Friday, February 27, 2009
Tree talk: Kwanzan Japanese flowering cherries and English boxwoods
John Arbogast
Landscape consultant John Arbogast answers your questions every Thursday. Send questions about your lawn, garden, plants, or insects to:
Dear John
5102 Greenfield St. SW
Roanoke, Va. 24018
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Q: We planted a young flowering kwanzan cherry tree close to our one-story ranch style house a few years ago since it looked good there in a group of some little holly bushes under one of our windows. Now that this tree has grown, it needs some special pruning, I guess. Every time the wind blows, some of the flowering cherry branches rub against the window, so something needs to happen now. What should we do?
A: Cut it down. Pruning will make it look ugly.
The Kwanzan Japanese flowering cherry tree can be a beautiful spring tree, but if it is growing close enough to a house to be rubbing against a window, major pruning on the house side could weaken the tree to the point that it could split off on its heavy side under a heavy load of ice or snow.
A temporary measure would be removing up to one-third of leaf-producing branches from throughout the tree. Removal of more than that reduces the amount of leaves a tree needs to nourish itself. You don't want it to stave to death. Cutting ends of its branches now will remove flowers the tree this spring, but it sounds like you don’t have much choice.
You'll eventually come to the conclusion that you must chop it down and plant something else. When you do, apply a brush-killer product on the stump to kill the roots and prevent resprouting.
Q: I need your advice on what’s happening to my mature boxwoods (English Boxwoods, I think) that I have lined up in front of my brick house interspersed with some azaleas. Two of the boxwoods on one side of the front porch have shown scattered orange and brown leaf discoloration on outer portions of branches but the adjacent azaleas look good as do the few other boxwoods in front of the house. I have leaves from the nearby trees piled up at the bases of the boxwoods and azaleas as I was told that this natural mulch was good for them. This area of landscaping in front of the house is long but not very wide. There is only a small piece of lawn there before natural woods begin. Is this the beginning of that dreaded English Boxwood Decline disease?
A: If the boxwood leaf discoloration does not extend all the way from the ends of the branches into the center of the plants, I don’t believe you have the beginning of English Boxwood Decline root disease. This outer leaf discoloration symptom suggests high humidity in the area, in part because of the leaves you've mulched at the bases of the boxwoods. It sounds to me like dampness held against trunks is a culprit. I cannot explain why only two of your boxwoods have shown discoloration rather than all of them in the front of your house.
My recommendations:
- Rake out all the leaves.
- Prune all the discolored branch ends of the boxwoods and cut back sides of all the boxwoods by 6 to 10 inches to stimulate new growth.
- Fertilize the azaleas when they finish blooming.
- Don’t add nutrients to the boxwoods and do not add mulch around the boxwoods this spring.
