Experts tackle readers’ garden questions.
Q: Our 10-year-old healthy birch tree only got leaves on the west side; no leaves on east side. The birch in our backyard looks normal. I see this and leafless-next-to-leafy birches around town. Is it drought? Dying birches?
Joanie Fleetwood, Galt
Master gardener Cathryn Rakich: Stately groves of three or more birch trees are a well-known sight in the Sacramento region. One of the most common in this area is the European white birch, famous for its papery white bark scattered with black, irregular-shaped grooves.
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Healthy birch trees can live 25 to 40 years, so a 10-year-old tree has many good years ahead.
However, birch trees also are susceptible to several problems, including lack of water, wood-boring pests, root damage, sunburn and herbicide drift, all of which become evident with bark damage, yellowing and spotted foliage, and/or leaf drop. It is important to note that declining trees often show signs of dying on only one side initially.
Birch trees, which prefer moist soil, have suffered greatly due to the drought. In the Central Valley and other hot locations, adequate irrigation is essential. While water conservation is important, it is critical to keep trees irrigated and healthy.
Trees should be watered deeply at the drip line about once a week in the dry, hot season. Remember to add a 2- to 3-inch layer of mulch, at least 6 inches from trunk, to conserve moisture.
Drought stress also can lead to attacks by wood-boring insects. Birch trees are a common host for the larvae of several species of borers. Dying limbs, rough or gnarled bark, trunk and branch swellings, sap exudation and sawdust-like frass (excrement) are indications that wood-boring insects have infested a tree.
For more information on managing these pests, visit the University of California Integrated Pest Management website at http://ipm.ucanr.edu/PMG/PESTNOTES/pn7477.html.
Root damage also can lead to undersized, discolored and prematurely dropped leaves. Branches die, often beginning near the top of plants, and eventually the entire plant can be killed. Root damage can result from improper cutting, girdling or lack of water, as well as root rot or root fungus disease.
Tree trunks should be checked for sunken areas, which are a likely indication of root damage. Proper irrigation and adequate drainage are essential to avoiding root damage.
Birches can get sunburned. This injury to above-ground plant parts, including leaves and bark, is caused by excessive exposure to solar radiation. Sunburn can cause leaf discoloration and death to many species of trees, including birch, which have thin, delicate leaves.
Leaf drop on only one side of a tree also suggests a directional application of a toxic material resulting in what is known as herbicide drift. Has the homeowner or a neighbor recently applied a pest or weed killer? Herbicides and insecticides should be properly applied to the target plant or site when they cannot move onto other plants. Pesticides should not be sprayed during windy conditions when they can be carried into areas where they can harm non-target plants.
For more information on the correct use of pesticides, check out “Pesticides: Safe and Effective Use in the Home and Landscape” on the UC IPM website at http://ipm.ucanr.edu/PMG/PESTNOTES/pn74126.html#ENVIRONMENT.
Cathryn Rakich is a UC Cooperative Extension Master Gardener for Sacramento County.
Questions are answered by master gardeners at the UC Cooperative Extension services in Sacramento and Placer counties. Send questions to Garden Detective, P.O. Box 15779, Sacramento, CA 95852. Send email to firstname.lastname@example.org. Please put “Garden Detective” in the subject field and include your postal address. To contact UC Extension directly, call:
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