Managing drought stress in trees and shrubs

Summer is slowly coming to an end and severe drought conditions continue to persist. Throughout the season, our lawns, trees and shrubs have been feeling the heat. Without supplemental watering or adequate rainfall, prolonged dry weather has caused devastating damage to many Louisiana gardens.

Water is essential for plants to thrive. Along with sunlight, water is needed for photosynthesis, the metabolic process in which plants make food, to occur. When water becomes scarce, the photosynthesis cycle may be disrupted. In trees and shrubs, the disruption of this cycle can cause significant damage, potential die-back or even death of the plant.

Trees and shrubs experiencing drought stress may exhibit effects in a few different ways. When experiencing a moisture deficit, foliage may change from a dark green color to a light green color. Inevitably, without relief from rainfall or watering, the leaves will turn brown and drop. In response to drought conditions, wilting or drooping of leaves may also occur. This is primarily due to the negative effects of high temperatures on dehydrated cells within the vegetation of the plant.

Once experiencing the strain of a water shortage, vegetation may be more susceptible to pests and diseases. Diseases such as cankers, root rots, wood rots and wilt are more prevalent during and after drought conditions. Drought-stressed trees may also fall prey to pests such as wood-boring insects. This could significantly damage trees and shrubs, making it difficult for them to recover. Additionally, it is not recommended to perform any heavy pruning during warm, dry weather conditions, seeing moisture stress may make it difficult for the tree to heal and “scab over”.

Supplemental watering during dry conditions is the best way to mitigate drought stress. The LSU AgCenter recommends that a general rule of thumb is to apply 1 inch of water per week. The best practice for watering during a drought is to do so deeply and less frequently to encourage deep root growth. To limit evaporation and ensure efficient watering, it is important to water during the hours of 6 p.m. to 8 a.m. when temperatures are cooler.

Although we (unfortunately) cannot control the weather, it is important to recognize the signs of drought stress and best management practices to minimize damage. For more information or additional inquiries, please contact the area Horticulture and Livestock Extension Agent, Alli Spillman Decell, at or call the office at 225-336-2416.

Photo 1. Azalea shrub experiencing significant dieback from lack of adequate moisture caused by drought conditions. Photo by Alli Decell/LSU AgCenter

Photo 2. Lawns and ornamental grasses exhibit signs of drought stress earlier than trees and shrubs due to their shallow root structure. Photo by Alli Decell/LSU AgCenter

9/8/2023 5:17:56 PM
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