Host an Event Volunteer Join Tickets

Support the plant database you love!

Q. Who is Mr. Smarty Plants?

A: There are those who suspect Wildflower Center volunteers are the culpable and capable culprits. Yet, others think staff members play some, albeit small, role. You can torture us with your plant questions, but we will never reveal the Green Guru's secret identity.

Help us grow by giving to the Plant Database Fund or by becoming a member

Did you know you can access the Native Plant Information Network with your web-enabled smartphone?

Share

Ask Mr. Smarty Plants

Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.

Search Smarty Plants
See a list of all Smarty Plants questions

Please forgive us, but Mr. Smarty Plants has been overwhelmed by a flood of mail and must take a break for awhile to catch up. We hope to be accepting new questions again soon. Thank you!

Need help with plant identification, visit the plant identification page.

 
rate this answer
Not Yet Rated

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

More Trees Questions

Growing Magnolia trees in Palm Desert, CA.
October 02, 2012 - Will magnolia trees grow in the Palm Desert/Indio, CA area?
view the full question and answer

Growth rate of the American beech tree from West Hartford CT
May 25, 2010 - What is the growth rate of an American beech tree?
view the full question and answer

Moderate-sized trees for lawn in West Virginia
August 10, 2014 - I recently had a landscape design completed by a professional lanscape company. The landscape is sloping down in front of my house. At the corner they included a Sweet Bay Magnolia, which we like ve...
view the full question and answer

Disappearance of leaves on desert willow in Tucson AZ
August 08, 2009 - We have a Lois Adams Desert Willow (Tucson, Az). The leaves will pump out and then a day or so later, all of the leaves are gone. The only bugs we've seen on it are very, very small ants. Could this ...
view the full question and answer

Need advice for pruning a young Bur Oak tree in Austin, TX.
November 02, 2010 - I grew a beautiful bur oak from seed, and three years later it is now taller than I am. I hate to cut anything off this tree and hurt it, but there are two branches that are rubbing together and growi...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.