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Sunday - March 24, 2013

From: Dallas, TX
Region: Southwest
Topic: Compost and Mulch, Diseases and Disorders, Trees
Title: Allelopathy of American elms from Dallas
Answered by: Barbara Medford

QUESTION:

Are American elms at all allelopathic?

ANSWER:

There are four members of the genus Ulmus (elm) native to Texas and in or near Dallas County:

Ulmus alata (Winged elm)

Ulmus americana (American elm)

Ulmus crassifolia (Cedar elm)

Ulmus rubra (Slippery elm)

Black walnut isn't the only tree that produces juglone. This chemical is also secreted in smaller amounts by English walnut, hickory and pecan trees.Other trees with allelopathic properties include tree-of-heaven, sugar maple, hackberry, American sycamore, American elm, southern wax myrtle, cottonwood, black cherry, sassafras, red oak and black locust.

Certainly, in our experience, members of the Juglandaceae family (most familiar - walnuts, pecans) are the most prominent examples of allelopathy, but the American elm is definitely included as being able to deal with competing plants with chemicals. Please note that it is difficult to impossible to grow anything under any tree, including grass, because of the needs of the tree roots for moisture and nutrients from the soil and because of the shade from the tree. Here in Texas, we would vote for the trees and spread mulch under the shade of the tree. See our How-To Article Under Cover with Mulch.

From the Image Gallery

Winged elm
Ulmus alata

American elm
Ulmus americana

Cedar elm
Ulmus crassifolia

Slippery elm
Ulmus rubra