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Drought Stress

June 8, 2005

Many areas of Illinois have been under light to moderate drought stress in the last couple of weeks. Drought is considered a noninfectious disease problem and can mimic other problems. Be familiar with symptoms that might result from lack of water.

Wilting is an obvious symptom of drought. This is something we recognize and which usually spurs us to action to provide water. The slow depletion of water to a plant may cause decline symptoms that elude us. These include scorching of leaf margins, dropping of leaves, death of young roots, death of branch tips, stunted growth, and eventually plant death. You can also kill plants with kindness. Avoid overwatering drought-stressed plants, as too much water in the root zone can also kill roots.

Report on Plant Disease, no. 620, “Leaf Scorch of Woody Plants,” is available in Illinois Extension offices. It can also be found on the Internet at http://www.ag.uiuc.edu/%7Evista/horticul.htm. This report discusses various factors that might cause leaf scorch. Water deficit is not always the culprit. Scorch might result from factors such as salt injury, lack of soil oxygen, sunburn, wind, chemical injury, or mechanical injury to the roots and trunk. Read this report for details.

Containerized plants may contain bark, peat, or other components that become hydrophobic once they dry down. In those cases, it may be difficult to re-wet the soil mix because water simply runs through the pot. Slow, progressive watering may be necessary to rewet such containers.

The amount of injury to a plant from drought depends on the severity of the drought, the duration of the drought, and the tolerance of the plant species. Some plants are very sensitive to lack of water. For instance, Japanese maples readily scorch in drought situations, whereas pin oaks can tolerate dry sites. The University of Illinois Extension “Hort Corners” Web site provides a means to search for trees that grow well in Illinois under various stress factors. Trees that tolerate dry sites are provided at