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

ACER (maple):
A. buergeranum (trident maple)
A. campestre (field maple)
A. ginnala (Amur maple)
A. circinatum (vine maple)

CORNUS nuttallii (western dogwood):

CRATAEGUS (hawthorn):
C. douglasii (black hawthorn)
C. monogyna
C. phaenopyrum (Washington thorn)
C. x lavallei (Carriere hawthorn)

HOVENIA dulcis (Japanese raisin tree)

MALUS fusica (Pacific crab apple)

NYSSA sylvatica (black gum)

OXYDENDRUM arboreum (sourwood)

PRUNUS (prune/plum/cherry):
P. virginiana var. melanocarpa (chokecherry)
P. emarginata (bitter cherry)

PYRUS (pear):
P. communis (common pear)
P. pyrifolia (Chinese pear, sand pear)

QUERCUS (oak):
Q. acutissima (sawtooth oak)
Q. imbricaria (shingle oak)

RHAMNUS purshiana (cascara)

Season Winter
Date 2006-05-23
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The closest list I could find to meet your needs is one of evergreen shrubs that will grow in shade:

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

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

Season All Season
Date 2006-07-18
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From what the experts say, Cornus kousa grows 20—30 feet high and wide in cultivation. They can grow to twice that size in the wild.

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

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

Also, the Backyard Gardener website has a list of fastigiate trees. It doesn’t list their widths, but the links are helpful.

Season All Season
Date 2008-01-17
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The question of whether to control aphids in your prune tree really depends on how bad the infestation is and if the tree is otherwise healthy enough to outgrow them. Often infestations like aphids are a symptom of a larger problem. The tree may be stressed out by root competition from grass or too much or not enough water, too much or not enough nitrogen. A stressed out tree is attractive to aphids, who in turn attract lady bugs. My own mature prune tree gets covered in aphids every year. The leaves get distorted, and lady bugs come in droves. Some years I get a good harvest and some years I do not. I choose not to worry about it (I have other plants to fuss over). But if you feel the need to do something, see this website from WSU, then select Tree Fruits > Plum, Prune > Aphids.

Season All Season
Date 2008-01-17
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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. 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.

Locate a Master Gardener Clinic within Washington State.

Meanwhile, for information about common diseases of plums in the Pacific Northwest (search "cherry.")

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.

Season All Season
Date 2006-12-08
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Here is information from Washington State University Extension on the failure of plants to fruit, although it sounds as if you should not have major problems with fruit development, since you have three different blueberries which should pollenize each other, and your Italian prune should be self-fertile. The only problem might be a lack of bees.

Here is a page from Oregon State University which has some good general information on growing blueberries

Is it possible that the blueberries have become dense and twiggy? If they are not pruned, they may become unproductive. The information below is from University of Florida Cooperative Extension:

Pruning mature blueberry plants is largely a matter of cane removal or cane thinning. The objective of pruning mature bushes is to stimulate the proper balance of vegetative and reproductive growth, and limit plant size. Pruning stimulates the development of new canes which are more productive than older canes. A general rule is to remove about 1/4 to 1/5 of the oldest canes each year (usually one to three of the oldest canes). This will result in continuous cane renewal so that no cane is more than three or four years old. Pruning to reduce the number of flower buds may also be required on some southern highbush cultivars which set heavy crops such as 'Misty'. Flowers should always be removed from one and two-year-old plants by pruning or rubbing them off before fruit set occurs. Most pruning is usually done immediately after harvest during the early summer. Removal of some of the flowers buds to adjust the crop load is usually done during the late winter just before growth begins.

Season Spring
Date 2007-04-03
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There is long-standing confusion in taxonomy and nomenclature of Japanese flowering cherries and apricots but, to make a confusing story short---yes, both varieties you mention will do well in the Seattle area. In fact, both can be seen at the Washington Park Arboretum.
For hours, locations, etc. visit the Arboretum website.

Season All Season
Date 2008-01-31
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There is actually a "Tree Tour" of the University of Washington campus, called the C. Frank Brockman Memorial Campus Tree Tour, but it does not focus on flowering trees. I would recommend that you bring the group when the Yoshino cherry trees (Prunus x yedoensis) in the Quad are in bloom later this month (mid- to late-March). The Quad is also near the Grieg Garden, by Thompson Hall, which is an attractive spot. Here is an article from the UW Alumni magazine about that garden.

GRIEG GARDEN

The Grieg Garden is the reverse of what folksinger Joni Mitchell once sang about—they "unpaved" a parking lot and put up Paradise. Until the renovation of the HUB [Husky Union Building] Yard in 1990, the space south of Thompson Hall was for cars. Today it is for people (and squirrels). One of the UW's newest beauty spots, the Grieg Garden is a cozy clearing surrounded by trees and flowering shrubs. Located on the north side of the HUB Yard, it is best in the spring, when rhododendrons and azaleas frame the space in drifts of lavender, crimson, magenta and pink. On its teak benches—right out of a Smith and Hawken catalog—you will often find young couples holding hands or harried graduate students taking a break from the library. Dominating it all is a bronze bust of Norwegian composer Edvard Grieg. Originally cast for the Alaska-Yukon-Pacific Exposition of 1909, a group of Scandinavian fraternal societies gave the sculpture to the UW in 1917. For many years he rested in front of the old Meany Hall; later he was placed in the HUB Yard. Today he is the centerpiece of this garden, but he has a mystery surrounding him. Grieg's nose lacks the patina on the rest of the statue—it is ever shining. Could it be true that one fraternity requires its members to polish the nose as a rite of passage?
—Tom Griffin

Season Spring
Date 2007-01-18
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Here are two suggestions for smaller flowering cherry trees, from a list in Trees & Shrubs for Pacific Northwest Gardens (2nd ed.) by John A. Grant and Carol L. Grant (Timber Press, 1990):

• Prunus serrulata ‘Shogetsu’ reaches 15 feet tall, by 22 feet wide.
• Prunus x ‘Hally Jolivette’ reaches about 15 feet.
  Here is a Forest Service fact sheet with additional information about this tree, which sounds ideal for your space requirements.

Season All Season
Date 2007-01-18
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Keywords: Fruit--Diseases and pests, Prunus

PAL Question: I have a problem with a plum tree that I am unable to identify. The problem has existed for at least three years. The symptom is that the leaves curl and shrivel somewhat. The plum tree was planted seven years ago and another was planted near it six years ago to act as a pollenizer. Both are putting on good growth each year. I have heard of aphids causing leaf curl in plums. There aren't large numbers of aphids that I can see on this tree. I see some aphids on occasion but not in the numbers that would produce such a massive leaf curl on the whole tree.

I also have a peach tree that has "Peach Leaf Curl" or Taphrina deformans and the symptoms on the plum leaves look similar to that. However there are differences. There are a number of points and questions about this I am unclear about:

• The peach and plum are at least 100 yards apart and so I think it unlikely contamination would occur, but of course it is possible if carried via pruning equipment or some similar transport vehicle.
• With the peach tree the fruits are also affected but with the plum fruits do not appear to be affected.
• I have done some internet investigating and while all sites describe Taphrina deformans as a peach tree pathology none make any clear statement that it is confined only to peach trees nor mention other fruit tree varieties capable of getting it.
My internet research turned up a "Tree Fruit and Berry Pathology Diagnostic key" published by Cornell University. The key states it is for diseases common to Northeastern and the Mid-Atlantic region of the US. However, the portion of this diagnostic key relating to plums doesn't seem to fit the symptoms I experience.

So my questions are:

1. Can Plums get Taphrina deformans?
2. Can you hypothesize another pathology for my plum based on the symptoms I described?
3. Can you point me to a diagnostic key similar to the one Cornell has published but for the West coast diseases and fruits and perhaps published by WSU, OSU or elsewhere?

View Answer:

Your plum tree's problem sounds a bit like plum pockets, which is caused by Taphrina communis. Here is a link to an image

From Iowa State University Plant Pathology:

Have you noticed lately that your peach leaves appear curled or puckered? Do leaves appear to be lighter than normal, flushed with red, blistered, distorted, and curled? Chances are your tree has peach leaf curl, a fungal disease caused by Taphrina deformans. Although peach leaf curl is primarily a disease of peach, nectarines are also affected. Peach leaf curl is first noticed in spring when young leaves start to emerge. The entire leaf or a portion of it may appear crinkled and curled with flushes of red or purple . Later on in the season, the fungus begins to produce spores and leaves appear silvery or powdery gray. Infected leaves turn yellow and brown and fall off the tree and are replaced by a new set of foliage. Flowers, young fruits and stems may also be infected. Affected fruits are distorted with wrinkled, discolored areas on the surface. Extensive defoliation may affect fruit yield the following year and may also predispose the tree to winter injury and other diseases.

Plum pocket is a disease in plums caused by Taphrina communis. Leaf symptoms are similar with peach leaf curl and the plums appear to be distorted, wrinkled, and puffy. This disease is not considered a serious problem in most commercially cultivated plum varieties.

Here is Oregon State University's online guide to plant diseases. This is Washington State University's comparable site.

I don't know if your plum could have gotten the same form of Taphrina that is affecting your peach, but it sounds as if the conditions in your garden and in our climate may be ideal for this type of fungal disease. University of California, Davis says that the pathogen which causes peach leaf curl survives on tree surfaces and buds, and is enhanced by wet spring weather.

From University of Nebraska Plant Pathology:

Plum Pockets is very similar to the well-known disease peach leaf curl. It reached epidemic proportions on plum in the 1880's and sand cherry in the 1940's. The disease is still common today but rarely has an economic impact on stone fruit production. However, its unique symptoms always seem to peak the interest of individuals who are seeing it for the first time. The disease is caused by two species of Taphrina. Taphrina communis (Sadelbeck) Giesenh. has a worldwide distribution. Its hosts include plum (Prunus angustifolia) and several wild Prunus spp. found in America. Taphrina pruni primarily infects European plums and is rarely found in America. The disease cycle of Taphrina communis is similar to that of Taphrina deformans (peach leaf curl). The fungus overwinters as conidia on twigs and bud scales. Infection generally begins at bud break when these spores are rain splashed to susceptible green tissue. Leaves, shoots, and fruit are all susceptible but symptom development is most common on fruit. The fungus invades host tissue directly through epidermal cells. Once the fungus is established, a specialized mat of fungal cells (hymeneal layer) containing asci and ascospores forms. The asci are not protected by a specialized ascocarp. Ascospores are released, germinate and begin budding, much as a yeast does. Conidia (bud conidia) serve as secondary inoculum in the spread of the disease. Initiation of the disease cycle is favored by cool wet weather.

You might consider bringing in samples of the affected leaves to a Master Gardener Clinic for a definitive diagnosis. They may also have more information on whether the disease can pass from peach to plum, or whether your two types of trees simply have two different strains of the pathogen.

Season All Season
Date 2007-06-13
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Keywords: Prunus, Trees--Diseases and pests, Flowering cherries

PAL Question:

We have a mature ornamental cherry or plum tree that suffered from brown rot last year. We removed all affected branches and leaves. We were told that we might need to do something else this winter or spring--spray the tree with something, possibly. Can you advise us on how to keep our tree healthy?

View Answer:

I consulted The Organic Gardener's Handbook of Natural Insect and Disease Control edited by Barbara Ellis (Rodale Press, 1996), and this resource recommends doing what you already did, by removing and destroying affected parts of the tree. At the beginning of the growing season (early spring) you can spray sulfur to control this fungal disease on blossoms. If you were growing fruit, you would spray again later in the season to protect the fruit, but since this is an ornamental tree, it isn't necessary. Copper sprays are also used to control the disease. Washington State University Extension recommends preventive measures, such as avoiding wounding trees (damaging bark with string trimmers/weed-whackers/lawnmowers, or making bad pruning cuts). Avoid wetting the blossoms and leaves, and keep the tree pruned for good air circulation in the canopy. Avoid excessive nitrogen fertilizer. While the tree is in bloom, check it frequently for symptoms, and destroy any diseased parts as soon as you notice them.

I found sources for less toxic (but still not hazard-free) versions of these fungicides from Peaceful Valley Farm & Garden Supply, but they may be available at your local garden center as well. Some of these require a pesticide handler's license.

BSP Lime Sulfur Fungicide

Basic Copper Sulfate

Season All Season
Date 2007-10-11
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Keywords: Prunus, Corylus, Pyrus, Failure to flower

PAL Question:

I planted numerous fruit trees about 7 years ago. These included almond, pear, apple, hazelnut, and plum. The almond and apple trees have done really well.

The pear, plum, and hazelnut trees have never even bloomed, let alone borne fruit. Am I doing something wrong or do I just need to be a little more patient?

View Answer:

All of your trees should be mature enough to flower and bear fruit, given the right conditions. There are many potential causes of failure to flower. Are your trees that have not flowered in a location that receives high nitrogen fertilizer (such as near a lawn)? This would lead to lots of leafy growth at the expense of flowers. Cold winter weather can also damage buds and lead to no flowers.

The lack of fruit could be due to lack of pollination in addition to the causes listed above. Do you have two or more pears (Pyrus) and hazelnuts (Corylus)? Is your plum (Prunus) a variety that needs a pollenizer, or is it self-fertile? Raintree Nursery has information on flowering and fruiting for Corylus that says"Two different varieties or seedlings of similar flowering period," are needed, and that "European Filbert flowers winterkill at -15 F. Others are hardier."

You can find a Pear pollination chart, a European plum pollination chart, and a Asian plum pollination chart at Raintree Nursery as well.

General information on failure to flower and failure to produce fruit is available from Michigan State University Extension, too. Another source on failure to produce fruit is from Penn State Department of Horticulture.

Season All Season
Date 2008-04-11
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Keywords: Plant diseases--Control, Prunus, Fruit--Diseases and pests

PAL Question:

Have you any advice about how to combat peachtree leaf curl using natural methods at this stage in the season? I've just read about the use of thyme or oregano oil, but no advice on amount used. I would be glad of any help!

View Answer:

The information I was able to find about thyme oil as a treatment for Taphrina came from an application to the U.S. Patents Office, so I cannot speak for its efficacy. I did find information from Connecticut Agricultural Experiment Station which mentions thyme oil as an organic-acceptable insecticide, and I also found an abstract from Australasian Plant Pathology about thyme oil being used on Botrytis.

The U.S. Department of Agriculture's Agricultural Research Service offers research on the use of plant essential oils in postharvest disease control,too.My impression is that the efficacy of these plant-based oils is still being studied and evaluated.

I also found information on managing peach leaf curl (Taphrina deformans) from the National Sustainable Agriculture Information Service which suggests using lime sulfur, acceptable by U.S. organic standards, though European standards may differ. Below is a more substantial excerpt:

The life-cycle diagram above in Figure 2 shows that the infection period for leaf curl is when new leaves start emerging from buds in the spring. Spraying after the buds have opened is ineffective, because infection takes place as the young leaves emerge, and the fungus develops inside the leaf.

Accordingly, sprays must be applied during the trees' dormant period—after the leaves have fallen and before the first budswell in the spring. Many orchardists spray just prior to budswell during the months of February and March. Orchards with a history of severe peach leaf curl benefit from a double application: in the autumn at leaf fall and again in late winter or early spring just before budswell.

Fortunately for the organic grower, lime sulfur—one of the most effective fungicides for control of peach leaf curl—is allowed in certified organic production . Bordeaux and copper fungicides—also approved for certified organic programs—are effective as well, but not as effective as lime-sulfur.

Pscheidt and Wittig (6), performed trials comparing Kocide™, lime-sulfur, several synthetic fungicides, and Maxi-Crop™ seaweed for leaf curl control. Lime-sulfur and one of the synthetics (ziram) were best, roughly twice as effective as Kocide. Seaweed sprays, despite positive anecdotal reports, were completely ineffective.

Severe leaf curl infection can cause the tree to shed many of its leaves and to replace them with a second flush of growth. At this time the tree will benefit from a light feeding with a quickly-available soluble fertilizer such as compost tea or fish emulsion to help it recover.

There are various levels of resistance to leaf curl among varieties; however, because of the relative ease of controlling the disease, breeding for resistance has not been a priority. Redhaven, Candor, Clayton, and Frost are some of the cultivars with resistance to leaf curl, though none is immune. In contrast, Redskin and cultivars derived from it are susceptible.

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The City of Seattle's Integrated Pest Management Solutions pages for landscaping professionals also suggests methods of prevention and control. Damage may be reduced by sheltering the tree from winter and early spring wet. If only a few leaves are affected, they may be removed by hand. Peach leaf curl does not usually kill the tree, though fruit yield will be reduced. This resource also mentions using copper fungicides and lime sulfur when the tree is dormant.

The Connecticut Agricultural Experiment Station has a factsheet on disease control for home peach orchards, including preventive steps to take.

Season All Season
Date 2008-04-30
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Keywords: Prunus, Allelopathy

PAL Question:

I have a laurel hedge that I am taking down. Can I use the chips as mulch or will the mulch kill things as I've heard that laurel is poisonous?

View Answer:

Is your laurel an English laurel? If so, it is the plant Prunus laurocerasus which does have toxic properties (cyanogenic glycoside and amygdalin, according to the information here from University of Florida Extension) but I think that the toxicity mainly affects people and other creatures if they eat its leaves, twigs or seeds. My guess is that the wood chips should be safe to use, but what you could do is use the mulch on a path or other area where you do not want plants to grow and it will not touch anything you will eat.

University of Georgia School of Forest Resources has a list of trees which are potentially allelopathic, and Prunus laurocerasus is not among them.

Season All Season
Date 2008-04-30
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Keywords: Birch, Cornus, Gleditsia, Juglans, Pruning, Prunus

Garden Tool: A common question gardeners have is when to prune. "When the shears are sharp!" is the often-heard answer. In reality there are a few timing guidelines that do matter.

First of all, certain trees are known to "bleed" when pruned while the sap is rising in late winter and early spring. Maples, dogwoods, birch, elm, walnut and honey locust are the most common.
Bleeding usually won't hurt the tree, but the pruning cuts are slower to heal which may leave susceptible trees vulnerable to infection. These trees should be pruned right after leaves fall off in autumn.

Cherry trees are at risk from the destructive cherry bark tortrix. The tortrix is attracted to fresh pruning cuts, so cherry trees should not be pruned between May and August when the tortrix is active.

Spring flowering shrubs should be pruned immediately after flowering so that the new growth has time to form next year's flower buds. Summer flowering shrubs may be pruned in winter because flowers are formed on this season's growth.

Pruning resources online:

• A short essay on pruning at the wrong time from Michigan State University Extension
• A good basic guide to pruning with illustrations from the US Forest Service
• A Google search of "pruning" limited to .edu sites (Cooperative Extensions links)

Season: All Season
Date: 2007-05-17
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