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PAL Questions: 830 - Garden Tools: 346 - Recommended Websites: 680

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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.

These suggestions are from two sources, which you might want to review to learn more:
The Oregon State University Extension Service website has several articles on tomatoes including one on variety selection, which may give you better success next year.

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 a March 2003 WSU Extension article on heirloom apples, for example.

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

New York University's Langone Medical Center has information about the plant's medicinal uses, as well as some words of caution about drug interactions (with anti-coagulants and anti-hypertensives). 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 website. You will need to use the search bar on the left side of the page for ornamental plant diseases.

To have a sample from your Japanese maple diagnosed, you can take samples to a free Master Gardener Clinic, or you can send samples to WSU Puyallup Research and Extension Center (for a fee)at: www.puyallup.wsu.edu
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 insect and diseases (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 Lamiastrum, a closely related plant which is very aggressive. 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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June 24 2013 12:55:25