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