Flood Tolerant Trees

Some trees are able to withstand flooding, recover, and resume normal functioning. This trait may be of special interest to persons in areas of northern Illinois that had periodic flooding throughout June and July. Many native trees in river flood plains have proven their adaptive ability, but trees around recently constructed areas may not be capable of withstanding intermittent flooding. Flood-tolerant traits should be considered when selecting trees to save or to plant on flood-prone areas.

Flood tolerance varies with species. For example, green ash and silver maple are considered to be relatively flood-tolerant. Black cherry and several oaks can be injured by considerably less flooding and are said to be intolerant.

Flood injuries also vary. Early symptoms include leaf-tip and stem twisting, red coloration, chlorosis, and leaf wilting. Dieback of roots and twigs and the formation of dead spots in the bark may follow. If flooding continues the entire tree may eventually die. Some trees may not follow this pattern; leaf wilting can be followed directly by the death of the tree.

Trees often recover rapidly from slight injuries, such as twig dieback. With more severe injuries, recovery may take a year or longer. Reduction of vigor may render a tree susceptible to other adverse environmental conditions, such as insects, disease or drought. Proper pruning, fertilization and watering will help the tree recover.

Responses and tolerance of trees to flooding were studied extensively from the 1940s through the mid-1970s. These studies helped foresters understand the impact of flooding on trees, but it is still difficult to predict the adaptability of a species or an individual tree to a specific flooding situation. However, investigating the general tolerance of a type of tree before purchasing is a good practice for persons in flood-prone areas.

The University of Illinois has further information on selecting flood tolerant trees and proper tree care. Contact your local University of Illinois Extension office.

August - September 2000: Gypsy Moth: Know the Facts | Flood Tolerant Trees | Saving Seed from the Garden | Ideal Time for Lawn Renovation