Plant Pathology Infobytes
September 28, 1999
Landscape & Woodland Trees - Drought Stress Apparent
As we go into the fall season, following an extremely dry summer, we are beginning to see an increasing number of trees in landscapes and woodlands showing signs of drought stress. While most trees are exhibiting few symptoms of the problem, some trees aren't holding up well from extended environmental stress.
Dogwoods have been particularly vulnerable to lack of water since this species tends to develop a relatively shallow root system. Consequently, soil moisture is depleted rapidly, and although dogwoods are "holding on," many are exhibiting severe leaf scorch, or browning of the entire foliage canopy due to water shortage.
In home landscapes, drought stressed dogwoods should receive irrigation with a soaker hose or sprinkler system. Most homeowners are aware soaker hoses should be placed so the water is applied to the tree's drip line area, and that a minimum watering period of 8 hours or so will be necessary to "re-wet" the root system to any appreciable degree. Affected dogwoods should be watered once a week until we receive our normal fall rains. If you have questions regarding tree irrigation, check with us at your county Extension office.
Other species, such as oaks, hickories, ornamental pears, maples, and magnolias are showing less severe drought stress, but trees growing on thin or light textured soils, which have poor moisture retention properties may symptoms of the disorder. Obviously, rainfall will do a lot more good than trying to water large trees with sprinklers or soaker hoses. However, it's apparent these trees need rainfall soon.
Drought stressed trees generally are more vulnerable to the effects of cold weather. To help reduce chances of cold injury to stressed trees this winter, consider adding a "winterizing" application of a fertilizer containing phosphorous and potassium. Avoid using high rates of nitrogen (no more than about 5%), since this fertilizer material should not be applied to drought stressed plants. Check with your county Extension office for a free copy of an information sheet on fertilizing ornamental plants and trees," for application information and advice on following this program for your landscape trees.
Infobytes newsletter was written by the late Dr. Frank Killebrew, Extension Specialist.