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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 2018-04-11
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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 2018-03-15
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    Plant Answer Line Question

    Keywords: Flowering cherries, Pruning trees

    I live in Seattle. My condo board is having a debate about whether pruning an ornamental cherry after May will kill it or not. Can you help? Also, when should it be pruned?


    According to Cass Turnbull of the local organization, Plant Amnesty, the main reason pruning ornamental cherries is problematic is that the branch system of these trees is complex, and it is hard to tell (if you are not an experienced gardener or a professional arborist) what to prune. In her Guide to Pruning (Sasquatch, 2006), Turnbull says that ornamental cherries are prone to dieback if their branches are shortened. Besides the dieback issue, improper pruning can give rise to watersprouts (the branches grow straight up). I consulted two other pruning guides, both of which advised against any pruning of ornamental cherries.

    Do you know why the board wants to prune these trees? If the trees are too large for the site, it might make more sense to remove them and plant something appropriate which will not require risky pruning. You may find this discussion forum from University of British Columbia Botanical Garden helpful.


    "These generally disease susceptible trees resent severe heading back. Trying to force it to become a perfectly symmetrical shape will also destroy its natural character; much of the appeal of aged Japanese cherries (and related trees) is the contrast between the prettiness of the flowers and the rugged appearance of the trunk and branches."

    My summary is that, while pruning the trees may not kill them outright, it could make them aesthetically unappealing and more susceptible to disease, so it would be best to let them be.

    Date 2018-04-11
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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 2018-06-27
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May 31 2018 13:14:08