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PAL Questions: 828 - Garden Tools: 345 - Recommended Websites: 680

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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 Grapes in Your Home Garden of interest as well.

Season All Season
Date 2008-01-24
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Keywords: Hummingbirds, Animal-plant relationships, Pollinators, Quirky

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:

Apparently 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 or from the Queen of the Tropics website (click on Fertilizer, Insecticide, and Pruning).

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.

Valerie Easton, a local garden writer, mentioned several bird-attracting plants when she reviewed a Bellevue wildlife garden. Her article can be found at: http://seattletimes.nwsource.com/pacificnw/2003/0504/living.html

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. This information 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:
"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, 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: 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:

Washington State University has basic information about growing Kiwi.

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 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 2 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 (in left menu select "Tree Fruits" then "Plum")

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, "Digging Rocks" 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. Here is the web address for Lewis’ article: http://www.ipm.iastate.edu/ipm/hortnews/1993/5-26-1993/plant.html

According to the MadSci Network, citronella oil may be more effective at repelling mosquitoes than the plant itself. Here is the web address for the article: http://www.madsci.org/posts/archives/sep2000/970199522.Bt.r.html

Lastly, the Colorado State Cooperative Extension recommends scented geranium, lemon grass and a host of other plants. Here is the web address: http://www.colostate.edu/Depts/CoopExt/4DMG/Pests/mosquit.htm

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: 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 oak leaf Hydrangea turning brown around the edges and falling off?

View Answer:

We do not diagnose plant problems, especially without a sample: we defer to the Master Gardeners who are trained in diagnosis. You can locate a Master Gardener Clinic within Washington State here.

However, based on my personal experience with my own Oakleaf Hydrangea, 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. I have cut most of them off. I have new growth showing on most all branches.

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, Phyllosachys, 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.

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 WSU Cooperative Extension. Click ORNAMENTALS, then RHODODENDRONS to see pictures and information on what to do.

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 Landscape Plant Problems by 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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June 24 2013 12:55:25