts of the system may be only six inches under the surface. Adding 2 to 3 inches of topsoil should be fine, but more could be a problem. Second, the plants need to be relatively low-maintenance and low-water use. You will be best off if you select plants for your drain field that, once established, will not require routine watering.

    SOURCE: WSU Cooperative Extension - Clallam County

    Thurston County, Washington, has some information about landscaping a drain field, including plant suggestion.

    Additionally, the Pacific Northwest Gardener's Book of Lists (1997, by R. & J. McNeilan) offers a number of groundcover lists for various situations, including groundcovers for dry sites, slopes, and sun and shade. The Miller Library has this book.

    Here is an article from King County.

    I would be concerned that the larger Miscanthus plants might develop massive root systems which go far too deep for the site's needs. Also, Arundo donax is an invasive plant, so you should not use it in your landscape. The Washington Noxious Weed Control Board has further information on this plant.

    You may wish to remove the Pampas grass (Cortaderia) as well, as it is potentially invasive, has a deep root system, and is a prolific reseeder.

    Season All Season
    Date 2007-04-10
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    Keywords: bats, Quirky, Attracting wildlife

    PAL Question:

    I have a couple of questions. Are there plants I can grow that will attract bats, and are there plants that are bat-like in appearance?

    View Answer:

    The organization Bats Northwest recommends providing habitat (such as hollow trees and snags). The Washington Department of Fish and Wildlife has information on bat houses you can build or purchase. More information can be found at Bat Conservation International.

    I did not find specific lists of bat-attracting plants, but providing a diverse tree canopy which includes trees that attract moths (for bats to eat) may make your landscape more bat-friendly. The British Bat Conservation Trust suggests that you leave some wild areas in the garden, add a pond if you can (as a place for bats to drink and forage on insects and their larvae), and plant night-scented flowers. Plant diversity seems to be the key: you can try growing flowers of different shapes, sizes, and fragrances, pale single flowers, and flowers which are good "landing platforms" for insects (such as daisy and carrot family plants).

    There are several plants that resemble bats. Here are a few suggestions:

    Season All Season
    Date 2014-10-08
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    Keywords: Glyceria, Muhlenbergia, Holodiscus discolor, Elymus mollis, Symphoricarpos albus, Rosa nutkana, Vaccinium ovatum, Mahonia aquifolium, Festuca, Seaside gardening, Gaultheria shallon

    PAL Question:

    Do you have some suggestions for hardy, lower growing plants that would do well near the water? Our house is on the south side of Whidbey Island. The main plantings will be behind the house, thus roughly 75-100 yards from the shore. This part of the yard has early morning sun and then some shade in the afternoon. And, since we have a large yard at home we are working toward very low maintenance at the beach.

    View Answer:

    The following plants are mentioned in April Pettinger's book, Native Plants in the Coastal Garden (Whitecap, 2002):

    SHRUBS

    Arctostaphylos uva-ursi (Kinnikinnick)
    Gaultheria shallon (Salal)
    Vaccinium ovatum (Evergreen huckleberry)
    Rosa nutkana (Nootka rose)
    Holodiscus discolor (Oceanspray)
    Symphoricarpos albus (Snowberry)
    Mahonia aquifolium (Oregon grape)

    NATIVE GRASSES

    Festuca idahoensis (Idaho fescue)
    Festuca idahoensis spp. roemeri (Roemer's fescue)
    Leymus mollis or Elymus mollis (Dunegrass)
    Deschampsia cespitosa (Tufted hairgrass)
    Festuca rubra (Red fescue)
    Glyceria grandis (Reed mannagrass)
    Muhlenbergia glomerata (Marsh muhly)

    There are many other ideas in this book, which I highly recommend.

    Season All Season
    Date 2007-03-02
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    Keywords: Ficus benjamina

    PAL Question:

    Some of the leaves on my ficus plant have turned yellow and dropped. What could be the cause of this, and what should I do to remedy it?

    View Answer:

    There are a number of things which might cause your Ficus leaves to turn yellow and drop. Here is what the book, The House Plant Expert by D. G. Hessayon (Expert Books, 2001) says about Ficus troubles:

    A sudden loss of leaves is usually the result of overwatering. Other possibilities are low winter temperatures, low winter light, too much fertilizer, and cold draughts.

    Yellowing leaf edges and some loss of lower leaves can be a sign of underfeeding. Feed during the growing season.

    The author does not recommend frequent repotting, but suggests doing this in spring every 2 years until the plant is too big to move easily.

    If your fig is a weeping fig (Ficus benjamina), the shedding of leaves is an annual (fall) occurrence, and not necessarily a sign of problems, according to The Complete Houseplant Survival Manual by Barbara Pleasant (Storey, 2005).

    Season All Season
    Date 2008-02-07
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    Keywords: Plant diseases, Phytophthora

    PAL Question:

    Will the heavier than normal rainfall this fall and winter create an increased problem with Phytophthora this year? Is there anything we can do now or in the Spring to prevent a Phytophthora problem? Is there a chemical we should spray, and when?

    We have numerous Rhododendrons, Azaleas, Heather, Camellias, etc. There are areas of our gardens where puddles have formed during, and remain for the day after, heavy rains. Some areas probably have a clay lens of soil underneath that is preventing good drainage, and others may have a mass of roots preventing the good drainage.

    We've had Phytophthora before in two groupings of Rhododendrons (2 different varieties). We removed those plants, drenched the soil with the recommended chemical, waited a year, then replanted the same varieties as before. It seemed that things have been fine for at least the past five years, but now, seeing puddles, I'm concerned. Suggestions?

    View Answer:

    Phytophthora is a fungus which favors our cool, wet conditions and also tolerates heat and drought, so you may be correct that the heavy rainfall will intensify the problem. Here is a link to a September 2011 article from the journal Digger by Niklaus Grunwald, which discusses the origins and spread of the disease.

    Here are some links to PDF documents with further information:

    Oregon State University information about Phytophthora ramorum (sudden oak death) for forest managers and nursery operators

    Washington Toxics Coalition information on Phytophthora root disease

    You can ask when buying plants from local nurseries if their stock has any known problems with this fungus, and you can avoid purchasing affected stock, or planting especially susceptible host plants. If you have walked in an area where the disease is present, clean your shoes before walking in unaffected areas.

    The Pacific Northwest Landscape Integrated Pest Management Manual published by Washington State University Extension (3rd ed., 2002) recommends the following methods of managing the root-rot (rather than leaf damage) manifestation of Phytophthora in Rhododendrons and Azaleas (your message does not indicate how your plants were affected by Phytophthora).

    1. Plant resistant species and hybrids.
    2. Avoid drought stress or flooding, high salinity, or poor drainage. The drainage issue sounds like one you should address in your garden.
    3. Remove and destroy diseased plants.
    4. Use clean water low in salts, and avoid splashing soil on plants when watering.

    More information, from University of California, Davis's Integrated Pest Management web site, indicates that the best way to prevent the disease is to provide good drainage and practice good water management. Here is more information from U.C. Davis.

    Season All Season
    Date 2008-02-07
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    Keywords: Narcissus

    PAL Question:

    I have heard that alcohol can be used to keep paperwhites from flopping over. Is there any truth to this? How is it administered?

    View Answer:

    Cornell University has a publication entitled "Pickling Your Paperwhites," by William Miller. Here is an excerpt:
    "Recent research conducted by the Flowerbulb Research Program at Cornell University has found a simple and effective way to reduce stem and leaf growth of paperwhites. The 'secret' is using dilute solutions of alcohol. Properly used, the result is paperwhites that are 1/3 to 1/2 shorter, with equal sized flowers that last as long as normal.We suggest planting your paperwhite bulbs in stones, gravel, marbles, glass beads, etc. as usual. Add water as you normally would, then wait about 1 week until roots are growing, and the shoot is green and growing about 1-2" above the top of the bulb. At this point, pour off the water and replace it with a solution of 4 to 6% alcohol, made from just about any 'hard' liquor. You can do the calculations to figure the dilution, but, as an example, to get a 5% solution from a 40% distilled spirit (e.g., gin, vodka, whiskey, rum, tequila), you add 1 part of the booze to 7 parts of water. This is an 8-fold dilution yielding 5% alcohol."

    Season All Season
    Date 2006-12-07
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    Keywords: Rosa

    PAL Question:

    I am using a Grandiflora rose named Prominent (Kordes) as a foreground planting; a climber (Autumn Sunset) is in the background. I love the color and the shape of Prominent's blooms, but the blooms are sparse and plants are spindly compared to the healthy climber. Is there anything wrong with planting a new Prominent bush a few inches from each existing bush, to create fuller looking plants?

    View Answer:

    Below are some general guidelines on spacing for roses. Since you are planting a Grandiflora near a climbing rose which I am assuming has a structure to climb, you could probably get away with planting a bit closer than the 30"-36" spacing recommended between two Grandifloras, but if you plant right up against the other rose, I imagine it would be problematic due to inadequate air circulation, which could lead to diseases. Here is what a publication of the University of Illinois Extension has to say:

    "A general rule of thumb suggests that roses should be planted about 24 inches apart. This spacing will vary depending on the type of rose you are planting. Old garden roses will need wider spacing, while miniatures can be planted closer. Sufficient space between plants allows for good air circulation, an excellent first step in disease control."

    Suggested Spacing for Roses, from Jackson and Perkins:

    Hybrid Teas & Grandifloras
    Space: 30" -36" apart
    Coverage: 6 -10 sq. ft.

    Floribunda
    Space: 24" -30" apart
    Coverage: 4 -6 sq. ft.

    English Rose
    Space: 36" apart
    Coverage: 10 sq. ft.

    Climber
    Space: 4' -5' apart
    Coverage: 12 -15 sq. ft.

    Hedge
    Space: 24" apart
    Coverage: 4 sq. ft.

    Shrub
    Large
    Space: 30" -36" apart
    Coverage: 6 -10 sq. ft.

    Small
    Space: 24" -30" apart
    Coverage: 4 -6 sq. ft.

    Miniature
    Space: 12" -18" apart
    Coverage: 1 -2 sq. ft.

    Tree Rose
    Standard
    Space: 3' -5' apart
    Coverage: 10 -15 sq. ft.

    Patio
    Space: 3' -4' apart
    Coverage: 10 -12 sq. ft.

    Miniature
    Space: 2.5' -3.5' apart
    Coverage: 6 -11 sq. ft.

    Season All Season
    Date 2007-03-09
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    Keywords: Recycling (Waste, etc.)

    PAL Question:

    Do you know of a source in the greater Seattle area or North Puget Sound that will take and recycle 1 gallon black plastic pots that nursery stock comes in?

    View Answer:

    If you have recycling service in the city of Seattle, you may put clean plastic plant pots in your recycling bin. If you do not have access to recycling, here are some other options. Seattle Public Utilities provides a list of places to recycle plastic pots. Flower World Nursery in Maltby also accepts plastic pots for recycling and reuse.

    Regular Hours:
    9:00am - 5:00pm, 7 days per week
    Phone: (425) 481-7565 or (360) 668-9575

    You may also call the following nurseries to find out if they are currently accepting 1 gallon plastic pots:

    Hayes Nursery
    Phone: (425) 391-4166
    12504 Issaquah-Hobart Road SE
    Issaquah, WA 98027

    The Copper Vine
    1315 E. Pine
    Seattle, WA 98122
    (206) 323 -0770

    Squak Mountain Nursery
    7600 Renton-Issaquah Rd SE
    Issaquah, Washington 98027
    (425) 392-1025

    You can also contact King County Solid Waste.


    Another exchange and recycling resource is
    Garden Web's Pacific Northwest Garden Exchange.

    Season All Season
    Date 2007-05-08
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    Keywords: Poisonous plants, Animals

    PAL Question:

    Could you recommend some good references with information about plants that are toxic to livestock, particularly to horses?

    View Answer:

    There are a number of resources which list plants that are toxic to animals, and specifically to horses. As you check the lists, keep in mind that just because a plant is not on the toxic list, one cannot assume it is non-toxic.

    Here are links to some useful lists:

    ASPCA Lists of Plants:

    Nontoxic to Animals

    Toxic to Horses

    Cornell University Department of Animal Science: Plants Poisonous to Livestock (search by affected animal species)

    Western Washington plants toxic to horses, from Oregon State University (includes probable toxic dose, toxin, symptoms)

    Dr. Duke's Phytochemical and Ethnobotanical Databases, from Agricultural Research Service: try searching by plant name. Highly technical, but shows what the active chemical properties are in various plants.

    Reprint from Trailblazers magazine

    Samuel Roberts Noble Foundation - Horse forage

    Ten most poisonous plants affecting horses, from the editors of Equus magazine

    The Miller Library also has the booklet entitled Commonly Cultivated and Native Oregon Plants Toxic to Domesticated Animals by La Rea Dennis et al., Pacific Western Research, 1990. It is organized by plant family, not by affected animals.

    Season All Season
    Date 2008-02-07
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    Keywords: Camellia sinensis, Aspalathus, Cyclopia, Citrus

    PAL Question:

    I am interested in growing tea plants. In particular, I am interested in these: Cyclopia intermedia (honeybush), Aspalathus linearis (rooibos), and Citrus aurantium (bergamot). Also, do you know which local nurseries might sell these plants?

    View Answer:

    For the first two plants, I consulted Cape Plants by Peter Goldblatt and John Manning (Missouri Botanical Garden, 2000). Cyclopia intermedia and other Cyclopia species (Honeybush) grow in southeast and southwest Africa in what is called "mountain fynbos" regions. The climate is similar to that of Mediterranean areas, so if your climate has wet winters and dry summers, there is a chance you may be able to grow this plant. The South African Honeybush Tea Association has more information about this plant as a source of tea.

    Aspalathus linearis, or Rooibos, is found in South Africa from the Bokkeveld Mountains to the Cape Peninsula. The website PlantzAfrica has information about it that suggests it is not often grown in home gardens: "This is thought to be due to the difficulty in propagation by seed or root cuttings and in providing the optimal growing conditions for the plants. In order to grow Aspalathus linearis successfully, seeds must first be scarified and then planted in acid, sandy soils." The Plants for a Future Database suggests that this plant would not grow with much success in a colder, wet winter climate.

    The bergamot which is used to flavor Earl Grey tea goes by the botanical names Citrus aurantium, C. aurantium subspecies or variety bergamia, and Citrus bergamia. According to Purdue University's New Crops web page, this tree is a native of Southeast Asia: "The sour orange flourishes in subtropical, near-tropical climates, yet it can stand several degrees of frost for short periods. Generally it has considerable tolerance of adverse conditions. But the Bergamot orange is very sensitive to wind and extremes of drought or moisture." See also the following from University of California, Riverside's Citrus Variety pages. The tree grows well in Italy and North Africa, but it may not do very well in the Pacific Northwest.

    Of these three plants, the only one for which I found a nursery source (in California, not locally) on Plant Information Online was the bergamot Citrus. You may want to call your favorite local nurseries to ask if they ever carry this plant, but I suspect that most will not, as it is not likely to succeed in our climate. You might have better luck growing familiar herbs like chamomile and mint which can be used for tea. You could also make green, black, and oolong tea from the leaves of Camellia sinensis, a plant which will thrive here in Seattle, and should not be too difficult to find. According to Keith Possee, who manages the UW Medicinal Herb Garden, offers the following advice:
    "The trick is to pick only two leaves and a bud in the spring flush of growth. If we lived in the tropics, home tea growers could be picking tea most or all of the year, but 48 degrees north latitude is not ideal." The most important step to learn is how to roll the leaves. Keith recommends this University of Hawaii Extension document entitled Home-Processing Black and Green Tea by Dwight Sato, et al.

    Season All Season
    Date 2008-02-07
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    Keywords: Vaccinium, Organic fertilizers, Fertilizers

    PAL Question:

    Is ammonium sulfate considered an organic fertilizer? I'd like to use some on my blueberries, but suspect it is not organic.

    View Answer:

    According to Fertilizers and Soil Amendments by Roy Hunter Follett (and others), ammonium sulfate is one of the oldest chemical fertilizers, and is "a frequent by-product of the steel industry, particularly the coking of coal." That doesn't sound like it meets organic guidelines. It is also tricky to use because it can cause phosphorus and aluminum to build up in the soil. The Organic Materials Review Institute lists it as a prohibited (for certified organic growers) synthetic crop fertilizer and soil amendment. You might do better using a slow-release certified organic fertilizer labeled for acid-loving plants. Cornell University Extension's publication, 2014 Production Guide for Organic Blueberries" mentions fish, soy, and alfalfa meal as organic-acceptable amendments.

    Season All Season
    Date 2011-04-01
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    Keywords: Asparagus, Propagation

    PAL Question:

    I planted young asparagus plants a couple of springs ago. This past fall, one of the plants produced fruits (small red balls like I've seen on Asparagus sprengeri.) I looked in my Hartman and Kester, but it did not mention means of using asparagus seeds to make more plants. Can this be done? If I left them on the plant outside all winter, are they still viable?

    View Answer:

    According to Franklin Herm Fitz in A Gardener's Guide to Propagating Food Plants, it is possible to grow asparagus from seed, but possibly not if the seeds have been out in freezing weather:
    "Collect the red berries from two-year-old or older female plants, harvesting before the first frost. Crush the berries and separate the seeds by hand (the seeds are large, shiny, and black) or by immersing them in water. The pulp will float as the seeds sink. Dry the seeds for 2 to 3 weeks. In the spring grow the new plants in deep, loose soil. After one season transplant them to a permanent bed (...) in early spring before growth resumes or in the fall after growth has ceased."

    Alternatively, as you probably know, asparagus roots may be divided and replanted, with the knowledge that each smaller root will take a year to become established so that it can produce a good crop.

    Season All Season
    Date 2010-02-25
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    Keywords: Noise pollution, Bamboo

    PAL Question:

    Could you recommend some plants that would be effective at screening out noise from a nearby, busy street? Would bamboo be effective? Any other suggestions?

    View Answer:

    I have some suggestions for planting and otherwise screening your property from the busy street adjacent to your house. I've started with an article from the Washington Post (linked below) that provides good food for thought about this problem. After providing some related information that you may not have considered (#1), I've given you a list of plants, most of which are native (#2). Since you have a relatively small area, you will have to plan carefully.

    Here is the link to the article from the Washington Post.

    1. My research indicates that a fence or other solid barrier--massive and thick, such as a brick wall or a berm--provides a more effective barrier to sound than a planting screen.

    University of British Columbia Botanical Garden Forums has a discussion on this topic, including this citation:
    From the book Arboriculture, third edition, Harris et al., page 138, figure 5-8 caption:
    "Thirty meters of trees and shrubs reduce truck noise about as effectively as a similiar area of bare cultivated ground. A berm, slope or solid barrier with woody plants would be more effective in absorbing noise (Cook and Van Haverbeke 1971)."

    2. You may decide to mask the sound. In addition to music, chimes, and the sound of water in a fountain, you might consider trees that rustle in the wind. You mentioned bamboo, and given your small space, I would recommend a clumping rather than a running bamboo. The frequently asked questions section of the American Bamboo Society website has information about choosing and growing bamboo. Unfortunately, the clumping types prefer sheltered spots and/or shade. You might consider planting some evergreen trees or shrubs on the edge of the property to shade the bamboo, which could be planted closer to the house (and the rustling sound would be closer to the windows). Or you could plant a running type of bamboo (some can take full sun) in a container or using a barrier.

    Evergreen trees and shrubs will provide the most effective barrier. Trees such as members of the Thuja genus in combination with a fence may be a place to start, but for more interesting ideas, try visiting the Great Plant Picks website. You can search with the word 'hedge' and come up with a good list of plants that will do well in the Pacific Northwest.

    Season All Season
    Date 2006-11-07
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    Keywords: Musa

    PAL Question:

    I have a bunch of banana trees in a greenhouse that are turning brown. Some are totally brown and others are turning brown at the ends of the leaves. The trees are about 10 feet tall. Any idea why they are turning brown and what can I do to fix them?

    View Answer:

    Are you growing Musa basjoo, Musa ensete, or another species of banana? Also, I wonder if your greenhouse is heated or not. Here is a link to comments on growing Musa basjoo outdoors in the Northwest on the University of British Columbia Botanical Garden Forums.

    According to this site, leaves which have browned from the cold can simply be removed in the spring. Here is a link to another discussion of browned banana leaves, from GardenWeb's Forum.

    Since your plants are under cover, there are probably different issues to consider, such as the humidity and temperature level in the greenhouse, and the amount of water the trees receive. They need to be kept moist but not waterlogged. Here is a link to general cultural information from California Rare Fruit Growers.

    According to the book, Exotic Gardening in Cool Climates by Myles Challis (Fourth Estate, 1994), Musa ensete is best overwintered in a greenhouse. It needs a large amount of water during the growing season to match the evaporation from its huge leaves, and it is a heavy feeder. Musa basjoo is the more 'hardy' banana. Here is what the Royal Horticultural Society says about overwintering Musa ensete, or Ensete:

    "To overwinter Ensete, our glasshouse is kept at 16C (61F) by day and 12C (53F) at night - at lower temperatures, lifted plants are prone to rotting. The lower the overwintering temperature, the earlier Ensete should be lifted and established in their winter containers, and the drier they should be kept subsequently. If only frost-free winter quarters are available, permanent container culture may be wiser. Musa species and cultivars are more forgiving of this operation, and can even be stored in a shed or garage."

    If you do not think that cultural conditions are the cause of the problem, you might look at this description of a disease affecting bananas.

    Purdue University's New Crop page has some information about diseases of banana.

    You might also bring sample leaves to a Master Gardener Clinic if you suspect a disease is causing the leaf problems.

    Season All Season
    Date 2007-03-14
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    Keywords: Hemerocallis, Container gardening

    PAL Question:

    We have the 'Stella d'Oro' daylilies, the Hyper Yellow variety. They are 9 years old now, going on 10. We divided them last year, and only had a couple of lilies. Where they are planted I don't believe they have enough sun. When we divided them, instead of 2 plants, we now have 7. I have a huge planter, on a wheelbase, and was thinking of putting 3 of them in it, perhaps 4. They would be located on the sunny part of our deck, which I know would be much better for them. What can you tell me about daylilies planted in containers? The pot is so big, you could grow a tree in it!

    View Answer:

    Planting your daylilies in a large container should be fine. Here is some general information from University of Georgia Cooperative Extension on growing daylilies, in which they suggest growing repeat-blooming daylilies in your containers. In general, smaller cultivars would be good choices for containers.

    If you keep them in the pot over the winter, you may want to protect them by covering with a thick mulch.

    You may wish to consult the frequently asked questions page on the American Hemerocallis Society website, which includes cultural information, such as the best place to plant daylilies, excerpted here:

    "You need to consider four things in determining where to plant your daylilies:

    Sun or Shade

    • Most daylilies do best in full sun. They will tolerate part-shade conditions, but require a minimum of six hours of direct sun per day.
    • Light yellow cultivars, many shades of pink, and delicate pastels need full sun to bring out their lovely colorings.
    • Many red and purple cultivars benefit from partial shade in the hottest part of the day because dark colors absorb heat and do not withstand the sun as well as lighter colors.

    Type of Soil

    • Any good garden soil is appropriate for growing daylilies. Daylilies will grow, however, in sandy soil or in heavy clay.
    • If you have heavy clay soil, add compost, humus, peat moss, and sand to make it more friable.
    • If you have sandy soil, add compost, humus, and peat moss to lesson its porosity and to increase water retention.

    Drainage

    • For maximum performance, daylilies should be planted in well-drained soil. One method of achieving adequate drainage in problem areas is to prepare raised beds, 3 to 6 inches above ground level."

    Season All Season
    Date 2007-11-09
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    Keywords: Iris

    PAL Question:

    I am looking for information on a Iris sibirica 'Mantra.' I want to know what it looks like, what its cultural requirements are etc. If you can find an image, that would be awesome.

    View Answer:

    The iris you mention is actually not a Siberian iris. Here is a photo from the Miller Garden website's alpine collection which lists this as a Pacific Coast iris, rather than Iris sibirica. This iris won an award of merit from the Pacific Coast Iris Society in 2000. Here is general cultural information from the King County Iris Society.

    Pacific Coast Native Iris (PCN), or Californicae (CA), are much sought after in the Pacific Northwest as our climatic conditions are ideal for them. Their graceful and dainty flowers bloom April to June on stems 1' to 2' tall, in a wide variety of striking colors and patterns. These irises thrive in the marine coastal climate, with dry summers and cool, wet winters. Plants are very prolific and grow readily from seed. Transplanting, however, can be difficult. They are best moved or divided in the early fall, when root growth is active and can continue well into winter. Plants can also be moved prior to spring bloom.

    Transplants must be kept well-watered until natural rainfall can maintain high soil moisture. They should be heavily mulched with bark dust, pine needles or leaves, to prevent frost damage to newly developing roots. Once established, plants are usually tolerant of normal freezes and periods of drought. If frost damage occurs to leaves, wait until well into spring to watch for signs of new growth. PCNs should receive at least a half a day of sunshine.

    Season All Season
    Date 2008-02-07
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    Keywords: Limonium, Helichrysum, Skimmia, Elaeagnus, Echinops, Alstroemeria, Callicarpa, Calluna, Aster, Lavandula, Achillea, Quercus, Viburnum, Dahlia, Cotoneaster, Acer

    PAL Question:

    My son and his sweetheart are planning a wedding in Seattle (my hometown) this coming September and would love to use seasonal flowers and greenery. I have not lived in the area for many years and am at a loss. Can you give us some suggestions please?

    View Answer:

    Here are some of the plants which are available in September: Achillea (Yarrow)
    Alstroemeria (Peruvian lily)
    Aster
    Callicarpa bodinieri (beautyberry)
    Cotoneaster (for foliage)
    Dahlia
    Echinops
    Elaeagnus (foliage)
    Eryngium
    Heather
    Hebe (flowers and foliage)
    Helichrysum (straw flower)
    Lavender
    Acer (Maple: foliage)
    Quercus (Oak: foliage)
    Skimmia
    Limonium (Statice)
    Viburnum tinus

    Here is a link to the Washington Park Arboretum web page of seasonal highlights.

    A great book on flowers by season is A Year Full of Flowers: Fresh Ideas to Bring Flowers into Your Life Every Day by Jim McCann and Julie McCann Mulligan.

    Season All Season
    Date 2007-03-03
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    Keywords: Washington Park Arboretum, Rhododendrons--Washington

    PAL Question:

    Would you be so kind as to tell me when rhododendrons are usually at their peak bloom?

    View Answer:

    The peak season for Rhododendron blooms would probably be May, but there are Rhododendrons which bloom earlier and later than this as well (March through June). For more detail about which species bloom at what time, you may find this link to Oregon State University's Landscape Plants web site of interest.

    From the Washington Park Arboretum's list of plants at their peak:

    March: Camellia, flowering cherry, corylopsis, daphne, forsythia, heather, hellebore, magnolia, rhododendron, witch hazel.

    April: Azalea, barberry, camellia, flowering cherry, halesia, maple, madrona, magnolia, rhododendron, serviceberry.

    May: Crab apple, dogwood, magnolia, mountain ash, rhododendron, red bud, serviceberry.

    June: Rock roses, brooms, Korean dogwood, rhododendron, stewartia, styrax

    Season Summer
    Date 2007-02-28
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    Keywords: Chionanthus, Flowering of plants

    PAL Question:

    Chionanthus virginicus--at what time can this tree be expected to bloom? And how does it do in the Pacific Northwest? Does this tree needs to reach a certain age or maturity before it blooms--similar to Cornus kousa or some magnolias? Or could it be a cultural problem that keeps it from blooming? Mine is in full sun, moist/fertile soil. It's been there 3 years and is probably 6 feet tall and over 5 years old (purchased balled and burlapped). Could it be getting too much nitrogen, as it is on the edge of the lawn?

    View Answer:

    According to local author Arthur Lee Jacobson's book, North American Landscape Trees (Ten Speed Press, 1996), Chionanthus virginicus blooms between May and July, depending on the year and the latitude. Male and female flowers are on separate trees, and male flowers are more showy. Sunset Western Garden Book also says that this tree flowers here in late spring to early summer. Here is what Oregon State University's web site of Landscape Plants says:

    • "Deciduous, large shrub or small tree, spreading, open, 12-20 ft (4-6 m) tall with an equal spread, larger in the wild. Leaves simple, opposite, sub-opposite, narrow-elliptic to oblong or obovate-oblong, 7.5-20 cm long, acute to acuminate, margin entire, glossy dark green above, underside paler and pubescent, at least on veins. Dioecious - male and female plants, but some have perfect flowers. White flowers showy, in fleecy, soft clusters in late spring. Fruit about 13 mm long, egg-shaped, dark blue in late summer.
    • Sun to partial shade. Adaptable but does best in moist, fertile, acid soils. Slow growing. Male trees reportedly have showier flowers."

    There are a number of reasons why your tree has not flowered. According to The Hillier Manual of Trees and Shrubs, flowers are not seen on young trees (no specifics as to age of maturity, unfortunately). Purdue University Extension indicates other reasons plants fail to flower.

    The full sun and moist soil sound like ideal conditions. It is quite possible that nitrogen-heavy fertilizer could contribute to the lack of flowers. You might consider applying compost to your lawn for nutrients instead of whatever you may have been using. Perhaps you could avoid using the fertilizer and give the tree at least another year to adjust and attempt to flower.

    Season Summer
    Date 2007-03-15
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    Keywords: Weed control, Equisetum, Lonicera, Geranium, Cistus

    PAL Question:

    What does "horse grass" look like? According to Ciscoe, it can't be gotten rid of and I want to see if this is what I have.

    View Answer:

    I wonder if you are referring to horsetail, or Equisetum, which is a very persistent weed.

    Wikipedia has a picture, and here is another from CalPhotos

    Here is an article on Field Horsetail and Related Species from Oregon State University Extension.

    Here is what Ciscoe Morris said about this plant in the Seattle P-I (April 29, 2006):

    "Hands down, horsetail (Equisetum arvense) is the worst weed you can get in your garden. If you've got it, just be glad you weren't gardening in prehistoric times. Back then, horsetail grew to 90 feet tall and you were in danger of being stepped on by a brontosaurus while weeding.

    The worst thing about horsetail is the speed with which it returns to make your life miserable after you weed it. No matter how great a weeding job you do, it will be back, practically to full size, within a week!

    Do what we did at Seattle University. Plant a mix of shrubs, ground covers and fast-growing perennials that are thick and tall enough to hide the horsetail. Shrubs that hide horsetail include Cistus (rockrose) Lonicera pileata (privet honeysuckle) Lonicera nitida (Box honeysuckle) and rosemary. My favorite perennial to hide horsetail is the prolific hardy Geranium oxonianum 'Claridge Druce.' It will seed all over your garden, but new seedlings are easy to remove in spring. These drought-tolerant plants look great in their own right and because they are so thick and tall, no one will see the hoards of horsetail growing within."

    Washington Toxics Coalition recommends controlling it by persistently hand-pulling or hoeing the above-ground growth as soon as it appears. This will weaken the plant over time. It does die back over winter, when you could cover the affected area with black plastic (for a duration of 2 years), but even this may not be entirely successful.

    An article by Irene Mills in the Fall 2008 issue of the Northwest Perennial Alliance's Perennial Post says that pulling, digging, and covering with black plastic are a waste of time. The author recommends keeping an eye out in April for emerging spore-bearing stalks, and cutting these off and disposing of them in the garbage. She suggests improving the soil texture (improve drainage, add organic matter, increase soil fertility, and in some cases increase soil pH). She recommends this guide called "Controlling Horsetail" from Swanson's Nursery, originally published in Gardens West by Carol Hall.

    Season All Season
    Date 2007-03-23
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    Keywords: Lawns--Planting, Weed control, Lawns

    PAL Question:

    I am looking for general information on lawn care, lawn renovation, lawn fertilizer and alternatives to pesticides.

    View Answer:

    Here is information from the web pages of Seattle Public Utilities. An excerpt:

    Fertilize Moderately:
    Use "Natural Organic" or "Slow-release" fertilizer. These fertilizers release nutrients to feed the lawn slowly, and less is wasted through leaching or runoff into our streams. Look for the words "natural organic" or "slow-release" on the bag.

    Fertilize in September and May:
    With slow-release or organic fertilizers, you can fertilize just twice a year, in mid to late May and again in early September. If you choose to fertilize only once, the fall application is most important because it helps the grass grow new roots and store nutrients for next year's growth.

    How much to apply:
    Washington State University (WSU) recommends that home lawns receive 3 to 4 pounds of nitrogen (in a balanced fertilizer) per 1000 square feet of lawn each year. Grasscycling can supply at least one-quarter of that. Split the rest between the May and September applications. Avoid fertilizing in the early spring because it makes lawns grow too fast (unless your lawn needs help recovering from disease or insect damage.) Wait until May.

    Mow better:
    Grasscycling returns valuable nutrients to the soil every time you mow! Mow high, mow often and leave the clippings to see results.

    Fertilize for a healthy colored lawn"
    Healthy lawns are a medium green color (top), depending on the variety of grass. The darkest green turf (bottom), which many people strive for, is not in fact the healthiest turf. Overfertilized lawns are more prone to disease, thatch buildup, and drought damage.

    Test for calcium deficiency:
    Soils west of the Cascades are often low in calcium. Apply lime in the spring or fall if a soil test shows a calcium deficiency or acid soil conditions (pH less than 5). Call WSU Cooperative Extension (206) 296-3900 for information on soil testing and their Home Lawns bulletin."

    If you would like to renovate your lawn, this is something you could do in the fall. Local garden writer Ann Lovejoy describes her method in The Handbook of Northwest Gardening (Sasquatch Books, 2003):

    • Mow the existing grass as short as possible.
    • Spread 1 inch of clean crushed quarter-ten gravel (not pea gravel) evenly over the entire surface.
    • Spread 1 inch of compost over the gravel.
    • Top-seed with a regionally appropriate blend if the lawn is thin and spotty.
    • Wait 6-7 weeks before mowing again.

    Should you decide to start afresh, here is information from the Washington State University Extension website which discusses grass seed for Western Washington gardens. Here is an excerpt:
    What Grass Seed Grows Well in Western Washington?
    "To establish a lawn in western Washington, choose a combination of turftype tall fescue grasses and turftype perennial rye grasses. A mix that adds up to about 90% of these two grass seed types will grow well in either sun or light shade in western Washington. Turftype perennial ryegrass takes full sun and stands up to traffic. Turftype tall fescues are adapted to shadier locations. In combination, the mix works for a lawn in average light conditions. Mixes containing fine-leaved fescues or chewings fescues will also establish well. Fine-leaved fescues offer bright green color, and will take some shade, but do not take heavy use.

    "Many commonly-grown grass types from other areas of the United States will not thrive in western Washington's cool, dry summer climate. AVOID mixes with high concentrations of Kentucky blue grasses. DO NOT PLANT Zoysia, bermuda, dichondra, centipede, carpetgrass, St. Augustine, or mondograss. Buffalograss isn't suitable for western Washington, though it may thrive in eastern Washington.

    Soil Conditions for Planting a New Lawn:
    "Establishing a new lawn successfully depends more on the preparation of the ground before planting than on whether the lawn choice is seed or sod. Lawn failures are often caused by poor soil conditions under the roots. Many times soil surface left for planting after new construction is infertile subsoils, with rocks, lumps, and building detritus left in it. The texture may vary from sands and gravels to heavy, poorly drained clay areas. The best soil texture for a lawn is a sandy loam, containing 60%-70% sand and 30%-40% combined silt and clay."

    If the soil isn't well-drained, do not try to amend a heavy clay by dumping sand into it. Adding sand doesn't work, nor does adding gypsum. Amend the soil with organic material, which will help in creating better structure. Use compost, manure, aged sawdust, ground bark, or other organic (previously living) materials. Spread 2 inches on top of the ground and work it in thoroughly 6 to 8 inches down. Getting it completely incorporated is important, because spots of organic material in clumps may decompose and cause a low spot in the finished lawn. Rake away clods and remove large rocks and litter.

    University of Minnesota Extension's "How Can I Maintain a Healthy Lawn on My Lakeshore" describes best practices for caring for a shoreline lawn and garden, which includes using compost as lawn fertilizer. An excerpt:

    • If possible avoid the use of chemical fertilizers. Native vegetation does not require the application of additional fertilizer. Use caution if applying fertilizers to lawns and adhere to the following guidelines:
      Have your soil tested to determine how much fertilizer is needed and minimize the use of chemical fertilizers; soil test sample bags are available through the county offices of the University of Minnesota Extension Service.<
    • Use compost or manure; this is preferable to chemical fertilizer. However, these also have the potential to damage water quality if used in excessive amounts.
    • If chemical fertilizers are used, select slow-release (water insoluble) forms; see recommendations for fertilizing on next page.
    • Water your lawn after fertilizing, but do not allow excess water to run off into surface waters.
    • Sweep up any fertilizer spilled on hard surfaces such as walks and driveways, instead of washing it off.
    • Use extra caution when applying fertilizer near surface waters; do not spread fertilizer within 75 feet of surface waters or wetlands; use a "drop" spreader and not a "cyclone" spreader to minimize the possibility of getting fertilizer directly into the water.
    • Never apply fertilizers to frozen ground.
    • Leave a natural vegetation filter strip of grass, trees, and/or shrubs next to the shoreline; another option would be to construct a berm along the shore.

    You may find this general information about compost, from the City of Seattle Public Utilities and the Saving Water Partnership, of interest.

    Here are additional links to lawn care methods. The first three are from the Northwest Coalition for Alternatives to Pesticides:

    Taking Care of Your Lawn without Using Pesticides.

    Dealing with Dandelions.

    Pesticide-Free Techniques for Dealing with a Mossy Lawn.

    From Washington Toxics Coalition:
    Choosing Fertilizers for the Lawn & Garden.

    From Beyond Pesticides:
    Read your "Weeds"--A simple Guide to Creating a Healthy Lawn.

    Season All Season
    Date 2007-04-20
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    Keywords: Hemerocallis

    PAL Question:

    Can you recommend an evergreen daylily for this area? There are none listed with Greatplantpicks.org, but surely there must be some that thrive in this area. I'm trying to purchase bare root to save on costs, and haven't had much luck.

    View Answer:

    There are several evergreen daylilies which should do just fine in our area. Here is some information from University of Vermont Extension (where winter is more of an issue):
    Excerpt:
    "Catalogs list daylilies as D (dormant), SE (semi-evergreen), or E (evergreen). Dormant daylilies stop growing and drop their leaves when the days are short, much like deciduous trees. Evergreen daylilies are not affected by short days and hold their foliage until it is literally frozen off during the winter. Semi-evergreens are somewhere between dormants and evergreens. Many evergreen daylilies are perfectly hardy in the North, but the foliage may be somewhat unattractive in early spring."

    You might get some ideas from this article published in the Seattle Times by Valerie Easton. B & D Lilies, a Port Townsend area nursery lists several evergreen cultivars, and some are available as bare root plants.

    Season All Season
    Date 2008-02-06
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    Keywords: Screens, Cedrus

    PAL Question:

    I need a large tree for privacy and would like it to be fast growing here in Seattle. I would not like it to be much more than 15 feet wide at maturity but the height doesn't matter, also evergreen. Would an Incense cedar grow fast?

    View Answer:

    In addition to Calocedrus decurrens (Incense Cedar), you might also consider Podocarpus or Cryptomeria.

    You may want to consult the locally created web pages of Great Plant Picks, and see which evergreen trees they recommend for our area. This is their list of conifers, and here is the information on Incense Cedar.

    Incidentally, Great Plant Picks says that Incense Cedar does make a good screening plant. They claim it will mature at 35-40 feet tall in garden conditions (as opposed to in the wild), and about 10 to 12 feet wide, so your original idea of planting this tree sounds like a good one.

    Season All Season
    Date 2007-03-21
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    Keywords: Botanical nomenclature

    PAL Question:

    What does it mean when a plant name is described as a synonym? And is a synonym "valid?"

    View Answer:

    It can get confusing when plant taxonomists decide to change the names of plants. According to the International Code of Nomenclature (Melbourne Code, 2011), a replacement name "is a new name based on a legitimate or illegitimate, previously published name, which is its replaced synonym. The replaced synonym, when legitimate, does not provide the final epithet, name, or stem of the replacement name." To me, that sounds like the synonym is the name which is no longer current. This link from Stephen Saupe of the biology department at St. John's University, Collegeville, MN is a little easier to understand. Here is an excerpt:

    "The correct name for a plant is the oldest, validly published name. Although this sounds simple, in practice it can be challenging to sort through all of the names that have been published for a species and determine which is the correct one.

    "Although it may seem that botanists change scientific names just to frustrate us, this is not the case. Names are changed because additional scientific study shows that the original name: (1) didn't follow the rules (i.e., wasn't the earliest, or is taxonomic or nomenclatural synonym) or (2) because our taxonomic ideas of the genus and species has changed since the original study (i.e., additional studies showed that two closely related species are actually one). Perhaps this is a good time to mention taxonomists who are 'splitters' (focus on the differences between taxa) and those who are 'lumpers' (focus on the similarities)."

    As you may have noticed, people often continue to refer to plants by invalidated names. And sometimes the rejected names are made valid again later. Unless you are publishing a scholarly article and need to be precise and up-to-date about the plant names, aim to use names that people will recognize and understand.

    Season All Season
    Date 2013-04-27
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    Keywords: Cicer arietinum, Crops and climate

    PAL Question:

    I'm interested in growing garbanzo beans. Do they work in the Seattle climate?

    View Answer:

    The following information from University of Wisconsin's Alternative Field Crops Manual indicates that garbanzo beans are grown as a crop in Eastern Washington.

    According to Steve Solomon's Growing Vegetables West of the Cascades (Sasquatch Books, 2000), Cicer arietinum should be sown here in early March to early April, the earlier the better, because the crop needs soil moisture. However, you should sow when the soil is warm enough for the seed to sprout. Plant an inch deep, 3 to 4 seeds per foot, in rows 3 feet apart. You can mix compost into the rows before planting, which should be sufficient nutrition for the plants. If you need to amend the soil further, you may add bone meal with the compost (5-10 lbs./per 100 row feet). Thin the seedlings once established to 8 inches apart. Keep the planting well weeded. Harvest in midsummer.

    Season All Season
    Date 2007-04-07
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    Keywords: Zinnia, Daisies, Verbena, Coreopsis, Artemisia, Salvia, Lavandula, Achillea, Echinacea, Herb gardens, Xeriscaping, Tagetes, Sedum, Container gardening

    PAL Question:

    Our neighborhood has a small planter area at its entrance. There is no water supply to this area, but a nearby resident is willing to water occasionally. The soil contains much clay. We would like to plant a few drought-tolerant annuals to add color and supplement the more permanent shrubs--such as boxwood--planted in the area. Can you recommend some plant choices? How could we amend the soil to best hold water during the upcoming dry months? Would a commercial product such as "Quench" be of any value, in addition to organic mulches?

    View Answer:

    I found the following article by Nikki Phipps on GardeningKnowHow.com about drought-tolerant container planting. Here is an excerpt:

    "...many plants not only thrive in containers but will tolerate hot, dry conditions as well. Some of these include annuals like marigolds, zinnias, salvia, verbenas, and a variety of daisies. Numerous perennials can be used in a xeriscape container garden such as Artemisia, sedum, lavender, coreopsis, Shasta daisy, liatris, yarrow, coneflower and more. There is even room for herbs and vegetables in the xeriscape container garden. Try growing oregano, sage, rosemary, and thyme. Vegetables actually do quite well in containers, especially the dwarf or bush varieties. There are also numerous ornamental grasses and succulents that perform nicely in containers as well."

    The Brooklyn Botanic Garden's book The Potted Garden (21st Century Gardening Series, 2001) provides a list of drought-tolerant plants for containers.

    I had not heard of Quench, but since it is cornstarch-based, it is certainly preferable to the hydrogel and polymer products which are more widely available. I found an article by garden writer Ann Lovejoy in the Seattle P-I (June 3, 2006) about Quench. Here is an excerpt:

    With pots and containers, mix dry Quench into the top 12 inches of potting soil in each pot and top off with plain compost. Few roots will penetrate deeper than a foot, so it isn't very useful down in the depths of really big pots unless you are combining shrubs and perennials.

    I would not recommend hydrogels or polymers as a soil amendment. Professor Linda Chalker-Scott of Washington State University has written about these products and their potential hazards. Here is a link to a PDF.

    You could consider applying a liquid fertilizer (diluted seaweed-fish emulsion would work) to your containers once every week or two during summer. Here is general information on container maintenance, from Ohio State University Extension. Excerpt:

    "Once planted, watering will be your most frequent maintenance chore, especially if you are growing plants in clay containers. On hot, sunny days small containers may need watering twice. Water completely so that water drains through the drainage hole and runs off. Water early in the day.

    "If you incorporated a slow release fertilizer into the potting mix, you may not need to fertilize the rest of the season; some of these fertilizers last up to nine months. You can also use a water-soluble fertilizer and apply it according to the label directions during the season.

    "Mulch can be applied over the container mix to conserve moisture and moderate summer temperatures. Apply about one inch deep.

    "Depending on the plants you are growing, you will need to deadhead and prune as needed through the season. Monitor frequently for pests such as spider mites. Pests usually build up rapidly in containers."

    Season All Season
    Date 2007-04-05
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    Keywords: Hedera, Transplanting

    PAL Question:

    Do you have any information on how to transplant Hedera colchica?

    View Answer:

    Before you transplant your ivy, be sure to verify that it is not on your county's noxious weed list. Hedera colchica, or Persian ivy, is not listed on King County's site, but it may still share some of the self-perpetuating and plant- and structure-damaging properties of English ivy (Hedera helix).

    I searched our books on ivies as well as our periodicals databases, and did not come across anything specifically about moving Hedera colchica. I would assume that what applies to the genus, as far as the procedure for transplanting, should apply to this species also. Below is general information I located.

    The American Ivy Society has general information on moving outdoor ivies. Search under "Resources: Q & A."(You may wish to contact them directly for information specific to Hedera colchica). Here is an excerpt:

    "You can dig up ivy fall or early spring and move it. If you are in a really cold climate you will best results transplanting in the spring.

    "Dig around the base of the ivy stem leaving as much root & soil as possible. Dig the new hole wider and deeper than the root ball. It is good to plant ivy deeper-- as much as 3-4" deeper if possible. That will secure the ivy in the ground and help to prevent drying while it acclimates to the new location. Water regularly making sure the ivy does not dry out but do not keep the soil too wet.

    "I would suggest mulching with almost any organic mulch like pine needles, leaves or chipped bark. This also helps to keep the soil moist and the temperature even.

    "You will need to give the ivy some TLC for the first few months but once it gets started it should be fine. It is always a good idea to keep newly planted ivy carefully water for the first year or so. After that you can practically ignore it (depending on your climate) and it will survive with the natural rains or normal garden irrigation."

    From The Helpful Gardener, an online garden forum:

    • First thoroughly water the plants and cut off a lot of the top growth to prevent dehydration (down to where there is growth evident - don't cut into old wood where there isn't anything growing from it).
    • Then dig the new holes for them - making them large and deep - and dig in some compost. Carefully dig up the ivies, taking all the roots and some soil around them, and put each in a bucket or piece of sacking.
    • Next, making sure the new hole is big enough, replant the ivies in their new homes, shaking the plant gently so that the soil settles around the roots.
    • Heel in gently, water generously, put some shredded bark or shingle on top to keep in the moisture, and keep well watered during dry spells.

    Season All Season
    Date 2007-04-04
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    Keywords: Moss gardening, Lawn alternatives, Ground cover plants

    PAL Question:

    What is the best way to encourage moss to take over and cover large surface areas in a relatively short amount of time? My goal is to replace my lawn with a moss garden.

    View Answer:

    Here are some links to information which may be useful to you:

    Primitive Plants: Bryophytes, Ferns, and Fern Allies

    Moss cultivation:

    Encouraging Mosses

    Mad About Moss: The Simple Art of Moss Gardening

    There are two books I would recommend, Moss Gardening by George Schenk (Timber Press, 1997), particularly the chapter on "Moss Carpets," and How to Get Your Lawn Off Grass by Carole Rubin (Harbour Publishing, 2002). Rubin gives directions for preparing your site, which involve digging out existing plants or--in your case--smothering the lawn with mulches of leaves (12 inches), bark (3 inches), or newspaper (10 sheets thick). Schenk offers several different methods for creating a moss garden. Briefly paraphrasing, these are:

    1. Work with nature, allowing self-sown spores of moss to take hold. (Prepare the site by weeding, raking, and perhaps rolling the surface smooth.)
    2. Encourage the moss in an existing lawn by weeding out grass. You can plant what the author calls "weed mosses" which will spread, such as Atrichum, Brachythecium, Calliergonella, Mnium, Plagiothecium, Polytrichum, and others.
    3. Instant carpet: you can moss about 75 square feet if you have access to woods from which large amounts of moss can be removed legally.
    4. Plant moss sods at spaced intervals (about one foot apart) and wait for them to grow into a solid carpet.Choose plants that match your soil and site conditions.
    5. Grow a moss carpet from crumbled fragments. This is rarely done, and only a few kinds of moss will grow this way, including Leucobryum, Racomitrium, and Dicranoweisia.

    Another approach is to change the soil pH. Sulphur should be beneficial to moss and detrimental to lawn grass. The reason for this lies in the fact that moss grows best with a soil pH of 5.0-6.0, while lawns grow best with soil pH between 6.0 and 7.0 (according to The Lawn Bible by David Mellor, 2003). Added sulphur lowers the soil pH, creating a more acidic environment.

    Season All Season
    Date 2007-04-04
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    Keywords: Wood chips, Phytophthora

    PAL Question:

    I have two 40' trees diseased with Phytophthora lateralis that I am having removed tomorrow. Can I chip the branches and spread them in my garden or will this spread the disease to other plants?

    View Answer:

    Although the following information from Washington State University Extension refers to a different species of Phytophthora, I imagine that the same precautions hold true.
    Excerpt:
    "P. ramorum can be spread to other hosts through air, water, rain, soil and plant debris. People can move it via plants, plant material, soil, plant products, wood, woodchips, dirty shoes, and water. P. ramorum does best in cool, wet climates (like ours)."

    A resource from Oregon State University confirms this for both commonly found species of Phytophthora fungus:

    Generally, one does not need to worry about plant diseases being spread by wood chips, because "they cannot compete well with wood-decay fungi. Uncomposted plant materials can, however, carry two important diseases of woody plants: Port-Orford-cedar root rot, caused by Phytophthora lateralis, and Sudden Oak Death (Phytophthora ramorum). Many diseased Port-Orford-cedar trees are disposed of by chipping, and mulch made from these chips can spread disease to healthy plants."

    Season All Season
    Date 2012-07-05
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    Keywords: Soil testing

    PAL Question:

    Can you tell me how alkaline soils are formed and if and how they are related to saline soils?

    View Answer:

    Saline soil may have a high pH, a characteristic shared with soils which are alkaline. You may find this information on soils and pH useful:

    Diagnosing Saline and Sodic Soil Problems

    Plant Materials for Saline-Alkaline Soils

    Soil pH: What it Means

    • Alkaline soil: A soil whose reaction is greater than pH 7.
    • Acid soil: A soil whose reaction is less than pH 7.
    • Saline soil has a pH less than 8.5.

    Saline soil, as defined in Soils: An Introduction, by Michael Singer and Donald Munns (Prentice Hall, 1999): "Saline soils ...contain large amounts of soluble salts, appreciably more soluble than calcium sulfate. Most commonly, these are salts of Na, Ca, and Mg, with chloride, sulfate, and bicarbonate...soils are considered saline if their electrical conductivity exceeds 4 deciSiemens meter-1. Many plants suffer at this level."

    To answer your question about how alkaline soils are formed, here is what Clemson University Extension says:
    "The pH value of a soil is influenced by the kinds of parent materials from which the soil was formed. Soils developed from basic rocks generally have higher pH values than those formed from acid rocks."

    Rainfall also affects soil pH. Water passing through the soil leaches basic nutrients such as calcium and magnesium from the soil. They are replaced by acidic elements such as aluminum and iron. For this reason, soils formed under high rainfall conditions are more acidic than those formed under arid (dry) conditions.

    Application of fertilizers containing ammonium or urea speeds up the rate at which acidity develops. The decomposition of organic matter also adds to soil acidity.

    Season All Season
    Date 2007-04-04
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    Keywords: Hoya bella, Propagation

    PAL Question:

    Do you have any information on how to propagate Hoya bella?

    View Answer:

    I consulted The American Horticultural Society's Plant Propagation (ed. Alan Toogood, DK Publishing, 1999) for information on propagating Hoya. This plant can be propagated by seed in spring or summer, and by cuttings, from spring to summer.

    If the seeds are sown fresh and kept moist at 70-81 degrees, they should germinate in a few days. It is more common to increase this plant by cuttings. Cut a length of stem just below a leaf node. The cutting should be 3 to 4 nodes long. Dip its base in rooting hormone (which will also help stop the ooze of sap). Root as you would a stem cutting--fill a pot with a medium of fine grit (top 1/4 of pot) layered on top of gritty cactus soil mix (bottom 3/4 of pot). Gently push the cuttings through the fine grit into the soil mix. Keep slightly damp, but not too humid. If it is not warm enough in your home, provide gentle bottom heat to 70 degrees. They should root in 2 to 6 weeks. New plants will take a year or two to flower.

    Season All Season
    Date 2007-04-13
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    Keywords: Shrubs--Wounds and injuries, Effect of storms, Arbutus unedo, Frost

    PAL Question:

    I live in Monroe (Zone 7). Two years ago I planted 3 Arbutus 'Compacta'. I have never pruned them. This year they took the cold winter pretty hard: over half of the leaves are golden/brown/black, with some already falling off. Will the leaves be replaced or do I need to cut the branches and stems to those leaves and hope for the best? The tree/shrubs are in well-drained soil, mulched, facing south/southwest. The leaves hurt the worst were on the upper and north facing side.

    View Answer:

    It sounds like you are seeing winter damage on your plant. You should probably wait and see if the plant returns to more robust health, and to see if new growth develops where those leaves have dropped before deciding whether to prune it at all. The local web site Great Plant Picks indicates that Arbutus unedo 'Compacta' can be cold-sensitive. Arbutus unedo 'Compacta' tolerates a wide variety of soil conditions. It grows best in part or full sun and is drought tolerant once established. There are few insect and disease problems, though it can occasionally get aphids and there may be fungal spotting on older leaves if grown in very poor soil. Foliage and flowers may be damaged in extremely cold winters. If you think that there is something else going on besides winter injury, I would recommend taking a sample to a Master Gardener Clinic for diagnosis.

    Below is information on winter injury from Washington State Extension and the Pacific Northwest Plant Disease Management Handbook.

    Season All Season
    Date 2007-04-13
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    Keywords: Prunus tomentosa, Failure to fruit, Fruit trees--Cross-pollination

    PAL Question:

    I have had a Nanking cherry bush that I planted 3 years ago. The first year, as I expected, it didn't produce flowers or fruit. The second year, it produced some flowers and about 4 small green cherries, which disappeared off from the bush in about a week. This year, it had a lot of flowers, but only produced 2 small green cherries, which also disappeared in about a week. I only have the one bush, and it seems very healthy otherwise. Is it due to being so young still? Do I need a second plant? Any advice would be greatly appreciated.

    View Answer:

    According to the following information, Nanking cherry (Prunus tomentosa) needs cross-pollination, so you do need two or more plants to have successful fruit production.

    Information from Alberta, Canada's Agriculture and Rural Development website (no longer available online) has some suggestions on cross-pollination:
    "Nanking cherries need cross pollination, for fruit production, therefore more than one plant is required, or an early flowering plum such as Brookgold, Bounty or Dandy. Mature plants reach heights of up to 2 m. Plant in rows 3 m apart with 2 m between the plants in the row. Prune annually to prevent shrubs from becoming too dense. Remove no more than one-third of the total number of branches at one time. This allows the plant to replace older wood with young, vigorous wood."

    There is a chapter on Nanking cherry in Lee Reich's Uncommon Fruits Worthy of Attention (Timber Press, 2004) in which he states clearly that cross-pollination is needed (some information on the web says that it is self-fruitful...which might be true to a small extent, but you will have a much better crop with cross-pollination). Some key points: Nanking cherry does well in sun and well-drained soil. Full sun is preferable, but it will still bear fruit in a shadier spot. It grows vigorously, and can live 50+ years. "Annual pruning, though not a necessity, brings out the best in any Nanking cherry in terms of yield and fruit quality. Prune in late winter with the aim of keeping a bush open so that all branches are bathed in sun and quickly dried by breezes. Accomplish these goals by shortening some branches, removing others entirely, and leaving still others untouched. This pruning will also stimulate a steady supply of young, fruitful branches each year."

    Season All Season
    Date 2013-08-01
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    Keywords: Ranunculus, Invasive plants

    PAL Question:

    Can you tell me the spread of Ranunculus ficaria 'Green Petal'?

    View Answer:

    The Royal Horticultural Society's A-Z Encyclopedia of Garden Plants (ed. Christopher Brickell; DK Publishing, 1996) indicates that Ranunculus ficaria (now known as Ficaria verna) spreads a foot or more, but the following information, from a local gardener (Paghat) who grows several cultivars of this plant, suggests that "more" may be quite a bit more. Excerpt: Due to their being potentially invasive, we placed them where it would not matter, but might even be rather nice, if they spread a great deal.

    The species is considered invasive, as these sites indicate:

    From the Plant Conservation Alliance's "Least Wanted" list

    From the USDA site.

    It is possible the cultivar is less invasive than the species, but I would certainly keep an eye on it.

    Season All Season
    Date 2007-04-13
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    Keywords: Helianthemum, Helleborus, Heuchera, Propagation, Invasive plants, Invasive plants, Euphorbia

    PAL Question:

    I am wondering if the following plants can be divided or propagated successfully: Heuchera, Donkey Tail Spurge (Euphorbia), Corsican Hellebore, and Helianthemum.

    View Answer:

    I consulted The American Horticultural Society Plant Propagation book, edited by Alan Toogood (DK Publishing, 1999), and it says the following:

    1. Heuchera: by division or by seed in spring. Since cultivars may not come true from seed, I would recommend dividing your plants. Once spring growth has begun, lift the plant from the ground and remove small sections from around the edge (look for good roots, and 2-3 shoots).
    2. Euphorbia myrsinites: (Just a note: based on the USDA information that this plant is invasive in Oregon and banned in Colorado, I would think twice before propagating it. This species does a fine job of propagating itself, apparently. In general, the genus Euphorbia can be propagated by division in early spring, or from spring to summer, by seeds in fall or spring, and by cuttings in summer or fall, but if you were to propagate by cuttings, you would need to protect your skin from the sap.
    3. Helleborus argutifolius can be propagated by division after flowering, or by seeds in summer. Test seed capsules for readiness by gently squeezing. If the seed capsule splits to reveal dark seeds, it is ready for harvest. Wear gloves! H. argutifolius (Corsican hellebore) often self-seeds. Check around the base of the plant in spring. When each seedling has at least one true leaf, gently lift and transplant to moist, fertile soil in light shade.
    4. Helianthemum can be started from greenwood cuttings rooted in summer and fall, and by seeds sown in spring in a frost-free location.

    If you would like further information on the relative ease or difficulty of each of these methods for each of these plants, I recommend coming to the Miller Library and looking at our books and other resources on propagation. Here is a link to a booklist.

    Season All Season
    Date 2007-04-11
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    Keywords: Dracaena, House plants

    PAL Question:

    I recently repotted my Dracaena fragrans 'Massangeana.' Some of the leaves have turned brown. Can you tell me what might be causing this?

    View Answer:

    We cannot diagnose plant problems via email. However, we may be able to give you some ideas of what might be happening. The browning leaves could be the result of too much or too little water. The soil should be kept lightly moist, but avoid overwatering. Avoid giving fluoridated water, as this link from University of Vermont suggests this plant is sensitive to fluoride. It is also sensitive to temperature changes (up or down) and should not be near heating or air-conditioning vents. Repotting may have caused some stress to the roots. According to The Complete Houseplant Survival Manual by Barbara Pleasant (Storey Publishing, 2005), brown spots on leaves can be the result of sun scorch. This plant prefers moderate to bright indirect light.

    Here is a link to discussions from a gardening forum sponsored by the University of British Columbia. Here is another from the same site.

    Here are two links to information about diagnosing problems with houseplants. The first is from Penn State Extension and the second from University of Illinois Extension.

    Season All Season
    Date 2007-03-30
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    Keywords: Quirky, Daemonorops draco, Medicinal plants

    PAL Question:

    Someone told me about an herbal remedy called Dragon's Blood which is made of the resin of Daemonorops draco. It's supposed to be good for relief from pain and headaches. Can you tell me more about the plant, including its medicinal uses?

    View Answer:

    The plant in question, Daemonorops draco, is a type of palm (Family: Arecaceae). Here is the USDA Germplasm Resources Information Network page about this plant.

    The common name Dragon's Blood can refer to a number of different plant resins (such as those derived from Dracaena cinnabari, Dracaena draco, and Croton). The product you mention says it is derived from the palm Daemonorops draco. The resin of this plant has a history of use in folk medicine. The webpage of Cropwatch.org has additional information about the uses the several plants that are called Dragon's Blood, as well as their conservation status. Some of the plants are on the IUCN Red List of Threatened Species (Dracaena cinnabari is listed as vulnerable, as of 2009). This may be of interest to you because often the products you find for sale are not well-regulated, and there may be no way of verifying that the list of plant ingredients is either valid or complete.
    Here is an excerpt:
    "Few commodity dealers properly distinguish the various botanical origins of Dragon's Blood items, and over-exploitation is starting to threaten some sources."

    As for medicinal and other uses of substances called Dragon's Blood, here is more information from Cropwatch.org:
    "The term 'Dragons Blood' refers to a product obtained from the resin layer consisting of diterpene acids found on the surface of fruits of the climbing palms of the Daemonorops genus found in SE Asia, and often sold out of Sumatra, Malaya & Borneo. These reddish resinous products (usually encountered as granules, powder, lumps ('cakes'), or sticks ('reed') used in folk medicine as an astringent and for wound healing etc., and in other applications for colouring essential oils red to dark brown, in varnishes, staining marble, for jewelry and enameling work, and for photo-engraving. Mabberley (1998) suggests Dragons Blood was produced originally from Dracaena cinnabari, later from D. draco and more recently from Daemonorops spp.; Zheng et al. (2004) confirm this view and suggest substitutes for Dracaena spp. include Pterocarpus spp., Daemonorops draco and Croton spp."

    There is also an article by Jane Pearson published by the Royal Botanic Gardens at Kew (2002) on the uses of Dragon's Blood.
    Excerpts:
    "The term 'Dragons Blood' is interchangeably used to refer to plants from three quite different families: Dracaena cinnabari (Socotra) and Dracaena draco (Canary Islands) in the Dracaenaceae family; the palm genus Daemonorops (Malaysia), and the genus Croton (South America) in the Euphorbiaceae family. [...] Although Daemonorops resin is similar in appearance, its origin and preparation are different to Dracaena resin. The fruits are covered in small imbricate scales through which the resin exudes, forming a brittle, red resinous layer on the outside of the fruits. Collection occurs just before the fruit is fully ripe. [...] Although used in the same way as Dracaena, the powdered form of Daemonorops was used extensively, especially in America, as an acid resist by photo-engravers up until the 1930s. It also appears to be used in both traditional Chinese medicine and Chinese herbal folk medicine. Daemonorops is traditionally used to stimulate the circulation, promote tissue regeneration by aiding the healing of fractures, sprains and ulcers and to control bleeding and pain." [My note: Daemonorops draco is referred to as Xue Jie in Chinese medicine.]

    Please note that we are not medical professionals, so if you are considering using a substance which claims to contain Daemonorops draco, you should consult your healthcare provider. However, I can tell you that there are ongoing concerns about contamination of patented herbal remedies. University of Minnesota has information on traditional Chinese herbal medicine and related safety concerns.

    Season All Season
    Date 2010-04-29
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    Keywords: Pruning trees, Camellia

    PAL Question:

    I bought 2 small camellias a year ago. Their height and width at maturity will be about 10' x 8'. One has 3 trunks. Now they are 4' tall and the stems are so close, they are rubbing together and the branches cross-mingled. The trunks have hardened and are about 1/2" to 3/4" in diameter. Should I prune crossing branches and stems? Should I limit them to one or two trunks? If so, when and how should I prune? My goal is to have them limbed up or narrower at the bottom with a low tree canopy beginning at about 4'. They just finished blooming. The variety is Kremer's.

    View Answer:

    Pruning the camellias when they are done flowering, but before they form new buds, should be fine. You are right to observe that crossing branches and branches which are very close will pose a problem as the camellias grow. In Cass Turnbull's Guide to Pruning (Sasquatch Books, 2006), the author recommends selective pruning to thin out a camellia. Start by removing any dead wood, and then look for crossing and rubbing branches, taking out some (but not necessarily all--you don't want to strip the plant) of the most obvious problem branches. Since you have young plants, you should not have too much thinning to do. Turnbull's book also gives instructions for arborizing your camellia by removing the lower limbs. She recommends that you observe the branching structure before proceeding, and visualize what the plant will look like if you remove some of the branches.

    You may find this pruning guide helpful. See second page, section III on "Tree-likes."

    The American Horticultural Society Pruning and Training book edited by Christopher Brickell (DK Publishing, 1996) suggests pruning a young camellia by shortening overlong lateral branches to an upward growing sideshoot. Selecting a central leader (main trunk) is also recommended.

    Season All Season
    Date 2007-04-18
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    Keywords: Corylus

    PAL Question:

    My Corylus contorta has greenish yellow lichen on the branches. Should I be concerned and if so what should I do?

    View Answer:

    The lichen will not harm your Corylus contorta. Lichen is actually a sign that the air is relatively unpolluted.

    You may find this page of discussion from University of British Columbia Botanical Gardens of interest.

    Here is an excerpt from a 2007 entry formerly available on the site of Treelink, now part of the Alliance for Community Trees.

    No need for a preemptive strike against the lowly lichen. Lichens are composite, symbiotic organisms made up from members of as many as three kingdoms. The dominant partner is a fungus. Fungi are incapable of making their own food. They usually provide for themselves as parasites or decomposers. "Lichens are fungi that have discovered agriculture"-- lichenologist Trevor Goward.

    The lichen fungi (kingdom Fungi) cultivate partners that manufacture food by photosynthesis. Sometimes the partners are algae (kingdom Protista), other times cyanobacteria (kingdom Monera), formerly called blue-green algae. Some enterprising fungi exploit both at once. Most lichens grow very, very slowly, often less than a millimeter per year, and some lichens are thought to be among the oldest living things on Earth.

    Lichens are important in many ways in the habitat. Some make the nitrogen in the air usable to plants, They are homes for spiders, mites, lice, and other insects. All are important in the nutrient cycle in the places where they grow. Many lichens are very sensitive to pollution in the air. When there are too many harmful things in the air, lichens die. If you live where there are many lichens it probably means the air is clean. But, if there are only a few lichens in your neighborhood, the air you are breathing is probably clogged with automobile fumes or industrial wastes. Some trees and shrubs can develop a layer of fungi, algae, lichens or moss on their bark. These are non-parasitic organisms and do not injure the plants on which they grow.

    Season All Season
    Date 2007-04-18
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    Keywords: Native plant gardening, Nandina domestica, Cistus

    PAL Question:

    My landscaper has planted several Cistus marked Cistus x purpurea. He said it was a solid colored [pink/lavender] flower without spots at the base of petals. I have spent hours searching for a photo, all photos that refer to purpurea are spotted. They also are referred to as orchid rock rose. Once there was a picture of a unspotted shrub, referred to as Cistus and next to it was a spotted one that had the purpurea label. Can you shed some light?

    Also planted is Nandina domestica "Royal Princess." There is hardly any information available on my search for this. It appears to be pretty, but I did read that outside of Seattle, some nurseries on the west coast stopped selling it. Should I anticipate a problem with this plant ? I also read that in some eastern states Nandina domestica is invasive.

    View Answer:

    Here is what I found on the web page of the Royal Horticultural Society. The correct name is Cistus x purpureus.

    The Cistus website (a British site) has a photo gallery which shows there are both spotted and unspotted varieties of this plant, and there is even one which is white with spots, despite the purpureus in the name. Here is one without spots.

    Here is information from Forest Farm Nursery about Nandina domestica 'Royal Princess.'

    Here is an excerpt from San Marcos Growers site:

    Nandina domestica 'Royal Princess' (Heavenly Bamboo) - This is an upright growing shrub to 6 to 8 feet tall has very lacy foliage. Pinkish white flowers bloom in clusters at the ends of branches in the late spring and summer followed by a heavy set of red berries ( notably heavier than most Nandina cultivars). The foliage turns to burgundy in spring and later a orange-red in fall. Branching stands stiffly upright unlike typical Nandina domestica and the foliage has a much finer texture. Plant in sun or shade. Tolerates fairly dry conditions but looks better when given water occasionally. It is hardy to about 10 degrees F.

    Nandina is widely grown in our area, and so far has not exhibited the invasive properties it has in the Southern U.S. Several cultivars are listed on the Great Plant Picks website, which is created by local gardening experts, so I am assuming there should not be a problem with growing it here. If you are still concerned about it, the main way it becomes invasive is from the berries setting seed and spreading. You could plant native ornamentals in its place, if you wish. Here are links to information about native plant landscaping:

    Washington Native Plant Society
    PlantNative.org
    King County's Native Plant Guide

    Season All Season
    Date 2007-03-28
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    Keywords: Gardening to attract birds, Nandina domestica, Poisonous plants

    PAL Question:

    A rumor has been circulating among birders in our area (Puget Sound) regarding the toxicity of nandina berries to birds, specifically cedar waxwings. I use a fair amount of nandina in my landscape designs, so this is obviously a concern.

    How toxic are nandina berries for wildlife? How often do birds or other critters eat enough of the fruit to be damaging?

    View Answer:

    I think that people are probably referring to this study:
    Excerpt:
    "Nandina domestica berries contain cyanide and other alkaloids. For most cultivars of N. domestica, cyanogenesis is the most important intoxication factor. Cyanide glycosides are substances present in many plants that can produce highly toxic hydrogen cyanide (HCN). At least 2000 plant species are known to contain cyanide glycosides with the potential to produce HCN poisoning. Generally, most parts of the plants contain cyanogenic glycocides, the young rapidly growing portion of the plant and the seeds containing the highest concentration. At least 55 cyanogenic glycosides are known to occur in plants, many being synthesized from aminoacids as part of normal plant metabolism. Frost and drought conditions may increase cyanogenesis in some plant species. Cool moist growing conditions enhance the conversion of nitrate to aminoacids and cyanogenic glycosides instead of plant protein. Presumably, similar weather conditions during late winter and early spring in the study area might have favored increased cyanogenesis in N. domestica."

    Note that this is the first time a mass death of waxwings has been observed, studied, and related to Nandina. Also note that Nandina is invasive in southern states (which means there is probably a lot of it in Georgia, where the deaths were noticed). If there are diverse food sources for the birds in the landscapes you design, perhaps consumption of a few Nandina berries is less of an issue. Another thing to note is that there are a great many other plants whose fruit contains cyanogenic glycosides, and we are unlikely to be able to avoid planting every single genus with this characteristic.

    You could aim to plant several plants in each landscape you create which are the preferred diet of local birds. Here is information about the cedar waxwing's feeding habits.
    Excerpt:
    "Cedar Waxwings feed mainly on fruits year-round. In summer, they feed on fruits such as serviceberry, strawberry, mulberry, dogwood, and raspberries. The birds name derives from their appetite for cedar berries in winter; they also eat mistletoe, madrone, juniper, mountain ash, honeysuckle, crabapple, hawthorn, and Russian olive fruits. In summer Cedar Waxwings supplement their fruit diet with protein-rich insects including mayflies, dragonflies, and stoneflies, often caught on the wing. They also pick items such as scale insects, spruce budworm, and leaf beetles directly from vegetation."

    Season All Season
    Date 2013-08-27
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    Keywords: Magnolia, Container gardening

    PAL Question:

    I recently purchased a magnolia that had no tags on it. I have an extremely large pot that I would like to plant the magnolia in. My books at home lead me to believe that I should plant it in Azalea and Camellia potting mix. A local nursery has advised me that this would be fine, although another has said no. They also disagreed with my plan of putting rocks, bitumen, and old leaves in the bottom of the pot to help with drainage. They believe a quality potting mix and nothing else is the way to go. What are your suggestions?

    View Answer:

    Here is what the book, Magnolias: A Gardener's Guide, by Jim Gardiner (Timber Press, 2000) says about growing Magnolias in containers:

    ...considerable experience is needed to retain magnolias in a container for any length of time. The roots are particularly sensitive to being hot and dry during the summer months and frosted during the winter months... Evergreen magnolias and clones of Magnolia grandiflora, in particular M. grandiflora 'Gallissonniere,' can be grown in very large containers for indoor use in atria.

    I think if you take the matter of extreme heat and cold into consideration, you should be able to grow your magnolia in a container. I would be curious to know which species you have, because some get very large, and for these a container might not be a good choice. Magnolias prefer good, free-draining acidic soil that does not dry out, according to Rosemary Bennett's book, Magnolias (Firefly Books, 2002). Since Azaleas also prefer acidic soil, the idea of using Azalea and Camellia potting mix makes sense.

    You may find the following information on growing trees in containers helpful:

    Virginia Cooperative Extension: Trees for Landscape Containers and Planters

    University of Tennessee Extension: Trees to Plant in Containers or Wells

    UBC Botanical Garden Forum: A discussion on requirements for magnolias in containers

    UBC Botanical Garden Forum: A discussion on potting guidelines for a particular magnolia This discussion suggests that the container should be filled with soil-based compost which provides some nutrients to the plant.

    As for container drainage, here is what Prof. Linda Chalker-Scott of Washington State University says. In short, she says that putting coarse material in the base of a pot for better drainage is a myth.

    Season All Season
    Date 2007-03-28
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    Keywords: Juglans, Compost, Allelopathy

    PAL Question:

    Will black walnut leaves cause compost to be allelopathic? Should they be kept out of compost? Or is this folklore? The specific compost is made with chicken manure (fresh), grass clippings and walnut leaves. Are there plants that tolerate the toxin in black walnut?

    View Answer:

    It seems that the main source of toxicity is the roots of the walnut tree, rather than the leaves or shells. However, there are still those who believe that there is enough juglone in the leaves that they should be fully composted before use in the garden. Below are excerpts from information published online in various university extension websites, by various authors, and now unavailable:

    "This toxic affect on surrounding plants appears to be related to root contact, as walnut hulls and leaves used as mulch have not shown toxic effects on plant growth. [Warning- Frank Robinson disagrees.] Because Walnut roots do not occupy the surface layers in most soil, many shallow rooted plants growing under walnut trees don't come in contact with the roots and are not affected by them." [Michigan State University]

    "You've probably always heard that you should never add black walnut sawdust [or wood chips] to the compost pile because the juglone will kill everything that grows in the compost. Abraham says that's not necessarily true; that juglone is not found in walnut saw dust or wood chips. Nor do dead walnut trees exude juglone. Juglone is harmless to humans so you can go right ahead and safely eat fruit and vegetables grown near walnuts."[Katy Abraham]

    "Robinson doesn't agree on the use of walnut residue in composting. He has this to say about black walnut saw dust, husks and leaves affecting plants. 'Tomatoes growing in clean soil in pots were severely stunted when leaves and nuts fell into the pots while we were on vacation. I know what juglone can do. I have seen a 15-year-old rhododendron killed a few weeks after its owner mulched it with black-walnut husks, and roses injured by an application of compost containing black-walnut sawdust.'" [Robinson]

    "The juglone toxin occurs in the leaves, bark, and wood of the walnut but these contain lower concentrations than the roots. Juglone is poorly soluble in water and does not move very far in the soil. Walnut leaves can be composted because the toxin breaks down when exposed to air, water and bacteria. The toxic effect can be degraded in two to four weeks. In soil, breakdown may take up to two months. Black walnut leaves may be composted separately, and the finished compost tested for toxicity by planting tomato seedlings in it. Sawdust mulch, fresh sawdust or chips from street trees prunings are not suggested for plants sensitive to juglone, such as blueberry. However, composting of bark for a minimum of six months provides a safe mulch even for plants sensitive to juglone." [Ohio State University]

    "To be on the safe side, composted material containing juglone should be allowed to breakdown over a period of time before use. This composted material can be used with plants that are not susceptible to juglone damage. If it is important to use it for general composting purposes, testing it first with a few tomato plants for a few weeks should reveal its level of toxicity." [Abraham]

    This may also be of interest: The Walnut Tree: Allelopathic Effects and Tolerant Plants from the Virginia Cooperative Extension.

    Frank Robinson's article "Under the Black Walnut Tree," Horticulture magazine, October 1986, pp. 30-33 concludes that many plants are indeed able to tolerate juglone's toxicity. Some of the juglone-tolerant plants listed in the article and in other sources are included on Viette's Beautiful Gardens website.

    Season All Season
    Date 2008-03-27
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    Keywords: Ficus carica, Tree roots

    PAL Question:

    I have a fig tree cut down to just above the ground and want to know how to stop it from growing, i.e. putting up suckers. I plan to pave over that area and am afraid, because of its vigorous growth, that it will find a way up and out.

    View Answer:

    I recommend renting a stump grinder, or hiring a tree service to grind the stump and the larger roots. You can water the area well to soften the soil, and try digging up the remaining roots. You could try applying full-strength vinegar to kill any shoots, or you can wait and continue to cut them off as soon as they emerge. Over time, this should weaken any part of the tree that remains in the ground, and it will eventually die. You could also cover the area with black plastic once the stump and major roots have been removed. This should suppress any growth coming up from what is left of the roots. There are also chemical treatments which should only be used with extreme caution, and exactly according to directions on the product.

    If you look at page 4 of this document on controlling invasive species from the Hawaiian Ecosystems at Risk project, you will see the different approaches used to remove fig trees and their roots from a natural area (in Central California), including physical and chemical methods.

    Season All Season
    Date 2007-10-16
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    Keywords: Gaura

    PAL Question:

    I have planted at least two Gaura plants (I don't recall which varieties) in the past couple of years, but they only lasted one season. One was planted in a sunny location with excellent drainage. What could I be doing wrong?

    View Answer:

    I have had bad luck keeping Gaura going for more than a year also. Mine were planted in the sunniest, driest part of the garden, but they failed to thrive. Gaura can succumb to root or crown rot, drought, snails, slugs, or even winter damage (it's a good idea to mulch around it for protection against cold--keep mulch away from crown). Did you notice how they developed after you planted them? If there is any plant matter left, you could bring it to a Master Gardener Clinic for diagnosis.

    If you want to try this plant again, you could try obtaining it from another source (just to rule out preexisting disease as a cause), and continue to provide good drainage, full sun, and space around it for air circulation. According to Perennials: The Gardener's Reference by Carter, Becker, and Lilly (Timber Press, 2007), Gaura is "short-lived in heavy soil in the maritime Northwest. [...] We often use it as an annual; it is worth replanting on a regular basis."

    Season All Season
    Date 2007-05-02
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    Keywords: Soil amendments

    PAL Question:

    I have typical Seattle clay soil and I want to amend it before planting. I'm re-grading a large (~2000 sq. foot) area and have already added copious amounts of mulch, compost, overturned sod, etc. I'm planning on planting a cover crop of clover this summer, but before doing so thought it'd be a good idea to till in some sand. I was thinking about a level inch over the whole yard before tilling. Is there a particular chemical composition to use or avoid? How about grain size?

    View Answer:

    You may find this information from Colorado State University Extension on soil amendments useful. Excerpt: Don't add sand to clay soil--this creates a soil structure similar to concrete.

    Professor Linda Chalker-Scott of Washington State University also debunks the idea of adding sand to improve clay soil.

    For good advice on amending the soil, see these links:

    Building Fertile Soil and Cover Crops for the Garden. from the University of California, Santa Cruz Agroecology Program.

    Growing Healthy Soil from Seattle Public Utilities.

    It sounds to me as if you have already taken great steps toward improving your soil, and adding sand not only will not be necessary, but would not be a good idea.

    Season All Season
    Date 2007-05-02
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    Keywords: Starlings, Bird pests

    PAL Question:

    Starlings eat our figs before we can partake. Is netting the only sure solution or are there other methods?

    View Answer:

    Washington State Department of Fish and Wildlife's Living with Wildlife page on starlings mentions netting as well as bird-scare tape and other devices. Other sources suggest picking just-ripe figs early in the morning, and not leaving ripe figs on the tree--the birds know perhaps better than we do when the fruit it ripe.

    The netting is probably your best bet for the fig tree, although it is a bit cumbersome and unsightly. I imagine the figs are worth it, despite the aesthetic sacrifice.

    Season All Season
    Date 2007-05-04
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    Keywords: salt-tolerant plants, Shrubs, Seaside gardening, Perennials

    PAL Question:

    I need plant suggestions for growing in cold, salty winds only 15 to 20 feet from the high water mark of the Georgia Straits. In winter, the salt water from the ocean occasionally douses the area where I will be gardening. I'm particularly interested in perennials and small shrubs.

    View Answer:

    I found a list from Island County, WA with revisions added for Bay Area gardeners.
    Excerpts:
    "Some of the better salt-tolerant shrubs and small trees to consider include Salal (Gautheria shallon), Ocean Spray (Holodiscus discolor), Snowberry (Symphoricarpos albus), Elderberry (Sambucus species), Tall Oregon grape (Mahonia aquifolium), Serviceberry (Amelanchier alnifolia), Nootka Rose (Rosa nutkana), and the Wax Myrtle (Myrica [now called Morella] californica).

    There are a variety of native plants that are commonly found near the shoreline, and which typically do well in the Puget Sound area. These include the sword fern (Polystichum munitum), Bracken fern (Pteridium aquilimum), Fireweed (Epilobium angustifolium), Coastal lupine (Lupinus littoralis), Honeysuckle (Lonicera species), and Coastal strawberry (Fragaria chiloensis)."

    Washington Native Plant Society also has a list of plants for a saltwater setting.

    I recently answered a question about salt-tolerant grasses which may be helpful to you as well.

    The book cited in the answer above, Frances Tenenbaum's Gardening at the Shore, also lists shrubs and perennials. Below are those which might work in zone 8 or lower, and which are smaller than 20 feet.
    Shrubs:

    • Acca (also called Feijoa) sellowiana (8-12 feet)
    • Amelanchier (small tree/large shrub)
    • Arbutus (there are some smaller species than the familiar Pacific madrone)
    • Arctostaphylos patula (6 feet)
    • Arctostaphylos uva-ursi (ground cover)
    • Atriplex canescens (3-5 feet)
    • Baccharis halimifolia (6-10 feet)
    • Calluna vulgaris (from 6 inches to 2 feet)
    • Caryopteris x clandonensis (2-3 feet)
    • Ceanothus (many varieties of different sizes, from ground cover to 20 feet)
    • Chamaecyparis lawsoniana (look for a dwarf variety of this tree)
    • Clethra alnifolia (8 feet)
    • Gaultheria shallon (ground cover)
    • Hydrangea macrophylla (6-8 feet)
    • Juniperus virginiana (look for creeping juniper cultivars like 'Bar Harbor' and 'Blue Rug' which are salt-tolerant)
    • Picea glauca (look for dwarf cultivars like 'Arneson's Blue')
    • Rhus typhina
    • Rosa rugosa
    • Rosmarinus officinalis
    • Syringa vulgaris
    • Vaccinium corymbosum (highbush blueberry)
    • Viburnum (numerous species of different sizes)

    Perennials:

    • Achillea
    • Armeria maritima
    • Artemisia 'Powis Castle'
    • Artemisia schmidtiana
    • Asclepias tuberosa
    • Baptisia australis
    • Echinacea purpurea
    • Hemerocallis 'Stella d'Oro'
    • Nepeta x faassenii and Nepeta 'Six Hills Giant'
    • Perovskia atriplicifolia
    • Platycodon grandiflorus
    • Sedum 'Autumn Joy'

    Season All Season
    Date 2010-05-28
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    Keywords: Gaultheria

    PAL Question:

    I was wondering if you could figure out if there is a difference between Gaultheria mucronata and Pernettya mucronata. Are they the same plant that had a name change? Are they different? I had thought that P. mucronata had both male and female plants--could you confirm that?

    View Answer:

    Here is the Pernettya mucronata listing, and here is the Gaultheria mucronata listing, both from the U.S. Department of Agriculture's Taxonomy database, showing that the two names are synonyms.

    The University of British Columbia Botanical Garden online forum offers the following information:

    "Often known as pernettya, and less commonly as prickly heath, for many years this plant was placed in the genus Pernettya. This lasted until it was recognized that all members of the genus Pernettya were genetically indistinguishable from Gaultheria. As I mentioned in a previous entry, modern taxonomy suggests that nomenclature should reflect evolutionary relationships, so the names of all Pernettya species were changed in accordance with the evidence, and transferred to Gaultheria."

    Just to make things still more complicated, there is also x Gaulnettya.

    There are both male and female plants. See Plants for A Future's page about this plant.

    Additional information from a local gardener's web site.

    Season All Season
    Date 2007-04-20
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    Keywords: Thuja, Thuja plicata

    PAL Question:

    I have a golden cedar about 6 feet high. This winter many sparrows sat on the top portion while waiting their turn at the feeder. I don't know if they ate the leaves or if their little feet knocked them off, but many of the branches are stripped and brown. Will they come back? Should I cut them out and hope that new branches will fill in the spaces? It is approximately half of the front top of the tree. Or is it time to take it out? I would prefer not to, unless it can't be saved.

    View Answer:

    I am assuming that your golden cedar is a form of Thuja occidentalis or Thuja plicata. It is possible the sparrows caused the damage, but there could be other factors involved. It is difficult to tell without seeing the plant. Below are general comments on the liabilities of Thuja occidentalis as a landscape plant, previously available from the Ohio State University Extension website.

    • Winter evergreen foliage color is often an unattractive yellow-brown
    • very prone to bagworms and their feeding damage
    • very prone to branch separation under snow and ice loads
    • widens at its base with age, or separates into several leaning but divergent canopies with age (this applies to both upright and rounded cultivars)
    • does not recover from severe pruning (where the bare stems are exposed, although side branches may slowly envelope the dead stems)
    • interior foliage noticeably sheds in Autumn

    The defoliation you describe might also be the work of bagworms. If the tips of the branches are dying back, that could be a result of winter injury, drought stress, or a fungal disease. Since I cannot diagnose the problem remotely, I think it would be best if you brought a sample of the affected plant to a Master Gardener Clinic. If you are in King County, this link to their website will lead you to the current clinic schedule.

    Season All Season
    Date 2007-04-26
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    Keywords: Brunnera, Stachys, Liriope, Epimedium, Lamium, Rock garden plants, Shade gardening, Ground cover plants, Geranium

    PAL Question:

    I'm looking to plant in a narrow strip on our retaining walls some "spiller" plants which will overhang the walls (which face north).

    I'd prefer evergreen plants which would fill in fairly quickly, but I could also mix in slower-growing and deciduous plants. There's great drainage since I have gravel reservoirs behind each wall, and the part of the plant above the wall will get part to full sun, though I could overplant them if necessary for a plant that couldn't handle full sun.

    I would like plants with interesting foliage and form to soften the look of the walls, and so would prefer a furry look to a spiny one. Flowers and fragrance are less important though always nice, and I'm hoping to have at least 2 or 3 different plant types with different colored foliage (shades of green are fine).

    View Answer:

    Some of the plants that occur to me, based on the description of your site, are Brunnera macrophylla, Epimedium, Geranium phaeum, Stachys byzantina, Lamium maculatum, and Liriope. Of these, the Geranium and Lamium will trail somewhat, while the others are essentially upright.

    Graham Rice's article on the Royal Horticultural Society site features a selection of recommended trailing (or spilling) plants. Here is another good list of trailing plants for walls.

    You could also try entering your site requirements into the plant-finding and plant selection web pages below:

    Great Plant Picks (a local site)

    King County's native plant guide

    Missouri Botanic Garden Plant Finder

    Royal Horticultural Society Plant Selector

    The Miller Library has many books on gardening in the shade, so you may wish to come in and do some research to help you in your plant selection. Here is a booklist that may be of interest.

    Season All Season
    Date 2007-05-21
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    Keywords: Picea

    PAL Question:

    I am interested in planting a dwarf Colorado blue spruce in my yard (I live in Kirkland), but my landscaper said that blue spruce does not do well here. Is she correct? It is true that there aren't any on the Great Plant Picks list.

    View Answer:

    According to local gardener and author Arthur Lee Jacobson, Picea pungens f. glauca (Colorado blue spruce) is quite common in gardens here, but in his opinion it does not have many assets beyond its striking color and hardiness (North American Landscape Trees, Ten Speed Press, 1996). I wonder if your landscaper has observed that it is susceptible to spruce spider mites, aphids, and other pests and diseases. I see that it is susceptible to Phytophthora, which is often a problem in our area. The book Trees & Shrubs for Pacific Northwest Gardens by John and Carol Grant (Timber Press, 1990) concurs that Colorado spruce is not the best choice for our region because of pests and diseases. Newly planted trees will also need regular watering for their first year, and if they do not receive it, they are likely to suffer dieback or death. Here are links to additional information from the Washington State University and the Urban Forests Ecosystems Institute SelecTree site.

    Excerpt:
    Pest & Disease: Susceptible to Aphids, Scales and Spider Mites, Oak Root Rot, Phytophthora, Root Rot, Rust and Sooty Mold.

    If you love the look of this tree, you could try growing it despite the drawbacks, or you could look for other blue foliage conifers which may be easier to grow here. Great Plant Picks mentions Abies pinsapo 'Glauca,' though this is not a dwarf tree.

    You might want to search the Oregon State University Landscape Plants web pages for additional information on any other trees you are considering for your garden.

    Season All Season
    Date 2007-05-16
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    Keywords: Rosa

    PAL Question:

    I would like more information on Rosa chinensis 'Mutabilis', particularly regarding how it performs in a Seattle garden. I am most concerned about black spot and any other diseases.

    View Answer:

    I am currently growing this rose for the first time, and it is blooming profusely. I have needed to keep on top of the aphids (hand-squishing), and there are a few yellowed leaves which drop (and which I have been picking up and destroying as soon as I see them). Here is what the book Roses for the Pacific Northwest by Christine Allen (Steller Press, 1999) has to say about this rose:

    Few old roses flower so continuously--cold weather merely turns the buds a paler hue and, although they don't then open, they remain fresh-looking on the bush for weeks. It hates cold wind, but will take a surprising amount of shade, forming an open, leafy shrub with soft red stems and red-tinged foliage, impervious to disease.

    I would not go as far as to say it is impervious to disease, but my impression is that it is relatively disease-resistant. I am truly enjoying the look and fragrance of this rose in my garden. Links to additional information:

    Roger's Roses
    UBC Botanical Garden
    An article by Valerie Easton in the Seattle Times

    Season All Season
    Date 2008-02-28
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    Keywords: Miscanthus, Ornamental grasses, Invasive plants

    PAL Question:

    I am looking for an ornamental grass that doesn't get over 5 feet tall and am wondering what are the growing conditions for Miscanthus sinensis (Gracillimus)? How much sun does it need, will it spread and invade my other plants, is it invasive in our area (Seattle)?

    View Answer:

    I found several cultivars of Miscanthus listed on the local web site Great Plant Picks. Miscanthus sinensis 'Morning Light' will reach about 5 feet tall by 4 feet wide. This Colorado State University Extension article on from ornamental grasses may give you additional ideas on grasses for your garden. Although the following link is for southwest Washington gardens, this Washington State University list of ornamental grasses may be of use. It includes Miscanthus sinensis 'Gracillimus,' and indicates it does not have a problem with self-seeding.

    Excerpt:

    Miscanthus
    BE CAREFUL! Many are self-seeding.

    M. sinensis 'Gracillimus' Maiden grass 4.5' FS Most popular. Seldom self-seeds.

    M. sinensis var. purpurascens Purple maiden grass, Flame grass 3 - 5' FS Gorgeous red-orange fall foliage. One of the earliest flowering varieties of maiden grass.

    M. sinensis 'Silberpfeil' Eulalia 4 - 5' FS One of the hardiest varieties of maiden grass.

    M. s. 'Morning Light' Dwarf maiden grass 4 - 5' S, LSh Arguably best all-around plant of the Miscanthus group. Blooms late with reddish flowers.

    M. s. 'Adagio' Japanese silver grass to 3.5' S, LSh Compact with silver-gray foliage. Two- to three-feet long panicles emerge pink, fade to white.

    M. s. 'Flamingo' Japanese silver grass to 6' Large, loosely open, pink-tinted inflorescences. Slightly pendant blooms appear late summer.

    M. s. 'Sarabande' to 6' Similar to Gracillimus, but finer textured. Golden copper colored inflorescences in August.

    M. s. 'Strictus' Porcupine grass 4 - 6' FS One of the hardier Miscanthus cultivars. Tolerates wet soils.

    M. s. 'Variegatus' Variegated silver grass 4 - 6' S, PSh Prefers moist, fertile, well-drained soil.

    M. s. 'Zebrinus' Zebra grass 4 - 8' S, PSh

    Update from 2012 on the invasive potential of Miscanthus cultivars:

    Wendy DesCamp of the Washington State Noxious Weed Control Board reports the following:
    "There is now a record of the plant growing in eastern Washington by the Columbia River in Benton County. [described as follows:] Shallow backwater on N shore of Columbia River . . . below McNary Dam, elev. 85 m, 45 degrees, 55.9 minutes N, 119 degrees 21.4 minutes west. Collected by Peter Zika, 17 June 2011.
    From what I can find, this is the first collection of naturalized Miscanthus sinensis collected in Washington."

    The State Noxious Weed Board is considering whether it should be added to the monitor list or not. The monitor list is a list of plants the Board is keeping track of to collect information and to see if the plants are occurring or spreading in Washington.

    UW Botanic Gardens Director, Professor Sarah Reichard had this to say about Miscanthus sinensis:
    "We have had it in the Soest Garden for years and I have not seen it invade and I am looking for seedlings. However, not invading in the artificial environment of a garden, with water and nutrient inputs means little for invasion in the wild. I have not heard of it being invasive here, and I have been paying attention to both this species and Imperata cylindrica.It might be a good addition to the [noxious weed] monitor list."

    Season All Season
    Date 2007-05-16
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    Keywords: Mosaic diseases, Tomatoes--Diseases and pests

    PAL Question:

    My unripe green tomatoes ('Old German' variety) have developed a very weird appearance: lots of lumps and bumps, and nooks and crannies, plus strange discolored blotches. What is causing this? And will I be able to salvage (and eat!) them?

    View Answer:

    There may be more than one problem here. I definitely see a physiological disorder called cat-facing in the photo you sent us. University of Massachusetts Extension provides this information about it:
    "Cat-facing is a physiological disorder of tomatoes. Cat-face originates in the early stages of flower bud development and is the result of abnormal development of plant tissue between the style and ovary which results in misshapen fruit. Other impediments to flower bud development can also result in cat-facing. The syndrome is related to unfavorable growing conditions, in particular several days below 60 F when the plants are young. High levels of soil nitrogen and excessive pruning aggravate the problem. Accidental exposure to phenoxy herbicides can also lead to malformed fruit. Cat face is more prevalent on large-fruited, fresh market tomato varieties. Good growing practices, especially temperature control, should be followed in greenhouse production of field transplants. Excess nitrogen, aggressive pruning, and accidental exposure to hormonal herbicides should be avoided."

    The book Epic Tomatoes by Craig LeHoullier (Storey Publishing, 2015) says that catfacing occurs more often in large varieties that also have large blossoms. Some older varieties (heirlooms) have this tendency. Plants put out in the garden when it is too cool can also develop this appearance later. And too much nitrogen worsens it. As early as the 19th century, plant breeders were attempting to breed out this characteristic in favor of more uniform, smooth-looking fruit, but many heirloom tomatoes much-sought for their flavor tend to have this bumpy look. A little bit of catfacing shouldn't render your tomatoes unusable. I have grown Cherokee Purple tomatoes that often have some cat-facing, but they are still delicious.

    Depending on the cause of the spots, the tomatoes may or may not develop to the point of ripeness and if they do, there may be some parts that rot and some parts which are still edible. Also depending on the cause, you may decide to pull out any affect plants and dispose of them.

    It's possible that those discolored spots are due to sunscald, but the pattern of the discoloration looks more like a virus. LeHoullier says that plants which are heavily pruned or have lost a lot of foliage are more vulnerable to sunscald. However, the discoloration on your tomatoes resembles a mosaic virus, such as tobacco mosaic virus. If you are growing Nicotiana in your garden, debris from that plant as well as tomato plant contact with any tobacco products (cigarettes, or the hands that have held them, etc.) could introduce the virus to your tomatoes through any small wound—such as a pruning wound or accidental damage to plant tissue.

    Washington State University Extension’s HortSense webpage has useful information on mosaic viruses as does University of Minnesota Extension.

    http://www.extension.umn.edu/garden/fruit-vegetable/plant-diseases/tomato-mosaic-virus-tobacco-mosaic-virus/index.html

    Still, the best thing to do is bring samples to your local Master Gardener Clinic. Many tomato problems look similar (viral, bacterial, stink bug damage, hornworm feeding). There is a good visual guide from Missouri Botanical Garden but an in-person diagnosis is best.

    Season Summer
    Date 2015-07-30
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    Keywords: Tree roots, Landscaping drain fields

    PAL Question:

    I have several sewer pipes that are getting plugged by tree roots on my grounds. I have used a rooter to remove the majority of the roots and know would like to detour their return by using a chemical called Root Free. It is a Copper Sulfate Pentahydrate. Is this product safe for my trees if used according to label?

    View Answer:

    Here is a link to information on this chemical from the Pesticide Action Network's database. This link leads to the Material Safety Data Sheet for Copper sulfate pentahydrate.

    This product is highly toxic to humans and aquatic life, but should not harm the trees. My question would be whether it makes more sense to remove entirely any trees with invasive roots, and replant with other plants whose roots will not cause trouble with the sewer pipes, rather than use copper sulfate. See information below from UGA College of Family and Consumer Sciences Cooperative Extension Service:

    Tree roots can enter sewage and drainfield lines and cause plugging of the lines. Lines should not be placed near trees, and trees should not be planted near lines. Remove tree roots mechanically or flush copper sulfate crystals down the toilet to help discourage or destroy the roots where the solution comes in contact with them. Some time must elapse before the roots are killed and broken off. Recommended dosage rates are two pounds per 300 gallons of tank capacity. No more than two applications per year are recommended. Time the application of copper sulfate to allow minimum dilution and maximum contact time. Copper sulfate will corrode chrome, iron and brass, so avoid contact with these materials. Used in recommended dosage, copper sulfate will not interfere with septic tank operation. Neither mechanical removal nor copper sulfate contact is a permanent solution for tree roots. Remove the trees for a permanent solution to the problem.

    Here are some links to more information tree roots and sewer lines and about planting on drain fields:
    Tree Roots vs. Sewer Lines from the city of Paso Robles, CA.
    Choosing Sewer Safer Trees
    Planting on Your Septic Drain Field

    And here are some suggestions for alternative plantings:
    Landscaping Your Drainfield

    If you do decide to go ahead and use the Root Free, by all means follow the directions to the letter, as it is required by law. You may want to check with Seattle Public Utilities Drainage and Sewer Maintenance to make sure that use of this chemical in the sewer system is permitted: 206-386-1800

    Season All Season
    Date 2007-05-16
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    Keywords: Failure to flower, Syringa

    PAL Question:

    I have a lilac bush given to me as a gift 13 years ago. I don't know the variety but the leaves look slightly different from the common lilacs I see. This bush has healthy looking leaves and while it has slowly put on growth over the 13 years it has never bloomed. I have tried adding ashes to the soil to make it more alkaline but nothing seems to work. What is the problem and how can I get this bush to bloom?

    View Answer:

    There are several reasons lilacs may fail to flower. Here is an excerpt from North Dakota State University Extension horticulturist Ron Smith in answer to a question similar to yours:

    Lilacs fail to flower because of insufficient sunlight, planted too deeply, too much nitrogen, improper pruning or winterkill of the flower buds. You said the lilacs get plenty of sunlight, but unless you used a lawn fertilizer to provide nutrients, it isn't likely too much nitrogen is the problem. If you planted too deeply, pull some of the soil back so the top of the roots are slightly exposed. If you pruned in July, then doing so removed the flower buds for the next growing season. If winter killed the flower buds, then hope for milder winters or purchase hardier lilacs.

    Colorado State University Extension's article, "Renewing Lilacs," offers other suggestions, such as late freezes, decreasing sunlight, and pest problems.

    Sunset's Western Garden Book (2001 ed.) says that annual pruning is needed for optimal flower production. Most lilacs bloom on wood formed the previous year, so they should be pruned just after flowering. Remove the spent blooms and cut back to a pair of leaves. There are a few lilacs which bloom on new growth, so it might be useful to know exactly what type of lilac you have. You could bring in photos and samples to our Herbarium for identification.

    Season All Season
    Date 2007-05-09
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    Keywords: Rubus, Fruit--Diseases and pests

    PAL Question:

    It appears that my raspberries may have a disease. I noticed some fruiting canes getting discolored, then curling leaves, then dying completely. I ripped out ones that were dying or dead, but others seem to be showing beginning symptoms.

    View Answer:

    There are many potential culprits that could be causing the problems you are observing with your raspberries. It could be a pest, or it could be a fungal disease. Remember that summer bearing raspberry canes die after bearing fruit. The canes start to look bedraggled even as fruit is ripening. Once all fruit has been picked these canes should be cut to the ground. Next year's fruiting canes will look healthy and should not be cut down to the ground.

    Have you looked inside any of the affected canes after cutting them? If you have cane borers, you may find that white grubs have burrowed toward the base of the cane. Crown borers also cause wilting of new growth in the spring followed by dieback of the cane. Here are links to information and images so you can compare what you are seeing with your plants:

    Insects and Diseases of Raspberries from University of Illinois Extension.

    Pests and Disorders of Blackberries and Raspberries from University of California.

    Washington State University's Hortsense page on Raspberries (see sidebar on left for diseases and insects)

    Raspberry root rot information is available in the Pacific Northwest Disease Management Handbook.

    Washington State University Extension's information for home gardeners says:

    "Foliage symptoms of root rots. Root rot is usually noticed when leaves begin to wilt, turn yellow or brown, and die. Symptoms commonly occur during warm spring or summer weather and may develop in a few days or take longer. If longer, leaves are generally yellowish and stunted before they die.

    "Root symptoms of general root rot. Root systems are small, dark brown or black, and rotted. Since healthy roots may or may not have dark surfaces, determine root condition by cutting or scraping them. All of the inside of a healthy root is whitish, but the inside of a rotted root is partly or entirely brownish or blackish. Wash the cutting tool in soapy water and swab in rubbing alcohol after cutting."

    You may want to bring samples plus photos of the whole plant to a Master Gardener clinic for diagnosis. There is a link to the current clinic schedule on their website.

    Once you have identified the source, you can try to address the problems and resume growing happy raspberry plants. Oregon State University has a guide to growing raspberries which may be helpful.

    Season All Season
    Date 2007-05-26
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    Keywords: Vitis, Propagation

    PAL Question:

    I am having difficulty propagating Vitis coignetiae. The cuttings are not taking. Any advice?

    View Answer:

    Here is what I found in the Plants for a Future Database:

    Seed - best sown in a cold frame as soon as it is ripe. Six weeks cold stratification improves the germination rate, and so stored seed is best sown in a cold frame as soon as it is obtained. Germination should take place in the first spring, but sometimes takes another 12 months. Prick out the seedlings into individual pots when they are large enough to handle and grow them on in a cold frame for their first winter. Plant out in early summer.

    Cuttings of mature wood of the current seasons growth, December/January in a frame. These cuttings can be of wood 15 - 30cm long or they can be of short sections of the stem about 5cm long with just one bud at the top of the section. In this case a thin, narrow strip of the bark about 3cm long is removed from the bottom half of the side of the stem. This will encourage callusing and the formation of roots. Due to the size of these cuttings they need to be kept in a more protected environment than the longer cuttings. Cuttings are difficult from this species.

    Layering: This is the best method for this species.

    See the Royal Horticultural Society for general layering information.

    Season All Season
    Date 2007-05-31
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    Keywords: Symphoricarpos albus, Transplanting

    PAL Question:

    I need to move some established snowberry shrubs forward about 8 feet to make room for a large 7' propane tank. I'm hoping to salvage the snowberry shrubs which are currently in a mostly shady location and would continue to be in shade after I move them. (I'm hoping they will block the view of the propane tank. Do you have any tips on transplanting this type of shrub? Or is it too difficult to do once they have reached 5+' tall? Am I better off starting with smaller snowberry that are only 3' in height?

    View Answer:

    According to the following information from University of Connecticut's Plant Database, snowberry or Symphoricarpos albus, is easily transplanted.

    From an Olympia nursery catalog, Sound Native Plants:

    Symphoricarpos albus - Snowberry
    Exposure: full sun to shade
    Soil moisture: very moist to dry
    Transplanting success: high
    Growth rate: rapid
    Form: deciduous shrub to 2-6 feet; fibrous, shallow root system, spreads vigorously by suckers

    Snowberry is an incredible survivor, flourishing in situations that would slay a lesser plant. It transplants well, tolerates sun or shade, withstands drought and/or occasional flooding, and spreads quickly even in poor soil or on steep hillsides. Another plus for snowberry is that it is one of the few native shrubs that stays small--it averages three or four feet tall--and thus is a good choice for areas where view corridors are important. Hooray snowberry!

    If it makes it easier for you to move the plants, you can prune them back (this is usually done in spring). If individual plants have grown into a dense mass of stems, you can also dig up each whole plant and only replant smaller pieces of it.

    Season All Season
    Date 2007-06-02
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    Keywords: Hibiscus, Topiary work, Pruning

    PAL Question:

    I have a small hibiscus that I would like to train into a tree with the twisted trunk and I have no idea how to go about that. Please advise.

    View Answer:

    When you prune your hibiscus into a tree-like form with a single trunk, it is called a standard. There are even braided topiary forms. To achieve the twisted shape, you will probably need to create a support or frame.

    The following general information on pruning comes from Tropical Hibiscus:

    "While the tropical hibiscus can be pruned any time, probably the ideal is the earliest where the resulting tender new growth will be safe from cold damage*. For shaping purposes, some growers will prune the longest third of the branches and return in 4 to 6 weeks and prune the next longest third. Only sharp, clean shears should be used. A clean cut should be just above and angled down and away from an 'eye' or node. (A node is the junction of a leaf and the stem. There is a small bud in this junction that is activated after pruning.) Cutting above outward pointing "eyes" will encourage growth in that direction. The new growth resulting from pruning invigorates the plant and will provide a source for many new blooms."

    The American Horticultural Society's Pruning & Training (edited by Christopher Brickell and David Joyce, DK Publishing, 2011) describes the technique for creating a braided stem:
    "Form a braided stem simply by braiding together three flexible young shoots. Select the strongest three on a multistemmed young plant, and remove the remainder. Single-stemmed plants can be cut back hard to produce multiple stems."
    The book also describes what is called a "barleysugar stem," which may be more like the twist or spiral you envision: in this technique, "use a sturdy wooden pole with dowel pegs inserted in a spiral along its length. Train one or two stems around the pole, holding them in place by looping them beneath the dowels. Remove the pegs and the pole in sections when stem growth has hardened."

    Here is a link to Brooklyn Botanic Garden's article on espalier forms, Special Cases: Pruning for Particular Purposes.

    The Miller Library has a good selection of books on pruning and training, and specifically on topiary. You can search the library's catalog by clicking this link.

    Season All Season
    Date 2007-06-06
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    Keywords: Vegetable gardening, Container gardening

    PAL Question:

    My question is about the ceramic pots that you see in nurseries and places in the area. The pots are glazed on the outside, and unglazed on the inside, and they are made in China and Vietnam. Are these pots safe for planting vegetables and herbs? Or, are there materials in the interiors of the pots that could leach into the soil and make the vegetables and herbs unsafe to eat?

    View Answer:

    Some ceramic glazes do contain toxic materials, such as lead and cadmium. Washington State Department of Health has information on preventing lead poisoning, and on testing for lead.

    State of Oregon's Lead Poisoning Prevention Program includes information on sources of lead exposure, including pottery.

    California Department of Health has several pages on toxins in pottery.

    Excerpt:

    "The U.S. Food and Drug Administration (FDA) sets standards at the national level for the amount of lead that can pass out of, or 'leach,' from dishes. Tableware with lead levels greater than these standards cannot legally be sold in the U.S. The FDA regulations cover only tableware that is imported or that is brought into the state for sale. The standards apply only to items that are used for foods and beverages. They do not apply to pieces that either cannot hold liquids or are not intended to hold liquids, such as salt shakers, cookie jars, butter dishes, etc. See the table below for the FDA standards for lead in ceramicware.

    Decorative ceramics
    The FDA has labeling rules for ornamental or decorative ceramics that are not intended for food use. These items must either (1) be permanently labeled with a logo or statement that they are unsuitable for food use, or (2) be made incapable of holding liquid. If an item is clearly intended for food use, such as a bean pot, labeling it is not sufficient, however. It must be made unusable, for example, by having a hole drilled through any surface that could hold liquid."

    My co-worker tells me that some retail stores are good about informing customers if pots are unsafe for food use. This document from Clemson University Extension (although its focus is cookware) suggests that you not use pottery which does not bear the label, "Safe for Food Use:"

    If a pot has been fired at a high temperature (something you cannot easily ascertain by looking at it), my thought would be that there would be less likelihood of toxic material from the glaze leaching inward, but if the clay itself comes from a source which is full of contaminants, there may be a risk apart from the glaze. If you are at all concerned about using these pots for growing food, my advice would be not to do it. There are other ways of growing food in containers, such as untreated wood boxes or barrels. See links here for general information on growing vegetables in containers:

    Vegetable Gardening in Containers from Virginia Cooperative Extension.
    Container Vegetable Gardening from North Carolina State University.

    Season All Season
    Date 2007-06-02
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    Keywords: Horticultural oil, Apples--Diseases and pests

    PAL Question:

    I have a dwarf Braeburn apple tree that gets spotted apples every year. The leaves drop off and the apples are stunted and not edible. I am spraying with dormant oil spray per the instructions and it looks beautiful right now. I need to know how often to spray it and how long into the season. The instructions aren't clear on this. Also, does the dormant oil spray make the apples unsafe to eat at all?

    View Answer:

    Here is what Michael Phillips says in his book, The Apple Grower: A Guide for the Organic Orchardist (Chelsea Green, 1998): "Oil sprays smother the overwintering eggs and emerging nymphs of a number of foliar feeders. Use of a highly refined oil is tolerable in an organic orchard, but generally not necessary." He recommends encouraging beneficial insects to control aphids. Aphids may be a sign of a deeper imbalance that needs addressing.

    Whether the dormant oil spray makes the fruit unsafe to eat depends greatly on what the oil is made of: many such sprays are petroleum-based and would therefore not be safe. See the following information formerly available online from BeyondPesticides.org:

    Excerpt:

    "Most horticulture oils used today are petroleum based (Grossman 1990), yet a growing number of horticulture oils are being made with vegetable oils, which are considered a least toxic pesticide. Carefully read the label or ask your pest control service provider to determine if the horticulture oil is vegetable or petroleum based."

    From Washington State University Extension agent Mary Robson:

    "How Do I Use Dormant Sprays?"

    "Neither the spray nor the applicator is dormant in a 'dormant spray': the plants to which it's applied are. The term refers to winter-applied sprays for insect pests and diseases, put on before foliage begins to leaf out.

    "To use dormant sprays, first identify the reason for the spraying. They are often used on fruit trees to control over-wintering insect pests such as scale and aphids. (The aphids over-winter as eggs, and the spray smothers the eggs, preventing spring hatching.) A dormant spray isn't an all-purpose winter splashing of pesticide around the garden: it's a specific spray chosen for a specific pest. The dormant spray used on fruit trees is often horticultural oil (sold as superior-type oil), and it may be mixed with lime-sulfur depending on the pest to be controlled. It's sprayed thoroughly to give good coverage on the trunk, branches, small limbs and shoots.

    "Because dormant sprays are generally applied early in the season, they tend to be less disruptive to beneficial insect predators and parasites which aren't in active life stages in mid-winter. While generally used in fruit tree maintenance, dormant oil sprays are helpful for landscape plants with similar aphid or scale problems. Ornamental plums (purple-leaf plums) often suffer from infestations of aphids or scale; if that's been the case, a dormant oil spray may help reduce the populations."

    The following two links are from the Colorado State University Cooperative Extension. Insect Control: Horticultural Oils and Pest and Disease Control Using Horticultural Oils. Excerpt:

    "Most horticultural oils contain naphthene and paraffin compounds. Paraffins are valuable to gardeners because they're more toxic to insects and less toxic to plants than other oil compounds. In contrast, oils containing naphthene are less pesticidal and more likely to injure plants than paraffinic types. Oils high in naphthene also contain more impurities such as phytotoxic aromatic and unsaturated hydrocarbons. However, the newest horticultural oils contain only tiny amounts of those compounds."

    Have you determined what the cause of the spotting on your apples is? Might it be apple scab? In case that is what you have been seeing, here is what Washington State University Extension says:

    "Apple scab is caused by a fungus which also causes scab on crabapple and hawthorn. The first infections occur during wet weather in the spring. Initially, the disease causes tiny, pale, chlorotic, water-soaked spots on the leaves. The spots enlarge and darken to a dark, velvety, olive-green then to black. Leaves may become distorted, puckered, and mottled. Leaves may drop, sometimes resulting in severe defoliation of susceptible trees. Scab can also affect fruit. Fruits infected early in development show olive-green to brown, roughened or corky spots which may develop deep cracks. These apples are often misshapen. Fruits infected at later stages develop small black "pinpoint" scab spots while in storage. The disease is favored by cool, wet conditions and overwinters in infected plant debris.

    "Management Options:

    "Select Non-chemical Management Options as Your First Choice!!

    • Avoid overhead irrigation.
    • Plant in full sun.
    • Plant scab-resistant varieties such as 'Akane', 'Chehalis', 'Liberty', 'Paulared', 'Prima', or 'Tydeman Red'.
    • Rake and destroy (do not compost) fallen leaves, or cover them with soil.
    • Space plantings and prune to provide good air circulation and light penetration.
    • The application of nitrogen to the leaves in the fall will enhance the decomposition of the fallen leaves."

    The following website is for large-scale growers, but may have information of interest to you:
    Disease Management Guidelines for Organic Apple Production in Ohio

    Season All Season
    Date 2007-05-23
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    Keywords: Flowering cherries, Pruning trees

    PAL Question:

    I live in Seattle. My condo board is having a debate about whether pruning an ornamental cherry after May will kill it or not. Can you help? Also, when should it be pruned?

    View Answer:

    According to Cass Turnbull of the local organization, Plant Amnesty, the main reason pruning ornamental cherries is problematic is that the branch system of these trees is complex, and it is hard to tell (if you are not an experienced gardener or a professional arborist) what to prune. In her Guide to Pruning (Sasquatch, 2006), Turnbull says that ornamental cherries are prone to dieback if their branches are shortened. Besides the dieback issue, improper pruning can give rise to watersprouts (the branches grow straight up). I consulted two other pruning guides, both of which advised against any pruning of ornamental cherries.

    Do you know why the board wants to prune these trees? If the trees are too large for the site, it might make more sense to remove them and plant something appropriate which will not require risky pruning. You may find this discussion forum from University of British Columbia Botanical Garden helpful.

    Excerpt:

    "These generally disease susceptible trees resent severe heading back. Trying to force it to become a perfectly symmetrical shape will also destroy its natural character; much of the appeal of aged Japanese cherries (and related trees) is the contrast between the prettiness of the flowers and the rugged appearance of the trunk and branches."

    My summary is that, while pruning the trees may not kill them outright, it could make them aesthetically unappealing and more susceptible to disease, so it would be best to let them be.

    Season All Season
    Date 2007-05-26
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    Keywords: Vegetable gardening, Pesticides and the environment, Pesticides

    PAL Question:

    How soon I can plant my edibles after I've used weed and feed?

    View Answer:

    Do you know which weed and feed product was used? That would help in determining the chemical's half life (persistence) in the soil. Regardless of which chemical was used, my recommendation would be not to plant any edibles in a site which has been treated with weed and feed, but to find another location for your food plants (such as containers made of safe materials, or raised beds with a barrier between the bed and the chemically treated area of the garden).

    Local garden writer Ann Lovejoy has discussed weed-and-feed products in her column. Here is a link.

    Here is what retired Washington State University Extension agent Mary Robson had to say on this subject in one of her columns no longer available on-line:

    Just one note of caution-be careful with all chemicals. Many pesticides ordinarily used in gardens are not allowed on edibles. An example is Lawn Weed and Feed which will harm any broadleaf plant whether lettuce or marigold or petunia. It's probably safest to keep pesticides out of the garden if you plan to eat the produce.

    From Washington Toxics Coalition:

    The Hazards of Weed and Feed

    "Weed and feed is a mixture of lawn fertilizer with weed killer, usually 2,4-D and related compounds. The problem with weed and feed is that it is designed to be applied to the entire lawn regardless of whether or not weeds are actually present. This encourages over use. For example, if 30% of your lawn is covered in weeds, 70% of a weed and feed application will be wasted, since the herbicides have no residual action. Since many people do not realize that weed and feed is a pesticide, they may be less inclined to read an follow label instructions. For example, did you know that it is illegal to apply weed and feed more than twice per year on the same site?

    "The herbicides in most weed and feed products are mobile in soils and are widely found as pollutants in local streams, according to the U.S. Geological Survey. In addition, 2,4-D is neurotoxic and may be a carcinogen according to some studies.

    "Weed control should be practiced only as needed, not every time you fertilize. Mechanical controls are preferable to protect health and the environment. If chemical controls are used, spot treatment should be utilized to minimize product use and resultant risks from direct exposure and track-in to the home on shoes and feet."

    Here are links to information on some common weed-and-feed type products and their hazards:

    From the Pesticide Action Network North America

    From the Winter 2005 (updated April 2006) article in Journal of Pesticide Reform

    Season All Season
    Date 2008-02-07
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    Keywords: Blechnum spicant, Acorus, Adiantum pedatum, Carex, House plants

    PAL Question:

    I've taken up planning plants for our office, and wondered if you could give advice. I'm looking for Northwest native plants that would be happy indoors, in an office environment. Available sunlight will vary by spot but is generally low (but I can probably swing some plant lights); air is standard low-humidity commercial-building air.

    View Answer:

    Most Northwest native plants I can think of are not ideal for growing indoors. However, I asked my colleague who used to garden for the Seattle Public Library, and she says that the library is growing native species of ferns indoors. She notes that they are especially prone to pests (whitefly) and diseases (scale), and must be watered every day.

    Below is the list of plants being grown in the main (Central) library branch:

    • Acorus
    • Blechnum spicant
    • Adiantum pedatum
    • Carex elata 'Bowles Golden'(tall)
    • other fern (Rumohra adiantiformis?)

    I hope this helps. If you wish to reconsider using natives in favor of more traditional choices for indoor plants, there are many more choices available. Below are a few links that may be use to you:

    Low Light Houseplants from University of Vermont Extension

    Growing Indoor Plants with Success from University of Georgia Cooperative Extension

    Interior Plants: Selection and Care from University of Arizona Cooperative Extension

    Season All Season
    Date 2007-06-08
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    Keywords: Moss gardening, Mosses, Lawn alternatives

    PAL Question:

    Could you tell me how to replace grass with moss in the shady areas of our lawn?

    View Answer:

    There are a number of options for replacing the grass in the shady part of your garden. Should you decide to cultivate moss, Oregon State University's page on Encouraging Mosses should be of interest.

    There are two books I would recommend, Moss Gardening by George Schenk (Timber Press, 1997), particularly the chapter on "Moss Carpets," and How to Get Your Lawn Off Grass by Carole Rubin (Harbour Publishing, 2002). Rubin gives directions for preparing your site, which involve digging out existing plants or smothering the lawn with mulches of leaves (12 inches), bark (3 inches), or newspaper (10 sheets thick). Schenk offers several different methods for creating a moss garden. Briefly paraphrasing, these are:

    1. Work with nature, allowing self-sown spores of moss to take hold. (Prepare the site by weeding, raking, and perhaps rolling the surface smooth).
    2. Encourage the moss in an existing lawn by weeding out grass. You can plant what the author calls "weed mosses" which will spread, such as Atrichum, Brachythecium, Calliergonella, Mnium, Plagiothecium, Polytrichum, and others.
    3. Instant carpet: you can moss about 75 square feet if you have access to woods from which large amounts of moss can be removed legally.
    4. Plant moss sods at spaced intervals (about one foot apart) and wait for them to grow into a solid carpet.Choose plants that match your soil and site conditions.
    5. Grow a moss carpet from crumbled fragments. This is rarely done, and only a few kinds of moss will grow this way, including Leucobryum, Racomitrium, and Dicranoweisia.

    In her book Big Ideas for Northwest Small Gardens, Marty Wingate recommends Mazus reptans. It is semi-evergreen to evergreen with tiny blue flowers from late spring through summer. It takes full sun to part shade and is delicate looking, but takes foot traffic. It requires some fertilizer to stay perky. Another source of ideas is the website www.stepables.com. Click on "plant info," then "plant search."

    Another ground cover that can take foot traffic is Leptinella gruveri "Miniature Brass Buttons."

    Season All Season
    Date 2007-06-08
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    Keywords: Clematis

    PAL Question:

    I have a beautiful clematis in full bloom right now. Do I need to dead head the spent blooms to make it bloom again? It is Clematis Candida.

    View Answer:

    In researching this question, I used Raymond Evison's excellent 1998 book, The Gardener's Guide to Growing Clematis. Your Clematis lanuginosa 'Candida' is considered a mid-season, large-flowered type, and it often reblooms, according to Evison. In the chapter on cultivation, he says, "Some clematis growers prefer to remove spent flowerheads to encourage further crops of flowers, especially with the early large-flowered single, double, and semi-double clematis. Certainly, if the old flowers are removed with a length of stem with 2-3 nodes, new growth will appear and a further crop of flowers will be produced. When this is done, it is important to keep the clematis well watered and fed. The only drawback...is that the attractive seedheads on this group of clematis will be lost. A compromise can be achieved by removing only 50 per cent of the spent flowerheads..."

    Season Summer
    Date 2007-06-11
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    Keywords: Zamia, Poisonous plants, House plants, Cycads

    PAL Question:

    I am interested in finding out if someone there can tell me the proper culture for Zamia furfuracea. I just acquired one that had been potted up as a bonsai and put on sale at a local grocery store. I think they may not have known or cared what it was. This is a plant I grew outdoors when I lived in California. I'm wondering what to do with it in Vancouver, WA. The options are greenhouse, patio pot, indoors, outdoors.

    View Answer:

    I found general cultural information from Florida State University Cooperative Extension. This is a zone 9b-11 plant, and your area is probably about zone 8, so I think you would want to grow this with some protection.

    University of British Columbia Botanical Garden's discussion forum describes this as an indoor plant. This article in the journal of University of Arizona Cooperative Extension is about a similar plant, Zamioculcas zamiifolia, often confused with Zamia furfuracea.

    Richard Langer's book, Grow It Indoors (Stackpole Books, 1995) says to grow this "handy table-sized cycad" in temperate partial sun with humusy soil that is kept constantly moist.

    Another thing to keep in mind if you are growing this plant around pets or small children is its toxicity. The ASPCA lists this plant as toxic. Dr. Nelson's Veterinary Blog has an article entitled "Sago palms are poisonous to animals."

    Season All Season
    Date 2007-06-08
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    Keywords: Tsuga heterophylla, Trees--Diseases and pests

    PAL Question:

    My Western Hemlock is infested with woolly adelgid. Help! How can I save my tree?

    View Answer:

    The USDA Forest Service has an entire web site devoted to this pest problem, and includes information on different ways of managing the Hemlock woolly adelgid.

    The most effective approach is prevention, as treatment tends to be expensive and is not always effective. Information from University of Maryland Extension does describe the use of dormant oil spray in late winter and summer application of horticultural oil and insecticidal soap, but care must be taken to cover the entire tree. Also, it is important to avoid the use of nitrogen-heavy fertilizers which create a lot of succulent new growth attractive to the pest.

    I recommend that you consult a certified arborist for advice on how to save your (Western hemlock). You can obtain referrals from Plant Amnesty or you can select an arborist from the Pacific Northwest Chapter of the International Society of Arboriculture.

    Season All Season
    Date 2007-06-13
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    Keywords: Prunus, Fruit--Diseases and pests

    PAL Question:

    For three years, my plum tree has had leaves that curl and shrivel somewhat. I have heard of aphids causing leaf curl in plums, but I don't see many aphids.

    I also have a peach tree that has "Peach Leaf Curl" or Taphrina deformans and the symptoms on the plum leaves look similar to that. Here is what I wonder:

    • The peach and plum are at least 100 yards apart. Is it really possible that the peach infected the plum?
    • With the peach tree the fruits are also affected but with the plum fruits do not appear to be affected.
    • Are peach and plum affected by the same diseases?

    View Answer:

    Both peach and plum trees are in the genus Prunus. Your plum tree's problem sounds like plum pockets and peach leaf curl, which are caused by fungus (usually Taphrina).

    From Iowa State University Plant Pathology:
    Have you noticed lately that your peach leaves appear curled or puckered? Do leaves appear to be lighter than normal, flushed with red, blistered, distorted, and curled? Chances are your tree has peach leaf curl, a fungal disease caused by Taphrina deformans. Although peach leaf curl is primarily a disease of peach, nectarines are also affected. Peach leaf curl is first noticed in spring when young leaves start to emerge. The entire leaf or a portion of it may appear crinkled and curled with flushes of red or purple . Later on in the season, the fungus begins to produce spores and leaves appear silvery or powdery gray. Infected leaves turn yellow and brown and fall off the tree and are replaced by a new set of foliage. Flowers, young fruits and stems may also be infected. Affected fruits are distorted with wrinkled, discolored areas on the surface. Extensive defoliation may affect fruit yield the following year and may also predispose the tree to winter injury and other diseases.

    Plum pocket is a disease in plums caused by Taphrina communis. Leaf symptoms are similar with peach leaf curl and the plums appear to be distorted, wrinkled, and puffy. This disease is not considered a serious problem in most commercially cultivated plum varieties.

    Here is Oregon State University's online guide to plant diseases. This is Washington State University's comparable site.

    I don't know if your plum could have gotten the same species of Taphrina fungus that is affecting your peach (i.e., Taphrina deformans), but the conditions in our climate are probably ideal for this type of fungal disease. University of California, Davis says that the pathogen which causes peach leaf curl survives on tree surfaces and buds, and is enhanced by wet spring weather.

    From University of Nebraska Plant Pathology:

    Plum Pockets is very similar to the well-known disease peach leaf curl. It reached epidemic proportions on plum in the 1880's and sand cherry in the 1940's. The disease is still common today but rarely has an economic impact on stone fruit production. However, its unique symptoms always seem to peak the interest of individuals who are seeing it for the first time. The disease is caused by two species of Taphrina. Taphrina communis (Sadelbeck) Giesenh. has a worldwide distribution. Its hosts include plum (Prunus angustifolia) and several wild Prunus spp. found in America. Taphrina pruni primarily infects European plums and is rarely found in America. The disease cycle of Taphrina communis is similar to that of Taphrina deformans (peach leaf curl). The fungus overwinters as conidia on twigs and bud scales. Infection generally begins at bud break when these spores are rain splashed to susceptible green tissue. Leaves, shoots, and fruit are all susceptible but symptom development is most common on fruit. The fungus invades host tissue directly through epidermal cells. Once the fungus is established, a specialized mat of fungal cells (hymeneal layer) containing asci and ascospores forms. The asci are not protected by a specialized ascocarp. Ascospores are released, germinate and begin budding, much as a yeast does. Conidia (bud conidia) serve as secondary inoculum in the spread of the disease. Initiation of the disease cycle is favored by cool wet weather.

    You might consider bringing in samples of the affected leaves to a Master Gardener Clinic for a definitive diagnosis. They may also have more information on whether the disease can pass from peach to plum, or whether your two types of trees simply have two different strains of the pathogen.

    Season All Season
    Date 2007-06-13
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    Keywords: Chenopodium quinoa

    PAL Question:

    What is quinoa, botanically? Is it a grain, or something else?

    View Answer:

    The botanical name for Quinoa is Chenopodium quinoa. According to information from the Alternative Crops Manual produced by University of Wisconsin Extension, it is an annual plant in the goosefoot or Amaranthaceae family, which also includes the familiar weed, lambs' quarters or Chenopodium album. This article states that "Quinoa is sometimes referred to as a 'pseudocereal' because it is a broadleaf non-legume that is grown for grain unlike most cereal grains which are grassy plants. It is similar in this respect to the pseudocereals buckwheat and amaranth." Edible: An illustrated guide to the world's food plants (National Geographic, 2008) states that true cereals are members of the Poaceae or grass family, but quinoa more closely resembles spinach. It was first used as a food plant around 5000 B.C.E. near Lake Titicaca in the Andes, where it is native. Its common name in that region is "the mother grain."

    Incidentally, the Food and Agriculture Organization of the United Nations declared 2013 the International Year of Quinoa, "recognizing the Andean indigenous peoples, who have maintained, controlled, protected and preserved quinoa as food for present and future generations thanks to their traditional knowledge and practices of living well in harmony with mother earth and nature."

    Season All Season
    Date 2013-03-13
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    Keywords: Cucumis melo, Cross-pollination, Citrullus lanatus, Cucumis sativus

    PAL Question:

    Will watermelon and cantaloupe cross-pollinate and produce bad-tasting melons? Is it possible for a vine that had cucumbers growing on it earlier in the season to produce a cantaloupe? I could swear that we now have what looks like a melon on a vine that had cukes before...

    View Answer:

    The short answer is, no. It's fine to grow watermelons and cantaloupe side by side. Cross-pollination between melon varieties may occur, but not between watermelons (Citrullus lanatus v. lanatus) and cantaloupes (Cucumis melo ssp. melo v. cantalupo), as they are two different species. In addition, cross-pollination affects not the melon produced that year, but the melons one might grow from any seeds produced inside that melon. According to Sue Stickland's Back Garden Seed Saving (Chelsea Green, 2001), "commercial seed growers are recommended to isolate melon varieties by 500-1000 meters" or "bag and hand-pollinate the flowers" to keep unwanted hybridization from happening.

    The same principle holds true for cantaloupe (Cucumis melo and cucumber (Cucumis sativus): they are indeed in the same plant family (Cucurbitaceae), but they are different species. If your vines were planted close together, you night not have realized there was a melon developing in among the cucumbers--and if you planted the vines from seed, it's very possible the seed packet contained a surprise cantaloupe!

    You may find this information from Iowa State University Extension about cross-pollination among vine crops interesting:
    "Since they have a similar flowering habit, bloom about the same time, and are members of the same plant family, it is logical that gardeners might assume that squash, melons, and cucumbers will cross-pollinate. Fortunately, however, this is not true. The female flowers of each crop can be fertilized only by pollen from male flowers of the same species. Cross pollination, however, can occur between varieties within a species."

    An article on fruit set in the Cucurbit family from University of California, Davis (which also has information on how to hand-pollinate plants when necessary) says much the same thing:
    "A common misconception is that squash, melons, and cucumbers will cross-pollinate. This is not true; the female flowers of each can be fertilized only by pollen from that same species. Varieties within each species, however, will cross-pollinate."

    Season All Season
    Date 2012-05-10
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    Keywords: Wisteria

    PAL Question:

    We have a Chinese Wisteria which we've had for 20 years. We've trained it on a trellis to the side of our covered porch and then on a rope across the front so there is a nice green, leafy fringe along the porch front. However, this plant has never bloomed.

    We have consulted with our local horticultural experts and they have suggested various treatments. The lawn care people do not fertilize near the roots of the wisteria so it doesn't get too much phosphorus, we have done root pruning, we have even hit the trunk with a board to shock it, have applied super phosphate but no blooms. We get some pretty cold winters, but I've never even seen flower buds anywhere on the plant. I know wisterias are sometimes late in blooming, but this is a long time to wait! The roots of the plant face east and get lots of sun. The part across the porch is shaded in the afternoon because we have two pine trees in the front yard. We prune off the tendrils that form during the summer to keep the plant in check, but what else can we do to get blooms? I know it would be a spectacular display if it ever bloomed and have almost given up trying. I'm thinking of hanging artificial blooms just to get the effect!

    View Answer:

    I found quite a bit of discussion in online gardening forums about flowerless wisterias, so you are not alone. You may find this information from Cass Turnbull of Plant Amnesty helpful:

    "THE MOST COMMON COMMENT I get at classes and at the PlantAmnesty educational booth is, "My wisteria won't bloom." It is natural for these vines to take between three and seven years to start blooming. I have read that frequent, proper pruning may help them to begin blooming sooner, or at least more. On the other hand, some people have old vines that have never bloomed. I am told that these are seed grown plants or "mules." I have often heard root pruning recommended to force an older vine to bloom. Basically, this means that you use your shovel to cut the roots in a circle (or dotted circle) a foot or two from the vine. I have also heard people recommend fertilizer formulated to encourage blooms, (not heavy on nitrogen). However, I have been faced with such a vine and had no luck with either technique. In that case, as with all non-performers, removal is the best option, and no one will blame you for it."

    Here are gardener Ketzel Levine's comments, from her NPR.org site:

    "Depending on how old your wisteria is, do know that young plants can take up to eight or ten years before they flower, especially if started from seed. Other reasons wisteria fail to bloom: lack of adequate sunlight (needs at least six hours of full sunlight); too much nitrogen fertilizer (causes more vegetative growth); pruned heavily in winter or spring (also encourages vigorous vegetative growth); severe winter injury/cold-blasted flower buds (though that is clearly not a problem this year) or a bum plant. It happens."

    You could either try the method described above, of cutting a circle with a shovel, or you could replace the vine, or you could follow through on your artifical flower idea! (I've heard that Bellevue Botanical Gardens hangs Wisteria-shaped lights from their arbor for their holiday light show.)

    Season Summer
    Date 2007-06-13
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    Keywords: Hippophae

    PAL Question:

    I am wondering about whether or not sea buckthorn grows here in Washington, if you have examples of it at the arboretum, or if anyone here sells the tree or the berries/extracts. A Ukrainian friend told me about the health benefits of the berries, and I was curious as to whether sea buckthorn can be found in Washington state.

    View Answer:

    Washington State University's Fruit Research Station in Mount Vernon has been growing sea buckthorn, or Hippophae rhamnoides, in its fruit trials. Below are the varieties they grew:

    Sea Buckthorn (Seaberry)
    'Frugana'
    'Hergosa'
    'Leikora'
    'Pollmix' male
    'Russian Orange'

    Page 16 of this WSU publication includes the results of the trials:

    "Sea Buckthorn (Hippophae rhamnoides) is a very thorny shrub or small tree native to eastern Europe and Asia. It has nitrogen fixing properties and is very tolerant of drought and poor soils, so has been introduced as a shelter belt plant in some of the plains States and Canada. In eastern Europe and the former Soviet Union the berries are commonly harvested for juice, which has nutritious and other healthful properties. Medicinal uses of extracted plant oils are also well documented in Europe and Asia. Plants on trial at Mount Vernon have fruited very successfully for the past 3 years, and appear quite well adapted horticulturally. The plants are very productive, setting many small orange fruits with a citrus like flavor. The juice is high in vitamin C. We have not had any problems with pests thus far and this shows great potential for organic growing. The commercial potential of this plant is being pursued by the British Columbia Sea Buckthorn Growers' Association, in the Okanagan Valley. Information on the Association and on sea buckthorn is available from Okanagan Sea Buckthorn. More information in a paper on the fruit potential of sea buckthorn by Thomas S.C. Li from the Summerland, B.C. fruit research station."

    According to Arthur Lee Jacobson's Trees of Seattle (2006), there is a specimen in the Washington Park Arboretum, but it may be easier to locate the 19-foot example at the Good Shepherd Center on the south wall of the annex (see directions to Seattle Tilth) There are others at Meadowbrook Park, and individual residences at 4015 NE 70th St., and 208 NE 42nd St. You might also ask the manager of the U.W. Medicinal Herb Garden if he has grown it: Keith Possee, UW Medicinal Herb Garden 206-543-0436, 543-1126; kpossee@u.washington.edu.

    From the Raintree Nursery catalog:

    "Perhaps the most widely grown, northern hardy, fruiting plant in the world and most Americans have never heard of it. Incredibly productive and great for your backyard. This attractive small tree or shrub from the Russian Far East has narrow silver leaves. It grows from 6-10' tall with a narrow upright growth habit. Space 7' apart or 3-5' for a hedge. It is extremely hardy, to -50 F. It is disease resistant and easy to grow. Plentiful round yellow orange fruits cover the female plants making them beautiful edible ornamentals. Branches are used in florist displays. Commercial crops are harvested by cutting off entire fruit laden branches. Very high in Vitamin C, ln Europe the fruit is made into sauces or jellies and as a base of liqueurs. The juice is sour and has an orange passionfruit like flavor when sweetened. Blended with other fruits, or by itself, it makes a delicious juice. It is also used widely in Europe and Asia as a healing oil and for other medicinal purposes."

    Season All Season
    Date 2007-06-14
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    Keywords: Chionodoxa, Vancouveria hexandra, Tiarella, Pulmonaria, Galium, Brunnera, Vinca, Epimedium, Lamium, Platanus, Narcissus, Liliaceae, Geranium

    PAL Question:

    We have a very large beautiful sycamore in our back yard. My roommate thought it would be nice to build a flower garden around the base of the tree, but something tells me that doing so would be harmful to the tree's root system. Is this true? I would love to hear your thoughts.

    View Answer:

    I think it should be safe to plant shallow-rooted, shade- and drought-tolerant perennials and small bulbs under your sycamore (I'm assuming you mean Platanus species, and not sycamore maple, which is Acer pseudoplatanus). You just need to be careful not to pile soil on top of any exposed roots, and try not to scrape or scuff any roots when you are planting. This tree does have spreading roots so they may extend out some distance. More information about the tree can be found on the pages of the U.S. Forest Service.

    Some of the plants which may work well in your garden are:

    Brunnera macrophylla
    Epimedium
    Galium odoratum
    Geranium phaeum
    Lamium (but not the invasive Lamium galeobdolon)
    Pulmonaria
    Tiarella
    Vancouveria hexandra
    Vinca minor
    Chionodoxa
    Narcissus
    Scilla

    Season All Season
    Date 2007-06-16
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    Keywords: Cryptomeria

    PAL Question:

    My Black Dragon Japanese Cedar has a lot of dead branches. The tree is healthy otherwise. A foot of new growth this year. The nursery told me this was normal. Can you give me an opinion?

    View Answer:

    Apparently, dieback is often seen on Cryptomeria, as the following information from North Carolina State University Cooperative Extension, no longer available online, suggests:

    Cryptomeria can have leaf blight or spot. Branch dieback is common. Dieback has not been associated with a disease but has been touted as the nature of the tree. Pathologists are still researching this. There may be some tip dieback associated with a disease.

    There is another discussion of a Cryptomeria with dead branches on University of British Columbia Botanical Garden's forum which mentions rust and needle blight (both fungal diseases) as possible causes.

    You may want to bring samples of the affected branches (along with your photo) to a Master Gardener Clinic for diagnosis.

    You may find this University of British Columbia Botanical Gardens Forum discussion of interest.

    The growth rate of a foot a year makes sense, considering that this is not a large tree. See below what Great Plant Picks, a Seattle-based website, has to say about this tree. An earlier version of the page linked here, from Iseli Nursery, indicates a growth rate of only 3-6 inches a year.

    Information from Iseli Nursery: Cryptomeria japonica 'Black Dragon' (Japanese cedar )
    Cryptomeria japonica is one of the most variable conifers you can imagine, with plants ranging from very dwarf rounded shrubs, trees with golden or contorted leaves, and wild forest trees to 80 feet high and 20 feet wide. 'Black Dragon' takes the middle road, neither too small nor too big. It has the deep green, needle-like leaves characteristic of this species and grows to about 7 feet high and 8 feet wide in twenty years. This very dark-foliaged conifer is easy to grow and combines well with plants having larger or variegated leaves.
    Japanese cedars thrive in full or part sun in well-drained, humus-rich, acidic soil and average moisture. May grow quickly when it first comes home from the nursery, due to the added fertilizer it gets there, but within a year it will settle into its dense, compact habit of growth.
    Cryptomeria japonica 'Black Dragon' is an evergreen, coniferous shrub. It grows wider than high, with an overall pyramidal shape. In 20 years it will reach only 7 feet high and about 8 feet wide.
    Hardiness: USDA zones 6 to 9

    Season All Season
    Date 2007-06-16
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    Keywords: liverworts, Mosses, Lichens

    PAL Question:

    Both my front and back gardens have become covered in moss and/or liverwort. It has intermingled with groundcovers such as sweet woodruff and blue star creeper. I have dug up the liverwort in the past but it comes back. Any suggestions towards eradicating it would be greatly appreciated.

    View Answer:

    It would be important to distinguish among mosses, lichens, and liverworts. Mosses and lichens are not harmful to garden plants. One species of liverwort is known to be a bit of a pest, mainly in greenhouse-grown plants. A first step would be to bring samples to a Master Gardener Clinic for identification. See the following on moss and lichen in gardens:

    There are researchers at Oregon State University who have done work on the species which is prevalent in greenhouses, Marchantia polymorpha, but the following information may not be relevant if that is not what you have growing in your garden. The first thing to do--if this is indeed the liverwort you are seeing--is to make sure you are not providing the ideal conditions for liverwort growth. Note that high nitrogen and phosphorus levels encourage growth: if you use fertilizer, check the levels of these nutrients. Avoid quick-release synthetic fertilizer. Below is information on methods of greenhouse (not garden) control of liverwort, from the OSU website:
    "Before talking about how to kill liverworts, let's talk about conditions in which liverworts thrive. Liverworts grow vigorously in conditions with high humidity, high nutrient levels (especially nitrogen and phosphorus), and high soil moisture. In an environment that has any of these 3 conditions, it will be difficult to control liverworts (even when using herbicides). In order to effectively control this weed, you must make growing conditions for the liverworts as difficult as possible. To do this, you should attempt to create an environment where the ambient air is dry, the surface of the container is dry (as dry as possible), and nutrients are not available on the container surface."

    The link above discusses postemergence control, but bear in mind that if something like acetic acid is used on liverwort growing on your plants it will affect the plants as well.

    The Royal Horticultural Society says that liverwort will not harm plants (except by causing competition for small plants) but its presence indicates compacted, acidic, and/or bare soil.

    The only time I have encountered liverwort is when transplanting nursery-purchased plants. With these, I physically remove the liverwort from the pot before planting into the garden. I wonder if your soil drains poorly, gets too much water, and/or too much fertilizer. I hope the information above will give you some ideas. Again, I recommend getting a conclusive identification before proceeding.

    Season All Season
    Date 2010-05-08
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    Keywords: Fungal diseases of plants, Mushrooms, House plants

    PAL Question:

    I have a potted plant with a fungus growing in the soil. It is bright neon yellow and grows like a mushroom, but with no cap on top. The plant is in the basement near a window. The soil is damp and I've avoided watering for awhile to let it dry out. What do you think the growth is, how to get rid of it, and will it be harmful to my plant? I keep plucking them, but they grow back.

    View Answer:

    I have had questions about the yellow houseplant mushroom before, and I am guessing you are seeing the same thing. It is called Leucoprinus birnbaumii.

    Michael Kuo's website, MushroomExpert.com has information about Leucoprinus. Excerpt:

    "This little yellow mushroom and its close relatives are the subject of many frantic e-mails to MushroomExpert.Com, since it has a tendency to pop up unexpectedly in people's flower pots--even indoors! The brightness of its yellowness exhibits some rebelliousness, but it often creates a striking contrast to the green houseplants that surround it.

    "Leucocoprinus birnbaumii won't hurt you, unless you eat it. It won't hurt your plant. It won't hurt your pets or your children, unless they eat it. There is no getting rid of it, short of replacing all the soil in your planter (and even then it might reappear). Since it makes such a beautiful addition to your household flora, I recommend learning to love it--and teaching your children to love it, too.

    "You might also impart the idea that mushrooms are very, very cool--but shouldn't be eaten. Perhaps your child would like to become an awesome and famous mycologist some day. I would love to encourage your child's interest in mushrooms by putting his or her drawing of Leucocoprinus birnbaumii on this Web page (at least temporarily).

    "Leucocoprinus birnbaumii is probably poisonous; do not eat it. Handling it, however, won't hurt you."

    Season All Season
    Date 2007-06-20
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    Keywords: Tulipa, Narcissus, Iris, Bulbs

    PAL Question:

    This is my first year planting spring flowering bulbs, which grew nicely. I cut the dead flower and the stalk once it died back, and now the foliage is yellow. What am I supposed to do with the yellow foliage? Pull it out? Cut it off? Just leave it alone? Also, will planting some annual petunias now hurt the bulbs I have planted in the garden? How close can I plant the petunia to the bulbs? I was going to try and hide the yellow foliage.

    View Answer:

    The answer will depend on which bulbs you were growing. For example, daffodil stems should not be cut back until at least 6 weeks after the flowers have faded, and you should never tie the foliage in knots or braid it (this is a common but ill-advised habit). You can leave daffodils in the ground to naturalize and spread.

    With tulips, you also need to wait at least 6 weeks from the fading of the flowers before cutting back the leaves.

    With hyacinths, you can pull away dead foliage and flower stems as they fade. When the top growth has died down, you can either leave them in the ground or dig up the bulbs, dry them off, and store them for replanting.

    If you are growing iris, you can cut the dead flower stems to the base, and cut away dead leaves in the summer. If they are bearded iris, the fan of leaves may be cut back in the fall to about 8 inches above the base.

    (Source: The Plant Care Manual by Stefan Buczacki, Crown Publishers, 1993)

    You can certainly plant your annual petunias quite close to bulbs like daffodils and tulips and other bulbous plants which are quite vertical. Just don't plant right on top of the bulbs. To disguise dying bulb foliage, use perennial ground cover plants that keep their leaves over the winter, and that have stems soft enough for bulbs to emerge through them. Hardy geraniums (true geraniums, also called cranesbill) and creeping veronica, such as Veronica peduncularis 'Georgia Blue,' are good choices. You can remove dried leaves as needed, and they can be tidied or groomed in early spring.

    Season All Season
    Date 2007-06-20
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    Keywords: Magnolia grandiflora, Winter protection of plants

    PAL Question:

    We are looking into growing evergreen Magnolias as part of our nursery stock. Do you know what varieties will be the most cold hardy in the Pacific Northwest, and will be able to handle heavy snow the best?

    View Answer:

    You may have already come across this garden forum discussion on this very topic on GardenWeb.

    Great Plant Picks suggests the variety 'Edith Bogue:'

    "The slow growth and controlled size of 'Edith Bogue' make it a good choice for courtyard and patio plantings, and its branches have strong resistance to breaking in wet winter snows."

    Their site also claims the variety 'Victoria' is resistant to damage from heavy snow.

    This article from the Arnold Arboretum mentions Magnolia virginiana 'Milton,' also evergreen and supposedly resistant to breakage from snow loads because of its smaller leaves:

    "The leaves are smaller in all dimensions than those of M. grandiflora, better suited to dealing with the snow loads that can be the death of the larger species, even for those cultivars that are otherwise quite hardy."

    I looked at several of our books on Magnolias, but snow load doesn't appear to be a consideration for the authors--perhaps they've never walked around the Pacific Northwest after a snowstorm, and seen all the sorry-looking evergreen Magnolias bent and broken in the parking strip gardens! I suspect that even the snow-load damage-resistant varieties are susceptible to a degree. I've been observing the ones in my neighborhood. Those with a more upright, narrow structure seem to fare just a little bit better (gravity may make some of the snow fall off the foliage?) than the really wide-branching ones.

    Season All Season
    Date 2012-02-04
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    Keywords: Fungal diseases of plants, Insect pests, Lonicera

    PAL Question:

    I noticed my honeysuckle, which is intertwined to look like a topiary bush with the greens and flower all bunched up at the top, to have yellowing of the leaves and drop off. Why are the leaves yellowing? It smells lovely and is green on the outside, but if you look under the canopy you can see many yellow leaves. Is it a disease? Should I use a fungicide?

    View Answer:

    There are a few possibilities. It might be a kind of leaf blight, as described by Iowa State University Extension.

    Leaf blight is a fungal problem, but the control methods described above are not nontoxic, so you may want to look for a safer fungicide (example here), and also try to prevent the ideal conditions for fungus. Avoid wetting the leaves of the plant, and make sure there is good air circulation around the plant (by siting it properly, and by pruning to keep the plant's shape open).

    Yellowed leaves could also be caused by scale, which is an insect. Do you see small bumps on the leaves and stems? If so, here are recommendations from The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale, 1996):

    "Minor infestations can be controlled by scraping the insects off the plant with your fingernail, and by pruning out the most infested parts of the plant. You can also use a soft brush and soapy water to scrub scales off the stems, or you can apply dormant oil to the trunk and stems of the plant just before growth begins next spring, and use superior oil during the growing season."

    Because I'm not certain which type of problem your honeysuckle may have, you should bring a sample to a Master Gardener Clinic.

    Season All Season
    Date 2008-02-07
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    Keywords: Dendrobium, Orchidaceae (Orchid family)

    PAL Question:

    I just got a Dendrobium, it is Dendrobium eima x impact. The flowers are pink and white. I was wondering how I can tell if it is a deciduous one or an evergreen one. I still have months before winter, but want to make sure I give it the rest it needs when the winter does get here.

    View Answer:

    There are deciduous and evergreen types of Dendrobium. Unfortunately, I could not find information about the variety you are growing. If yours has soft canes, it is deciduous; hard canes are characteristic of the evergreen type. Here is information from Orchids Made Easy:
    "Dendrobiums are separated into two main groups: hard-caned and soft-caned. Hard-caned Dendrobiums have tall pseudobulbs that are very thin and their leaves are generally a little darker in color than the soft-caned. Hard-caned Dens are evergreen and often keep their leaves for many years before they drop them. Hard-caned Dens grow spikes from the top of the cane and produce gorgeous flower sprays.

    "Soft-caned Dendrobiums have leafy pseudobulbs that are long and slim. Their leaves are generally a little lighter in color than the hard-caned Dens. They grow leaves along the length of the cane and the blooms sprout from the individual stems that are along the cane itself. Soft-caned dendrobiums are deciduous and drop their leaves when the weather gets cold."

    The American Orchid Society has a guide to growing evergreen Dendrobium for beginners.

    There is also good general information on caring for orchids in the Brooklyn Botanic Garden guides on the subject. Generally, winter is the time to hold back on watering a bit, but also be careful about the plant's need for humidity--our heated homes in winter can be exceedingly dry. According to Orchids by Joyce Stewart (Timber Press, 2000), most orchids prefer 65-75% humidity during the day. She recommends "damping down last thing at night" during the winter (using a spray bottle or mister), if you have heat on in your house overnight.

    Season All Season
    Date 2007-06-20
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    Keywords: Beans--Diseases and pests

    PAL Question:

    I have planted green beans three times because I have an annual problem of the leaves either being completely chopped off or they appear lacy and nearly gone. I have seen slug slime, so that may be some of the problem, but what does the lacy leaf indicate? I also have a lot of "potato bugs" or "sow bugs," could that be the problem?

    View Answer:

    According to The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale, 1996), lacy leaves on your bean plants might be the work of Mexican bean beetles. Parasitic wasps (Pediobius foveolatus) can be used to control the Mexican bean beetle. As a last resort, you can spray or dust your plants with pyrethrin. See links here:

    From the Connecticut Agricultural Experiment Station

    From the University of California

    Large holes in the leaves may be caused by other beetles as well, such as the cucumber beetle, which can be managed by protecting your plants with row cover like Reemay. If damage is severe, you can use pyrethrin or neem spray.

    Small holes in the leaves may be the work of flea beetles, and the management is the same as above.

    The chopping off at ground level sounds like it could be the slugs eating shoots as they emerge, or climbing up the plant and eating it down to the ground. It could also be the result of cutworms. Look for these at dusk, and look during the day at or just below the soil surface. I manage these pests by looking for them frequently, and squishing them or cutting them in half with my pruning shears.

    I had never heard of sow or pill or potato bugs (isopods) being a vegetable pest, but apparently they do have that potential if the population is large enough. See the discussion among gardeners on Gardenweb.

    You might try fooling the pests by planting your beans in a different location, especially a raised bed.

    Season All Season
    Date 2007-06-20
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    Keywords: Trees--Wounds and injuries, Thuja plicata

    PAL Question:

    I have a mature Western red cedar with an inverted-V gap in the bark, right at ground level. The point of the V is about 2 ft. off the ground; the base of the gap is perhaps 9-10" across. What's the current thinking on protecting this exposed area from diseases and critters? Paint with some sort of goop? Leave it alone? Or something else?

    View Answer:

    Here is a link to information on managing bark injuries, from Cornell University's Plant Disease Diagnostic Clinic, which includes illustrations. Excerpt:

    "When a split occurs on a tree, what should you do? In recent years, quite a bit of research has been done on closure of tree wounds. These investigations have indicated that tree wound paints are of little value in helping a tree to callus over. For this reason, do not paint or try to seal a split with paint or tar. Tracing the bark around the split can be very helpful in aiding wound healing (Fig. 2). With a sharp knife, starting from one end of the split, trace around one side of the wound, about 1/2 to 1 inch back from the split bark. Stop at the other end and do the same procedure on the opposite side of the split. Knives should be sterilized between cuts by dipping them for several minutes in a 1:10 bleach:water solution or a 70% alcohol solution to avoid contaminating the cuts. Carefully remove the bark from inside the traced area. You should now have a bare area resembling the diagram in Fig. 2. Remember to leave this untreated. A tree growing with good vigor usually calluses over quickest. Encourage vigor in the tree with yearly spring fertilizer applications -- and be sure to provide adequate irrigation in hot, dry weather. Bark splits will often close over completely leaving a slight ridge in the trunk where callus tissue has been produced."

    The book Practical Tree Management: An Arborist's Handbook by T. Lawrence et al. (Inkata Press, 1993) confirms the method described above. Trim back the bark to healthy tissue around the wound using tools such as a chisel, gouge, hammer, and sharp knife. Wound margins should be rounded, and damaged wood within the wound should be smoothed with a chisel or gouge, but only to the most minimal level (don't go deep).

    If in doubt, I would recommend contacting a certified arborist for assistance. You can obtain a referral from Plant Amnesty or the Pacific Northwest chapter of the International Society of Arboriculture.

    Season All Season
    Date 2007-06-22
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    Keywords: Micropropagation, Acer palmatum

    PAL Question:

    Do you have any information about micropropagation of the Japanese maple?

    View Answer:

    I found a series of replies to a question like yours on the University of British Columbia Botanical Garden's online forum.

    An article formerly available online from the Oregon Association of Nurseries states the following:

    "Keeping up with the demand for 'newness' means learning about and trialing different propagation techniques. That's where tissue culture, or 'in vitro micropropagation,' has been used as one propagation tool of many in the tool chest, said Gayle Suttle of Microplant Nurseries Inc. in Gervais, Ore. The company focuses on shade trees and shrubs. "No technique will dominate," Suttle said. 'What's going to work for the industry is, number one, focusing on quality and, number two, efficiency. If you sacrifice quality for cost, then you lose.'

    "Micropropagation helps many nurseries get a jump-start on production of new items, improve the reliability of plant performance and start with clean stock. In the area of woody plants, micropropagation has had a particular impact on the nursery industry, allowing growers to cut the time needed to establish mother blocks and meet production demand, Suttle said. Also, there are some plants where branching is hard to come by, and micropropagated plants tend to branch more. 'If you can grow a plant by seed, there's nothing that beats throwing a seed into the ground,' she said.

    "But there are plants for which normal propagation has problems -- the seed source is unreliable or unavailable, a graft is incompatible with its scion, budding problems arise in the field or roots fail to form on cuttings. Micropropagation fits as one way to keep growers successful and efficient.

    "'Twenty-five years ago, there was a fear that micropropagation was going to take over the world,' Suttle said. 'That's never been a concept that's panned out. The industry is such a variable industry, with different people doing things differently. The goal is to be successful. You can save all kinds of money, but if you have a rotten plant, no one's going to buy it. Customers may buy a cheap plant one year, but if the quality is not behind it, they won't be back next year. They'll be looking for something else.'

    "It was plant health and survivability that drove Dieringer Nursery Company toward organic growing practices nearly 13 years ago, and those goals keep the nursery from fully jumping into use of tissue culture. The company grows rhododendrons, relying mostly on vegetative propagation with a small smattering of grafting and an even smaller sample of plants produced via micropropagation.

    "'Every couple of years we will bring in some tissue culture to evaluate the plant under our growing procedures, we'll get a new variety and it comes in by tissue culture,' said Jeff Dieringer, president of the Hubbard, Ore.-based company.

    "The advantages of propagation by cuttings over other methods are exact replication of desired genetic characteristics and the more rapid time frame to finished product compared with starting from seed. Nearly all of the hundreds of thousands of rhododendrons Dieringer nursery handles in a year are grown using vegetative propagation, while maybe only a couple hundred are started from in vitro micropropagation.

    "'It's a way to introduce a plant, but we don't get tissue culture starts and turn them into production plants,' Dieringer said. 'We watch that plant, its habits under our growing condition for three to four years to see if it exhibits normal growth. We do vegetative cuttings then, if they don't exhibit any juveniles.'"

    The Miller Library has several titles on micropropagation in general, but I did not find anything specifically addressing use of this method with Acer palmatum. A good general text with several chapters on in vitro culture is A Color Atlas of Plant Propagation and Conservation by Bryan G. Bowes (New York Botanical Garden Press, 1999).

    Season All Season
    Date 2007-06-23
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    Keywords: Bergenia

    PAL Question:

    I am trying to find out the difference between Bergenia Winterglut, elephant ears, and Bergemia pig squeak. The landscape plan I am following calls for the pig squeak, but I could only find elephant ears. Is Winterglut something special?

    View Answer:

    I think that the confusion arises from the fact that 'pig squeak' is a common name for Bergenia, as is 'elephant ears,' while 'Winterglut' is part of a cultivar name (Bergenia cordifolia 'Winterglut'). Bergemia with an "m" in the middle is just a typographical error. 'Winterglut' is also known as 'Winter Glow.' See the excerpt from Greer Gardens Nursery catalog below:

    BERGENIA - PIG SQUEAK - (-40 F, USDA Zones 3-8) Bergenia are tolerant of a wide variety of conditions but soil that is too rich can cause soft foliage. Providing the plant with poorer soil conditions and some exposure, you will enhance the winter color. This plant prefers some shade, but will thrive in full sun if soil is deep and moist enough. Not for south Florida or the Gulf Coast.

    30047 'Bressingham Ruby' - The mound of rounded, deep green leaves are up to 8" long. The foliage is maroon on the underside, and will turn beet red in the winter. In the spring, flowers of a very intense red are borne on nodding cymes. Will get 1' tall.

    30965 'Bressingham White' - Has large, dark green foliage which is adorned by blooms that start out light pink and then fade to a pure white. They reach 12-15'' in height and blooms appear in the spring.

    31673 ciliata - (-20 F, USDA Zones 5-8) Large (12'') fuzzy, rounded leaves and white flowers in early spring make this deciduous Chinese species a standout. Part shade and moisture retentive soil. Low growing to 10''.

    cordifolia - (-30 F, USDA Zones 4-8)

    31562 'Eroica' - Dark purple flowers in early spring. Foliage changes from light green to deep copper in fall, then a brownish red after first frost.

    31035 'Winter Glow' - Deep reddish pink flowers bloom in spring, held above evergreen leaves. In the winter the leaves turn deep red. Will be 1' in height.

    From Thimble Farms in British Columbia:

    Bergenia `Winterglut' Ht.45cm. Z2. Thick clusters of florescent red flowers and dark green foliage . Fantastic red fall highlights

    You may find this information from the website of a Seattle area gardener, Paghat's Garden, and this additional page, of interest. Excerpt:

    "A good plant nearly impossible to kill is Bergenia, named for the 18th Century German botanist Karl August von Bergen. It is called Elephant Ears because it has giant round or heart-shaped leaves. My grandparents called Bergenias the Elephant Plant, because if an elephant stomped on it, it wouldn't die. But I notice the Sunset Guide only calls it by its scientific name, giving it no common name at all, so Elephant Ears may be somewhat a regional name, & Elephant Plant just the name our family used without authority.

    "We get good red winter colors on our B. cordifolia 'Winterglut' & B. cordifolia 'Abendglocken.' The first photo at the top of this page shows both of these when they were first stuck into the hillside as tiny starts. In that early-April 2002 photo, the 'Abendglocken' on the left has already turned from red back to green & is starting to bloom, showing a glint of color in its buds. But 'Winterglut' on the right still shows a chocolaty-colored leaf, which began to green shortly after photographed."

    Season All Season
    Date 2007-07-02
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    Keywords: Plant diseases, Holly

    PAL Question:

    I purchased a gallon size Japanese Holly (Ilex crenata 'Sky Sentry') 5 years ago and put it in a 12" diameter container. It has not grown much, and has been looking bad lately, so I thought it was probably root bound. To my surprise, when I took it out, there were no new roots--the root ball was about 3" deep and 6" across. Is this a normal root for the Ilex? What does it need to thrive?

    View Answer:

    Since you mention that the plant is not looking healthy, I wonder if it may have root rot.

    According to North Carolina Cooperative Extension, Ilex crenata is highly susceptible to this fungal problem.

    It is possible that there are nematodes feeding on the roots and diminishing the plant's ability to get water and nutrients from the soil.

    Another North Carolina Cooperative Extension site provides descriptions of several problems affecting hollies.

    The Organic Gardener's Handbook of Natural Insect & Disease Control by Barbara Ellis (Rodale, 1996) says that Ilex roots grow close to the surface, so perhaps the size of the root ball is not abnormal.

    Missouri Botanical Garden has general information on this plant.

    To determine what exactly is causing the plant's ill health, you may want to bring pictures and samples of the affected parts of the Ilex to a Master Gardener Clinic.

    Season All Season
    Date 2007-06-27
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    Keywords: Nicotiana, Poisonous plants

    PAL Question:

    Can I grow flowering tobacco varieties, such as Nicotiana sylvestris, and harvest the leaves for smoking?

    View Answer:

    Nicotiana species are in the Family Solanaceae. Nicotiana sylvestris is a parent of cultivated tobacco, N. tabacum. You can surmise that the cultivated tobacco plant was bred for characteristics that the ornamental plants were not—that is, use of the leaves for smoking without (immediate, anyway!) dire toxic consequences. All Nicotiana species have toxic properties, but levels of those substances may vary from species to species, so it would be unwise to assume that leaves from the other varieties are 'safe' to smoke. For example Nicotiana glauca, a weedy species also called tree tobacco, does not contain nicotine but instead anabasine, which is extremely toxic to humans and animals, according to this weed report from Weed Control in Natural Areas in the Western United States.

    According to The North American Guide to Common Poisonous Plants and Mushrooms (Nancy J. Turner and Patrick von Aderkas, Timber Press 2009), "all tobaccos should be considered poisonous to consume (smoking brings its own risks); some have caused fatalities. […] Poisoning through intentional or accidental misuse of nicotine and products containing it is a relatively common occurrence. Related species may contain other toxic alkaloids, chemically similar to nicotine." For this reason, we suggest that you enjoy Nicotiana sylvestris, N. alata, and other ornamental species for their flowers only. Also avoid growing Nicotiana near plants like tomatoes and others in the Solanaceae which are susceptible to tobacco mosaic virus (in fact, don't touch those plants after handling Nicotiana, or smoking tobacco products).

    Season All Season
    Date 2016-02-27
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    Keywords: Bacterial diseases of plants, Syringa

    PAL Question:

    I have a 'Palibin' lilac that appears to have a bit of bacterial blight. I have pruned out the diseased branches. Is it too late to spray to control the disease? I didn't do a dormant spray this year, and haven't done any preventive spraying to this point, either. If it isn't too late, what spray product would you recommend? What else can I do to keep the blight under control?

    View Answer:

    There are cultural methods of dealing with bacterial blight you should try before using any spray. The information below should help.

    Washington State University Extension's HortSense website recommends:

    • Avoid injuring plants to reduce possibility of infection.
    • Avoid overhead irrigation.
    • Maintain proper plant nutrition. Healthy plants resist disease better.
    • Plant disease-resistant species such as Syringa perkinensis, S. microphylla, or S. vulgaris vars. 'Alphonse Lavallec', 'Crepuscule', 'Floreal', 'Guinevere', 'Jeanne d'Art', 'Lutece', 'Maud Notcutt', 'Mrs. W.W. Marshall', 'Rutilant', or 'William Robinson'.
    • Prune and destroy infected tissues as soon as they are noticed.
    • Space plants properly and prune to provide good air circulation. This will slow down spread of the disease.

    Here is more information from University of California, Davis's Integrated Pest Management site. Excerpt:

    "Bacterial blight is promoted by prolonged rainy springs. Symptoms may be more extensive in wetter areas. Prune branches showing dieback and severe blight. Space plants to provide good air circulation. Prune during the dry season when infection is less likely to occur. Do not wet foliage with overhead irrigation; do not overfertilize. Small plants can be protected to some degree by keeping them covered by plastic (or moved under plastic). Plant resistant species if available. If the disease is systemic or cankers appear on the trunk, the tree will probably die and should be removed. If the disease is confined to leaves, damage is not usually serious and trees normally recover. Sprays do not give reliable control."

    Season Spring
    Date 2007-06-27
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    Keywords: Anemone

    PAL Question:

    Do you have any suggestions for controlling the spread of some too happy Japanese Anemones? I know they spread by underground roots but do they also spread via seeds? If I put down a barrier how deep should it go?

    View Answer:

    I have also experienced this in my garden, and it is not difficult to dig up Japanese anemones and either compost them or offer them to fellow gardeners (with a warning!). Anemone x hybrida spreads easily by roots but can be propagated from seed. It is most likely that the spreading of the plant in your garden is mainly rhizomatous (by roots). If you don't want to dig up the occasional clump, you could try getting rid of the plant in areas where you do not want it, and then putting barriers such as plastic edging around the clumps you want to keep, although I think this requires at least as much labor as removing any unwanted anemones. Also, cut off spent flower stalks if you want to avoid seeds. However, the seedheads are flossy and ornamental in winter.

    Here is general information on this plant, from Cornell University.

    Here is information from University of Minnesota Sustainable Urban Landscape Information Series about edging material (use the search box in the upper right corner and search for 'edging'). This may give you some ideas on ways of containing the spread of the roots.

    Season All Season
    Date 2007-06-28
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    Keywords: Fragaria, Cutworms, Fruit--Diseases and pests

    PAL Question:

    My small patch of strawberry plants has this year suffered from green fruit dropping off, forming neat piles under each plant. Each fallen fruit has a short bit of stem still attached. A few fruit are still attached. No sign of slug or squirrel damage, no signs of fungus of insect attack. The weather has been colder and wetter than average. Owing to natural layering, the plants are closer together than when first planted. This happened a couple of years ago, but we had a good crop last year. Any idea what's going wrong?

    View Answer:

    I wonder if this might be the work of cutworms. You can take a close look just under the soil surface, along the stems, and inside curled or folded leaves during the day, or take a flashlight at night, which is when they feed, and see if that may be why your strawberries are being cut away from the plant. If you find them, cut them with garden pruners.

    Washington State University's pest and disease site does list the cutworm as a known pest of strawberries. Excerpt:

    "Cutworms and armyworms are the larvae of noctuid moths. These common moths are medium-sized with fairly dull coloration. The greenish, grayish, or tan caterpillars are hairless, nocturnal, and generally spotted, striped, or otherwise marked. They may be 1/4" to 1" in length and tend to curl up when disturbed. They may climb into the plant and feed on foliage, buds, flowers, or fruit. Armyworm behavior is similar to that of cutworms, but armyworms feed in large groups instead of individually. They tend to be voracious feeders. The caterpillars typically spend the day just beneath the soil surface or under debris near the host. Weeds are a primary food source for both cutworms and armyworms."

    I looked at Pests of the Garden and Small Farm by Mary Louise Flint (University of California, 1990), but could not find any strawberry disease resembling what you have observed in your garden, which leads me to believe it is a pest problem. Here is a link to U.C. Davis's Integrated Pest Management page on strawberries.

    Season All Season
    Date 2007-06-28
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    Keywords: Hedera helix, Invasive plants--Control

    PAL Question:

    In trying to eradicate English Ivy I am considering using Clorox on the roots. I have cut off all of the leaves. Is this safe and do I need to guard against nearby roots from trees that I want to save? If the Clorox will work I am assuming that I would use it undiluted for maximum effect. Any other ideas on English Ivy eradication?

    View Answer:

    Ivy is a tough plant to eradicate, as I imagine you already know. The resources I have consulted indicate that manual removal methods are more effective than chemical methods. Ivy apparently has an excellent defense system against chemicals. I could find nothing in the literature that suggested using bleach to kill the roots of Hedera helix (English ivy).

    Here are links which may be of use to you.

    From King County Noxious Weed Control.

    From Portland, Oregon's No Ivy League.

    Local garden writer Ann Lovejoy's article in the Seattle Post-Intelligencer. Excerpt:

    "Why not just poison it? Using herbicide on ivy is both futile and dangerous. Ivy's waxy foliage repels herbicides, which run off to damage nearby plants and pollute water systems.

    "To safely and steadily get rid of ivy, begin by cutting all vines that have scrambled up trees or posts. Remove as much as you can reach from each trunk. If you miss a few stubborn scraps here and there, don't worry about it. Just be sure that none of the vines remain uncut or are left dangling.

    "Now remove all ivy at ground level by pulling strands and prying roots with a small hand-mattock or hori-hori (Japanese farmers' knife). Even if you miss a few roots (as you will), they won't all sprout back.

    "Finally, mulch with a combination of woodchips and compost if you plan to replant soon. If you just want to keep the ground clear for a while, use coarse wood chips for mulch.

    "To keep the mulched area clear, check it two or three times a year. You can quickly remove any new shoots that appear, along with as much root as possible."

    Season All Season
    Date 2007-06-29
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    Keywords: Frost

    PAL Question:

    This winter, I was walking past a neighbor's garden and noticed a few dried stalks (not sure what the plant was) that were sprouting a candy floss-like substance. When I got down close, I could see it was ice coming out of cracks in the stems. What causes this phenomenon? Does it happen to only certain types of plants?

    View Answer:

    You were fortunate enough to witness an example of frost flowers, also called ice flowers, or crystallofolia, a term coined by Bob Harms (University of Texas, Austin) to distinguish the phenomenon from "frost flowers" which are sea ice. Not all plants exhibit these fanciful formations of ice crystals, but sometimes their common names will hint at this potential. Verbesina virginica, native to most of the central and southern reaches of the eastern United States, is known by the names frostweed and white crownbeard; Helianthemum canadense is sometimes called rock frost or frostwort. This is not a widespread occurrence, and there is no clear pattern dictating which plant families or genera are likely to produce these ribbon-like excrescences. A few others which do this include American dittany (Cunila origanoides), Isodon excisa and I. rubescens.

    In a column (from December 18, 2013) called The Buzz, Memphis Botanic Garden's website explains the formation of flowers as follows: "When the ground is warm enough for the plants' roots to still be active, but the air temperature drops below freezing […] juices from the plant are expelled through slits in the stems […] This may happen multiple times over the winter since our ground rarely freezes far down, but once the moisture is gone, so are the frost flowers." The theories and explanations of why certain plants do this are far more complex. It may have to do with the xylem rays which carry sap from the center to the periphery of the stems, according to James R. Carter of Illinois State University. Plants with prominent rays are more likely to have ice flowers, which may be using the xylem rays as a source of fluid.

    If you would like to increase the odds of witnessing these fascinating ice formations again in your own garden, you could try growing some of the plants on Carter’s list (avoiding any which are invasive in our area!).

    • Anemone halleri
    • Ceratostigma willmottianum
    • Echinacea species
    • Eupatorium cannabinum
    • Helleborus argutifolius
    • Origanum vulgare
    • Plumbago auriculata
    • Salvia coccinea

    To this list, I would add Monarda didyma, the only plant on which I have ever seen frost flowers in Seattle.

    Should you wish to read more, and see additional illustrations, there is an article by James R. Carter entitled "Flowers and Ribbons of Ice" in American Scientist (September/October 2013 ). The website Kuriositas also has a page of photographs of "Frost Flowers: Nature's Exquisite Ice Extrusion."

    Season Winter
    Date 2015-09-01
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    Keywords: Dracunculus

    PAL Question:

    I recently purchased a house that has a relative of the corpse plant in the yard. It is a perennial about 30" tall and has been in bloom since yesterday with a deep burgundy bloom that is about 10" long. It has delicate, deeply lobed leaves.

    Any idea what it could be or how to care for it? I was considering transplanting it since it sits just below our dining room window, under the eave of the house. Stinky! I imagine it will only bloom for a short time. Could it be rare?

    View Answer:

    I am guessing that what you have is the voodoo lily, or Dracunculus vulgaris.

    The website of a Pacific Northwest gardener, Paghat, has information about this plant with pictures for you to compare with the plant in your garden. Vanderbilt University also has images of this plant on its Bioimages page.

    For contrast, here are images of corpse flower, Amorphophallus titanum.

    According to The Royal Horticultural Society's A to Z Encyclopedia of Garden Plants edited by Christopher Brickell (DK Publishing, 1996) the plant you have is frost-hardy, and grows best in full sun but will tolerate partial shade. You can protect it with a winter mulch. Native to the Mediterranean, Madeira, and the Canary Islands, they grow well in open glades in sheltered woodland, or at the base of a sunny wall. From what I have heard from other gardeners (we receive several questions a year about this plant), they do spread over time. If you wish to increase their numbers, they can be propagated by separating offsets in fall or spring.

    Season All Season
    Date 2007-06-15
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    Keywords: Lilium (Lily family), Bulbs

    PAL Question:

    How do you remove the dead flowers from a Asiatic lily? Do you go to the main stem and cut it there or do you just remove the flower and leave the pod?

    View Answer:

    Here is what University of Minnesota Extension advises:

    "Deadhead flowers as they fade, by breaking them off carefully. That way, none of the plant's energy is 'wasted' on seed production. Do not remove stems or foliage, though. They'll continue to put energy into the bulb as long as they remain green. Remove old foliage in late fall or early spring by cutting down the dead stalks."

    Season All Season
    Date 2007-06-25
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    Keywords: Propagation, Cyclamen

    PAL Question:

    I have a Cyclamen that blooms in the fall, so I think it would be C. hederifolium. Right now there is a clump of 1/2 in. diameter "seeds" attached to curly spirals. I'm wondering if I can harvest those seeds and give them to others. In the book I'm reading, they say it is propagated by corms, which I assume I would find if I dug them up. What should be done at "cleanup time," which seems to be about now, as there are only a few dried up leaves left, and all those "curls and pods." I've had it several years and have done nothing to it. It blooms beautifully in the fall each year with deep pink flowers. I do see tiny starts at various places in the yard, so some seeds have moved around.

    View Answer:

    Propagation by seed is the most commonly recommended method according to the following resources:
    American Horticultural Society Plant Propagation: The Fully Illustrated Plant by Plant Manual of Practical Techniques by Alan Toogood, The Royal Horticultural Society A-Z Encyclopedia of Garden Plants by Christopher Brickell, The Complete Book of Plant Propagation by Jim Arbury, Richard Bird, Mike Honour, Clive Innes and Mike Salmon, The Plant Care Manual by Stefan Buczacki and Cyclamen; A Guide for Gardeners, Horticulturists and Botanists by Christopher Grey-Wilson. Apparently propagation from corms is technical and difficult. However, if you choose to give it a try, The title Cyclamen, mentioned above, does go into some detail about the process.

    You can thank the ants for the tiny starts you are finding in your yard, they eat the "sweet and sticky mucilage" that covers the seed, they then leave the seed alone where it lies, ready to germinate on its own afterward. (Cyclamen) As for the clump of seeds you are finding on your plant, their dark brown color indicates they are ripe and ready for sowing. They require dark, cool temperatures for germination (43-54 F) for C. hederifolium. It is recommended that the seeds soak for a minimum of 10 hours (a small amount of gentle detergent can be added) and rinsed thoroughly. They can be sown at the end of summer and produce flowers in about 14 months. (The Royal Horticultural Society A-Z Encyclopedia of Garden Plants and American Horticultural Society Plant Propagation).

    Unfortunately I couldn't find much information for your question regarding clean up. However, I would suggest that it would be perfectly acceptable to remove the dead leaves and seed pods, including the curly spirals that are attached to them. You can choose to sow the seeds or give them away to friends. As long as you don't disturb the exposed curled tubers that may be present at or near the surface of the soil, I think you'll plant will be fine. You may also want to consider adding additional plants that show their true colors in the summer when your Cyclamen is dormant. This would mask the appearance of your Cyclamen and perhaps dissolve any need for clean up.

    Season All Season
    Date 2007-07-05
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    Keywords: Pests, Amaryllis

    PAL Question:

    My Amaryllis bulbs are infected with syrphid flies. I have dug them but don't know what to do with the bulbs. What can I do to save them?

    View Answer:

    Until receiving your question, I had always known of syrphid flies as beneficial insects in the garden, so I considered the possibility that the bulbs might be infested with bulb mites, or mealybugs, which are fairly common pests of Amaryllis. That being said, in my research to answer your question, I came across an article by Whatcom County Washington State University Extension agent Todd Murray which describes the Narcissus bulb fly, which is indeed a syrphid fly, and does sometimes infest Amaryllis bulbs. Excerpt:

    Monitoring and Management: There are no pesticide recommendations available for these bulb flies. But that's O.K.; we have many alternatives that we can use to avoid mushy bulbs. You should be thinking about trying these practices if you have a problem with bulb flies.

    • In May, on sunny days look for large bumblebee-like flies hovering around your flowers. Bumblebees will have two pairs of wings while bulb flies will have one. Grab your handy insect net (you all have one, right???) and catch the critters before they can do too much egg laying. This sounds tedious, but is very effective for protecting small plantings of susceptible bulbs. Remember, each female fly can lay up to 100 eggs! Plus, if it is a nice sunny day, you should be outside admiring and tending your garden anyway.
    • Adult flies use visual cues and smell to locate your delicious bulbs. After you have enjoyed your flowers, cover the bulb bed with a floating row cover, like Reemay*. Another recommendation given suggests that you mow down the vegetative portions of your plant and gently cover the tops with soil. Female flies will be unable to locate the bulb. Once no new foliage is sprouting, remove and store the bulb through the off-season. If you do this, I do not know the impacts this will have on next year's flower. That vegetation produces the bulb's energy reserve that is needed for next year's growth. Regardless, the earlier you can pull your bulbs out, the better chance that you will avoid bulb flies.
    • Bulb flies are less active in open, windy areas. Plant your beds in exposed windy places, if your landscape provides this type of climate.
    • Avoid any damage to the bulbs when handling and planting. The lesser bulb fly prefers damaged goods to healthy bulbs. Establishment of maggots is much easier if there are already rot producing organisms in the bulb.
    • Plant your bulbs deep, if they can tolerate it. Bulbs planted 25cm (or about 10") deep in the soil will evade attack by adult flies. I am unaware if planting this deep is practical.
    • When the time comes to pull up the bulbs, check the basal plate of each bulb. When you purchase new bulbs, check the plate for any signs of squishiness and rot. If you find some rot there, do not plant them and discard the rotten bulbs.
    • Infested or suspicious bulbs can be cleaned of maggots by soaking bulbs in hot water (43-44 C) for at least 40 minutes. Care must be taken to not exceed this temperature, because you will damage the bulb. This is a great way to kill other pests of bulbs, too.
    • Finally, if the problem persists, the sure-fire way to avoid bulb flies is to buy your flowers at the store like all the non-gardeners and black-thumbers out there. If you don't plant it, they won't come. This option is the one that I'm going to take now.

    In the event that there are other pests present on your bulbs, this information from University of Florida Extension may be of interest. Excerpt:

    "Spider mites are tiny animals (1/50 inch or 0.5 mm long) that cause injury similar to that of sucking insects as they feed on the leaves of amaryllis during warm, dry periods. Bulb mites attack rotting bulbs and tunnel into healthy bulbs, transmitting organisms that produce bulb rot. Bulb mites are particularly damaging to bulbs of amaryllis. Mealybugs are soft-bodied insects covered with a white, waxy material. When mature, they vary from 1/50 to 1/3 inch (0.5 to 8.5 mm) in length. They damage plant foliage by sucking plant fluids and may invade stored bulbs. Some control can be obtained by frequent syringing with a hose."

    In case you are curious, here is information on the beneficial properties of syrphid flies, from University of California, Davis Integrated Pest Management.

    Season All Season
    Date 2007-07-06
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    Keywords: Salvia, Drought-tolerant plants

    PAL Question:

    I recently planted several purple Salvia plants that have completely faded from beautiful, bright purple to beige. It has been really hot and dry and I've been watering them in clay soil once to twice a day. Is it possible that I'm overwatering them? Or do they need even more water since they were just planted?

    View Answer:

    I'm not sure what type of Salvia you are growing, but it is possible you are overwatering them. The heavy clay soil combined with watering 1-2 times daily sounds like too much for a plant that is drought-tolerant once established. To learn more about growing ornamental salvias, see this University of California, Davis Arboretum Review, #44, Fall 2003 article, "Salvias for Every Garden" by Ellen Zagory.

    I would suggest watering less often, but watering more deeply, and possibly mulching around the plants. Some xeriscaping resources suggest using gravel, and it is mentioned in this document from New Mexico State University Extension, "Landscape Water Conservation: Principles of Xeriscape" by Curtis Smith, with the caution that although "some plants native to very well drained soils grow better in gravel mulches [...] rock mulch becomes very hot in our climate and can injure or limit growth of some plants. Ultimately, the mulch should be shaded by landscape plants that will provide environmental cooling. Using gravel mulch alone as a landscape element may result in increased home cooling bills and require greater weed control efforts."

    This article by Seattle-area garden writer Ann Lovejoy on drought-tolerant gardening may also be of interest.

    Season All Season
    Date 2007-07-09
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    Keywords: Hedera, Invasive plants, Climbing plants

    PAL Question:

    My question is about ivy for growing up a brick wall. What would you recommend? How do Boston ivy and English ivy compare for this purpose? We live in New Jersey.

    View Answer:

    First of all, it is important to know that clinging plants, such as Boston ivy and English ivy have the potential to "damage old, soft mortar and strip off pebbledash". (Gardening with Climbers by Christopher Grey-Wilson and Victoria Matthews) It is also suggested that these vines have a "structurally sound surface and must be prevented from reaching under house eaves and roof tiles and into window casements." (The New Royal Horticultural Society Dictionary Manual of Climbers and Wall Plants edited by JK Burras and Mark Griffiths)

    The New Jersey Invasive Species Strike Team has a factsheet on both English ivy (Hedera helix)and Boston ivy (Parthenocissus).

    In addition to taking this information into consideration, it would also be important to identify the amount of sunlight and the extent to which the side of the house will be exposed to harsh winter winds and temperatures. Neither Boston nor English ivy is recommended for full sunlight. Boston ivy will give you more fall color and interest and will withstand cold winters. (Simon & Schuster's Guide to Climbing Plants by Enrico Banfi and Francesca Consolino)

    If you want to consider an alternative vining plant, you might want to install a trellis. That way you will not have to rely solely on vines which cling to the brick. You could try Clematis or some the honeysuckle species that are native to the northeastern U.S. There are several listed in this article by William Cullina, "Alternatives to invasive or potentially invasive exotic species," from the New England Wildflower Society:

    • Lonicera ciliosa (Orange Honeysuckle)
    • Lonicera dioica (Limber Honeysuckle)
    • Lonicera flava (Yellow Honeysuckle)
    • Lonicera sempervirens (Trumpet Honeysuckle)

    Season All Season
    Date 2007-07-02
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    Keywords: Ensete

    PAL Question:

    I have a small, red-leaved banana plant. I am going to give it to my daughter in Iowa. What is the best care she can give besides full sun and moisture? What kind of dirt is best for replanting it and what kind of fertilizer should I feed it?

    View Answer:

    You are correct that Ensete ventricosum (Red banana) needs moisture and sun to thrive. The information I found about this plant indicates that it is not too particular about type of soil, but it is definitely frost-tender. Does your daughter plan to overwinter the banana in a greenhouse or other sheltered spot? The Missouri Botanical Garden site linked below suggests applying fertilizer during the growing season, but does not mention a particular type of fertilizer. (See last link below for more anecdotal information on fertilizer.)

    Missouri Botanical Garden has useful information on growing Ensete. Below is an excerpt.

    Winter hardy to USDA Zones 10-11. In St. Louis, plants may be grown outdoors during the growing season (either directly in the ground or in containers), but must be brought indoors for overwintering or they will not survive. Plants are best grown in organically rich, medium moisture, well-drained soil in full sun. Plants tolerate and often appreciate some part shade or light filtered sun in the heat of the day. Plants need consistently moist soils that do not dry out. Fertilize plants regularly during growing season. Site plants in areas protected from strong winds which can severely damage the large leaves. For containers, use a well-drained potting soil mix. Keep container soils consistently moist but not wet. In St. Louis, outdoor plants must be overwintered indoors, either in a sunroom/greenhouse or by forcing plants into dormancy. Options for overwintering include:

    1. Bring container plant indoors in fall before first frost and place container in a large sunny room for overwintering as a houseplant, with reduced water and fertilization;