Elisabeth C. Miller Library

Gardening Answers Knowledgebase

Search Results for: Prunus | Search the catalog for: Prunus

Plant Answer Line Question

Keywords: Rhamnus purshiana, Pyrus, Nyssa, Hovenia, Oxydendrum arboreum, Cornus nuttallii, Malus, Crataegus, Native plants--Care and maintenance, Quercus, Prunus, Acer

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


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

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

Date 2019-09-19
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Plant Answer Line Question

Keywords: Berberis, Skimmia, Leucothoe, Fatsia, Euonymus, Elaeagnus, Shade-tolerant plants, Osmanthus, Aucuba, Viburnum, Shrubs, Prunus, Camellia, Buxus

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


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

Date 2019-09-19
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Plant Answer Line Question

Keywords: Plum, Aphids, Prunus

My prune tree has tons of aphids in the leaves (also a lot of ladybugs to eat them but I am not sure the ladybugs will win out). Do I need to try to rid the tree of the aphids? If so how?


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

Date 2019-05-17
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Plant Answer Line Question

Keywords: Prunus, Fruit--Diseases and pests

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?


We can only guess from your description, and in order to get an accurate diagnosis you will need to take a sample (including both healthy and affected parts if possible) to a Master Gardener clinic. Click on the appropriate link for your local clinic through Master Gardeners / Washington State University Extension.

Meanwhile, for information about common diseases of plums in the Pacific Northwest, try searching Washington State University's HortSense website.
The symptoms you describe are similar to 1. Crown gall, 2. Black canker and 3. Black knot. Click on those diseases for descriptions, photos, and control methods.

You can also take a look at pages like this one, on black knot of ornamental cherry and plum, from Morton Arboretum. See if the images resemble what you are seeing on your tree.

Date 2019-09-11
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Plant Answer Line Question

Keywords: Vaccinium, Prunus, Plum, Failure to fruit

We have three blueberry bushes of different varieties that have been bearing just fine over the last several years. This year one of them bloomed heavily and looks like it's generating a good crop. The other two only had a few flowers. What could account for this? Is there anything we should be doing to encourage blooming and fruiting?

I am also wondering when we will ever see fruit on the Italian Prune tree I planted several years ago. It was already pretty big when we bought it, and now it is about 2 inches caliper near the base and is about 12 feet tall. Is there anything we can do to encourage some fruit on this? I do not even remember seeing it bloom this year. Could it have something to do with the weather patterns?


One problem might be a lack of bees. There could also be other reasons, such as Botrytis blossom blight, and blueberry shock virus.

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

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

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

As for the Italian prune, a plum tree may not begin to bear until it is 3 to 6 years old.

You may also want to visit a Master Gardener Clinic with your questions. You can locate a Master Gardener Clinic within King County on this website.

Date 2019-11-07
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Plant Answer Line Question

Keywords: Prunus mume, Prunus

I would like to know how well the following trees will do in the Seattle area ?
(1)Prunus mume var. 'Matsubara Red'
(2)Prunus 'Kiku-shidare-zakura'


Both species you mention should do well in the Seattle area. Prunus 'Kiku-shidare-zakura' is described in Arthur Lee Jacobson's Trees of Seattle (2006). Its other common name is 'Cheal's Weeping Cherry.' The Japanese name means "weeping chrysanthemum cherry." Its form is arching and weeping from the point where it has been top-grafted. According to Jacobson, the tree tends to be gawky and a bit sparse, but the flowers are very double. It is common in Seattle.

Prunus mume is also listed in Jacobson's book. This tree and its cultivars (such as 'Matsubara Red') are less common in Seattle. You might be able to see examples in the Seattle Japanese Garden, the Kubota Garden, or Seattle Chinese Garden.

Because the common name of Prunus mume is Japanese apricot, there is sometimes confusion between Japanese flowering cherries and apricots. Prunus mume does produce fruit, but they are small and "bland to somewhat bitter," and in Japanese cuisine they are preserved in salt and used as a condiment (Umeboshi plum). The more familiar fruiting apricot tree is actually Prunus armeniaca (and its cultivars).

Date 2019-09-27
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Plant Answer Line Question

Keywords: University of Washington, Flowering cherries, Flowering trees, Prunus, Garden tours

I would like to know when most of the beautiful flowering trees will be in bloom on the University of Washington campus this spring? I would like to bring a tour group to see them.


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

Here is an excerpt from an article from the UW Alumni magazine about that garden:
"The Grieg Garden is the reverse of what folksinger Joni Mitchell once sang about they 'unpaved' a parking lot and put up Paradise. Until the renovation of the HUB [Husky Union Building] Yard in 1990, the space south of Thompson Hall was for cars. Today it is for people (and squirrels). One of the UW's newest beauty spots, the Grieg Garden is a cozy clearing surrounded by trees and flowering shrubs. Located on the north side of the HUB Yard, it is best in the spring, when rhododendrons and azaleas frame the space in drifts of lavender, crimson, magenta and pink."
-Tom Griffin

Date 2019-04-12
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Plant Answer Line Question

Keywords: Flowering cherries, Prunus

I have an area in my garden where I would like to plant a cherry blossom (Prunus). However there are telephone and power wires above so I would like the tree to reach no more than 15 feet in maturity. Are there any dwarf or smaller growing varieties?


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

  • Prunus serrulata 'Shogetsu' reaches 15 feet tall, by 22 feet wide.
  • Prunus x 'Hally Jolivette' reaches about 15 feet.
    Here is an article by Wayne Winterrowd in Horticulture Magazine (May 1, 2007) with additional information about this tree, which he refers to as the "loveliest of trees," and the best of the flowering cherries..
  • Date 2019-04-06
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    Plant Answer Line Question

    Keywords: Prunus, Fruit--Diseases and pests

    For three years, my plum tree has had leaves that curl and shrivel somewhat. I have heard of aphids causing leaf curl in plums, but I don't see many aphids.

    I also have a peach tree that has "Peach Leaf Curl" or Taphrina deformans and the symptoms on the plum leaves look similar to that. Here is what I wonder:

    • The peach and plum are at least 100 yards apart. Is it really possible that the peach infected the plum?
    • With the peach tree the fruits are also affected but with the plum fruits do not appear to be affected.
    • Are peach and plum affected by the same diseases?


    Both peach and plum trees are in the genus Prunus. Your plum tree's problem sounds like plum pockets and peach leaf curl, which are caused by fungus (usually Taphrina).

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

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

    Here is Oregon State University's online guide to plant diseases (aimed at professional gardeners) This is Washington State University's site intended for home gardeners.

    I don't know if your plum could have gotten the same species of Taphrina fungus that is affecting your peach (i.e., Taphrina deformans), but the conditions in our climate are probably ideal for this type of fungal disease. University of California, Davis says that the pathogen which causes peach leaf curl survives on tree surfaces and buds, and is enhanced by wet spring weather.

    From University of Nebraska Plant Pathology:

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

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

    Date 2019-10-02
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    Plant Answer Line Question

    Keywords: Flowering cherries, Trees--Diseases and pests, Prunus

    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?


    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.

    Lime Sulfur Fungicide

    Copper Sulfate

    Date 2019-05-18
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    Plant Answer Line Question

    Keywords: Failure to flower, Pyrus, Corylus, Prunus

    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?


    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."

    Oregon State University Extension has fruit pollination charts, and there is an example from Burnt Ridge Nursery for European pears. At the very bottom of the webpage linked below, you can find Raintree Nursery's pollination charts for various fruits and nuts.

    General information from University of Vermont Extension on failure to flower and failure to bear fruit from Washington State University Extension.

    Date 2019-08-23
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    Plant Answer Line Question

    Keywords: Plant diseases--Control, Prunus, Fruit--Diseases and pests

    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!


    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.

    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)[formerly available online] 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 is one of the most effective fungicides for control of peach leaf curl and is allowed in certified organic production . Bordeaux and copper fungicides are also approved for certified organic programs and 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.


    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.

    Date 2019-04-25
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    Plant Answer Line Question

    Keywords: Prunus, Allelopathy

    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?


    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 North Carolina State University 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 potentially allelopathic tree species and Prunus laurocerasus is not among them.

    Date 2019-09-27
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    Plant Answer Line Question

    Keywords: Prunus, Fungi and mushrooms, Fungal diseases of plants

    I have a 50-year-old Italian plum tree. The limbs have oyster-shaped growths on them. These growths will not come off--they are hard. Is it a fungus or disease? Or is the tree just getting old?


    Hard fungal growths on trees are called conks, a type of bracket fungus, and they are not a good sign. According to The Sunset Western Garden Problem Solver, these growths "indicate a hazardous condition from decay inside." Usually by the time they are seen, decay inside the tree is substantial and you may need to get an arborist's help to keep the tree from breaking and dropping branches, and to assess whether it is a danger to structures or people. The Pacific Northwest Chapter of the International Society of Arboriculture provides a listing of local certified arborists. You can also get an arborist referral from Plant Amnesty.

    Date 2019-10-31
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    Plant Answer Line Question

    Keywords: Plant diseases--Control, Prunus, Pesticides and the environment, Pesticides

    We live in a heavily treed (fir and cedar mostly) condominium complex. Our shrubs are sprayed twice a year by a professional spraying company to protect against fungus and other problems. We are thinking of spraying every other year to save on expenses.

    Would we be jeopardizing the health of our shrubs and small cherry trees by doing so?


    Unless your shrubs and trees have a history of trouble with diseases, I can't think of any reason they should be sprayed at all. Even if the plants were susceptible to disease, a more sustainable approach than annually applying fungicides and other pesticides would be to select disease-resistant plants that will thrive in your garden's conditions without that sort of intervention.

    Spraying, depending on what is being sprayed, can be a hazard to human health and the environment. You may be able to stop your spraying program entirely by instituting good garden practices, like cleaning up debris and providing good air circulation around the trees, and avoiding overhead irrigation.

    Examples of nonchemical ways to manage fungal problems that may affect ornamental cherry are provided below, from Washington State University Extension's HortSense website:
    "Brown rot is a fungal disease which initially infects the flowers. The petals turn light brown, develop water-soaked spots and may have tan or grayish areas of fungal spores. Infected flowers often remain attached to the plant, spreading the disease to small twigs and branches. Infected twigs and branches are often observed in the summer as flagged, dead leaves and twigs. Infected branches develop cankers which may produce gumming (leaking sap) or may girdle and kill the branch. Most brown rot cankers develop with a dead twig at the center where the initial branch infection occurred. Fruit can also be infected, dry out, and hang in the tree. Tan or gray fungal spores may be found on infected blossoms, fruit, or twig cankers. Ornamental and fruiting stone fruit trees are affected.
    Select Non-chemical Management Options as Your First Choice!!

    • Avoid wounding trees.
    • Clean up and destroy fallen flowers and other debris beneath trees.
    • Remove and destroy all infected twigs and branches during the summer, making pruning cuts well below infected tissues."

    Similarly, here are their recommendations for managing Coryneum blight or shothole:

    • Avoid overhead watering, as leaves must be moist for infection to occur.
    • Prune and destroy dead buds and cankered twigs if present.
    • Rake and destroy infected leaves.

    Again, for cherry leaf spot:

    • Avoid overhead watering. If overhead irrigation is necessary, limit it to times when foliage can dry quickly.
    • Rake and destroy all fallen leaves and debris under trees.
    • Space plantings and prune to provide good air circulation.

    Date 2019-09-21
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    Plant Answer Line Question

    Keywords: Vaccinium, Rubus, Prunus, Insect pests, Fruit--Diseases and pests, Fragaria, Berries--Diseases and pests, Berries

    Could you tell me more about a new type of fruit fly that is supposedly infesting fruit here in the Pacific Northwest? Which fruit are affected?


    The fruit fly is called the Spotted Wing Drosophila. It is known to affect strawberry, raspberry, blueberry, plum, peach, cherry, and grape. Oregon State University has created an information clearinghouse about this pest. Here is their information for home fruit growers. Washington State University has also devoted several web pages to this fly. Here is their Integrated Pest Management information, excerpted below (SWD stands for Spotted Wing Drosophila):
    "Monitor for SWD using traps. [...] These vinegar traps are for monitoring purposes only and will not provide control of SWD. Remember, chemical control is not necessary if SWD is not present.
    Composting fruit will likely not be effective at destroying maggots and pupae.
    Remove infested and fallen fruit. Destroy or dispose of infested fruit in a sealed container.
    Management recommendations are currently being developed for this pest. For the time being, good sanitation practices should be used."

    Whatcom County Extension has clear, basic information for home gardeners as well. Since this insect is a relatively recent invader in the Northwest, information is constantly being adjusted and research is ongoing.

    Date 2019-10-31
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    Plant Answer Line Question

    Keywords: Pyrus, Malus, Tree identification, Prunus

    Is it possible that I'm seeing cherry trees flowering this early (mid-February)? Some have white flowers, and some are pink.


    It is certainly true that things may be flowering early when we have a mild winter. In 2014, the famous cherry blossoms in the University of Washington's Quad began opening on March 13, and the winter of 2015 has been warmer, so they may be opening earlier than that. While it is possible you are seeing flowering ornamental cherries (Prunus species), they are easily confused with their cousins in the same genus, flowering ornamental plums--extremely common street trees in Seattle--most of which are definitely flowering now. Ornamental pears (Pyrus) are also flowering now. They have white petals, and might be mistaken for cherry trees as well but the distinctive odor of pear blossoms is a big clue to their true identity: acrid, astringent, and just plain stinky! Seattle's City Fruit website has a guide to spring-blossoming ornamental and fruit-bearing trees that is helpful.

    The Vancouver Cherry Blossom Festival offers some pointers on how to tell the difference between cherry and plum blossoms. Most cherry blossoms aren't noticeably fragrant, while plum blossoms are fragrant. Cherry blossoms usually have small splits or indentations at the ends of their petals. Note, however, that the book Japanese Flowering Cherries by Wybe Kuitert (Timber Press, 1999) says cherry "petals are mostly [emphasis mine] retuse," that is, not all of them have a shallow notch or split on the ends of the petals.

    Project BudBurst, a citizen-science phenology project, has information on identifying cherry trees. There is also a guide to telling the difference between cherry and apple blossoms (apple blossoms have 3 to 5 styles whereas cherries have one). And what is a style? It is the part of the pistil between the stigma and the ovary.

    According to the British Natural History Museum, one unifying characteristic of cherries is "flowers in clusters with stalks all arising from a central point, or arranged along a short stem, or in spikes."

    Date 2019-03-14
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    Garden Tip

    Keywords: Juglans, Gleditsia, Prunus, Pruning, Cornus, Birch

    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:

    Date: 2007-05-17
    Link to this record (permalink)

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