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P&PDL Picture of the Week

Flooding and Trees

Peggy Sellers, Purdue University
Adapted from an article by Jeff Iles in Iowa State University's Horticulture and Home Pest Newsletter (July 14, 1993)

With the recent flooding in much of the state, questions about the effect of flooding on trees have arisen. Most trees will escape injury if flood waters recede in seven days or less. However, if flood waters cover roots of sensitive trees for longer periods, injury symptoms such as leaf chlorosis (yellowing), downward curling of leaves, leaf drop, and branch dieback may occur. In a few extreme cases, trees may die.

Flood waters will eventually recede but soils will undoubtedly remain wet for a long time. Saturated, poorly-drained soils may pose the greatest hazard for trees, particularly if the waterlogged condition persists for an extended period. If oxygen cannot penetrate the roots, trees may exhibit symptoms associated with flooding. Warm, dry weather is the only cure for this chronic and potentially deadly soil condition. Another hidden danger resulting from flooding is the deposition of sediment over tree roots. Silt and sand deposited to a depth greater than three inches also may impede movement of oxygen to tree roots, especially on small or newly-planted trees. When possible sediment should be removed.

Enhance vigor of flood-stressed trees by following proper tree maintenance practices and eliminating additional stress. Dead or severely cankered branches should be removed as soon as possible; other corrective pruning should be done during the dormant season. Applying a low-nitrogen fertilizer, aerating the soil, mulching, and watering during extended dry periods are recommended practices that can help enhance vigor, but they are not rescue treatments for severely injured trees. Finally, avoid planting sensitive species in flood-prone areas in the event of future flooding events.

For more information on flooding and trees, go to:
Click on "flood damage."

Understanding the Effects of Flooding on Trees (IA)
http://www.extension.iastate.edu/Publications/SUL1.pdf (PDF 124K)

Flooding and Its Effects on Trees (USDA Forest Service)

Click on small image to view larger images.

Flooded Trees in Boone County Flooded Trees in Boone County
Flooded Trees in Boone County
(Photos by Steve Mayer, Marion County CES)

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Last updated: 4 June 2002/tlm.
The Plant & Pest Diagnostic Laboratory at Purdue University.