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.
Excerpt:
“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.
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.
Typical bloom time for the Yoshino cherry trees (Prunus x yedoensis) in the Quad is mid- to late-March, but timing is weather-dependent. You can check the UW Cherry Cam, which they update each spring: https://www.washington.edu/video/campus-webcams/
This article shows the stages of flower development and provides additional detail about the factors affecting bloom time. Here is another article about research into predicting bloom time.
Excerpt:
“The timing for peak bloom — meaning 70% of buds have emerged — varies each year based on weather conditions that the developing buds are exposed to in January, February and March.
“”‘In order to reach peak bloom, buds need to accumulate a certain number of both cold and warm days, known as ‘growing degree days,’ said Marlee Theil, a UW graduate student in the School of Environmental and Forest Sciences.”
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.
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
Douglas Justice of the University of British Columbia Botanical Garden is the author of “Ornamental Cherries in Vancouver”. Published by the Vancouver Cherry Blossom Festival, this excellent guide celebrates a rich collection of urban flowering cherries, some 40,000 trees as of the 125th anniversary of the city in 2011.
Ornamental cherries are a major component of the Washington Park Arboretum, especially along Azalea Way. This book’s photographs include close-ups of flowers and an example of the tree in a landscape. Leaves are described as they emerge, in the full leaf of summer, and as they color in the fall. Sadly, this book is hard to obtain (we are still hoping to add the 2014 edition to the Miller Library) and is not available to borrow and take with you strolling in the Arboretum next spring.
However, there is much to learn from a visit to the library. For example, the Yoshino cherry (Prunus x yedoensis ‘Somei-yoshino’) is of uncertain origin, but is famous for the Hanami (cherry viewing) festivals in Japan. This is also the cherry of the Tidal Basin in Washington, D. C. and at “The Quad” on the University of Washington campus. Another widely planted selection is the Kanzan or Kwanzan cherry (Prunus Sato-zakura Group ‘Kanzan’), perhaps because the “apparent good health of this cultivar often borders on the miraculous.”
Excerpted from the Fall 2018 Arboretum Bulletin.