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LEAF DROP ON TREES REPORTED BY MANY CALLERS
I hope your summer garden is lush, full of color and totally devoid of problems. Go outside and enjoy it! Last weekend's rain (1.6 inches at my house) was what my father used to call "a million dollar rain." Prior to the weekend, my arms had been growing longer from carrying five-gallon pails of water to thirsty trees and shrubs.
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Last week set a record for phone calls about sick trees. Biggest problem is leaf wilt and leaf drop, particularly on ash trees. Similar problems were reported on maple, oak, walnut and willow.
The most likely cause of leaf drop is a fungal disease called anthracnose. The anthracnose fungus survives the winter in infected plant parts. During the spring and summer when the weather is cool and wet, spores are produced on infected tissues. These spores are spread by wind and splashing rain to buds, shoots, and expanding leaves.
This problem has been common in recent years when May is cool and damp. Anthracnose fungi cause blotches in leaves that can spread and turn the leaf yellow or brown. Many ash trees have suffered partial or total defoliation. Most will grow a new set of leaves in the weeks ahead.
In most cases, anthracnose does not cause permanent damage to established trees. Several fungicides are labeled for control but application to large trees requires special equipment to ensure adequate coverage and must be done repeatedly at bud break.
Anthracnose is most severe on the lower and inner portions of the tree. A more severe disease is verticillium wilt caused by the soil-borne fungi, verticillium dahliae.
One caller last week described a problem in a stand of mature maples that sounded like verticillium. Unlike anthracnose, verticillium often causes foliage and branches to wilt on one side or sector of the tree. If you suspect verticillium, consult with a tree service for an accurate diagnosis.
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By now it should be clear what plants in your yard suffered no-return winterkill. If your stressed trees and shrubs aren't popping new buds by now, they are probably dead.
A newspaper article last week described the unusual combination of factors that led to winterkill: "An early frost followed by last winter's extreme cold, ice storms, brilliant sun, early loss of snow cover and a long, cool, dry spring."
Look closely at your arborvitae and yew to see whether new foliage is emerging along stems and branches. If you can't see any activity, prune out the dead branches...or the entire plant.
I've noticed winterkill damage on many plants in my yard. At least a half dozen serviceberry seedlings planted last year didn't survive. Two blueberry bushes have sent new shoots out from near ground level but the upper branches are dead.
My azaleas bloomed only from buds protected under snow. A Royal Star magnolia planted last fall also had blossoms below the "snow line" but suffered bud die-back higher up.
Red twig dogwood that grows naturally in my yard was extremely slow to leaf out this spring. However, the new leaves have finally reached full size and some flowers appeared last week.
Best advice for your yard is to cut back any stems and branches that are barren and hope the plant fills in with new growth in the years ahead. If cutting out the dead tissue causes the plant to be more unsightly than you can bear, the only alternative is to dig it out and plant something new in that spot.
Trees and shrubs can be fertilized now with tree stakes, deep-root fertilizer or watered-in granular fertilizer. If you're not sure what method of fertilization is best for your plants, ask for advice at a reputable garden center and follow fertilizer label directions.
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PUTTING DOWN ROOTS:
A Delightful Blend of
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