P&PDL Picture of the Week for
March 7, 2011

Flooding and Trees

Gail Ruhl, Senior Plant Disease Diagnostician, Purdue University

Are your trees treading water with the recent deluge of melting snow and rain? The natural question is how long can trees survive flooding before injury results? According to Jeff Iles, Extension Horticulturalist, Iowa State University, the prospect for survival and continued growth is good if flood waters recede in seven days or less. However, if flood waters cover roots of sensitive trees for longer periods, symptoms of injury such as leaf chlorosis (yellowing), downward curling of leaves, leaf drop, and branch dieback may occur.

Following the recession of flood waters, saturated, poorly-drained soils will continue to pose a great hazard for trees, since oxygen is unavailable to roots in waterlogged conditions. Another hidden danger that may result from flooding is the deposition of sediment over tree roots. Silt and sand deposited over feeder roots to a depth greater than three inches may impede movement of oxygen to tree roots, especially on small or newly-planted trees. If feasible, sediment should be removed.

Recovery practices include enhancing the vigor of flood-stressed trees by following proper tree maintenance practices and eliminating additional stress. Fertilization is not a cure or remedy for root injury caused by flooding. Dead or severely cankered branches should be removed as soon as possible; other corrective pruning should be done during the dormant season.

Aerating the soil, mulching, and watering during extended dry periods are recommended practices that may help enhance vigor, but they are not rescue treatments for severely injured trees. For future landscaping plans, avoid planting sensitive species in flood-prone areas.

For more information on flooding and trees, go to:

Understanding the Effects of Flooding on Trees (pdf file)- Iowa State University

Flooding and Its Effects on Trees (USDA Forest Service)

Landscape Plants for Moist to Slightly Moist Areas HO-226 (pdf file)

Landscape Plants for Wet Areas HO-227 (pdf file)

 

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Wabash River flooding the Lafayette Municipal Golf Course (2003)

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service