Rent Shop Volunteer Join

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 Diseases and Disorders Questions

Western soapberry dropping leaves in San Antonio
June 03, 2013 - My Western Soapberry tree (China berry?) Suddenly started dropping full, perfectly healthy green, leaf units. Now half the tree is turning yellow. There is a second tree in the yard not far from this ...
view the full question and answer

Juniper as host of cedar-apple rust
July 17, 2007 - Thanks for the helpful advice on the Eastern Red Cedar. I was wondering if you could ease my mind about a potential problem. I have read up on some of the native plants in my area in a very good book ...
view the full question and answer

Need help with Wheeler's Dwarf Pittosporum
September 02, 2015 - We have about five Dwarf Wheeler Pittosporum plants. All of them are mature and were doing well. I was on vacation for a week or so and when I came back I saw of each of them is plant 90% dead. The d...
view the full question and answer

Use of surfactants with herbicide for water
January 05, 2008 - I read the article on frogs and the use of Rodeo. Your answer was correct, but to the best of my knowledge, Rodeo is approved for use near water only because it lacks a surfactant. When surfactant...
view the full question and answer

Red-backed bugs on mountain laurel (Sophoro secundiflora)
May 12, 2010 - I found red-backed bugs (in fact two end-to-end like the east Texas love bugs) on my mountain laurel which has been losing leaves. Are these bugs the culprit?
view the full question and answer

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