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University of Illinois Extension

Has the Drought Damaged Landscape Plants?

October 3, 2012

The hurricane Isaac rains were very welcome and needed. "Unfortunately, they came too late for some trees and shrubs," says Rhonda Ferree, University of Illinois Extension educator, horticulture. "Several trees in the area dried up during our intense summer drought."

Ferree says that the 2012 drought could have a detrimental long term effect on your landscape plants. Young trees and shrubs often do not have well established root systems. "When a drought occurs, these plants cannot take up the amount of water needed to support the canopy of the plant."

"When the leaves lose more water than the root system can supply, leaf scorch usually occurs." In this situation, the leaves may turn brown starting at the edges and between the veins of the leaf. If lack of water continues, the leaves and shoots begin to wilt. The plant at this point may drop large numbers of leaves because the plant cannot continue to maintain them. You may even note early fall coloration of the leaves due to this water stress. Evergreen plants may suddenly turn brown resulting in the loss of the plant.

Ferree fears that the drought has also damaged plant root systems. "This can result in canker, sunscald and other diseases occurring on the plant a year or more after the damage has occurred." Many trees and shrubs that are lost from drought damage have shallow root systems or were growing in shallow, poorly drained clay soils.

How can trees and shrubs be protected during a dry period? If rain does not occur for a 3-week period, trees and shrubs planted in the last 3 to 5 years should be watered. Trees and shrubs should be watered once a week if there is no rainfall. A heavy complete watering is more effective than shallow

watering. Shallow watering will encourage shallow rooting which can lead to root damage during a severe drought.

Plants get most of their water from the soil surrounding their roots. The soil's physical characteristics largely govern the amount of water that it can hold and the amount available for plant use. This is why two similar plants located in different areas of the landscape may respond differently. One may need to be watered more often than the other. Keep in mind that failure to water landscape plants during a drought can result in the loss of the plants.

Many people feel that large trees won't be harmed by drought because they have large root systems. "This is not necessarily the case," says Ferree. She expects substantial tree dieback and death due to the drought over the next several years. "Many trees will take three years to die, and some will hang on until five years after the drought." As these trees decline, they are more susceptible to insect and disease infestations.

For more information on this or other horticultural issues, contact your local Extension office by visiting www.extension.illinois.edu. You can also post questions on Rhonda's facebook page at www.facebook.com/ferree.horticulture.


Source: Rhonda J. Ferree, Extension Educator, Horticulture, ferreer@illinois.edu

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