En EspaŅol

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
Can't find the answer in our existing FAQs, submit a question to Mr. Smarty Plants.
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

Stem canker or leaf fungus in Morella cerifera
June 14, 2007 - Dear Mr.Smarty Pants: The upper half of our wax myrtle, which we had allowed (with artful pruning) to reach about ten feet suddenly died this spring (it dropped most of its leaves and didn't sprout...
view the full question and answer

Problems with Thuja in Oakland CA
December 16, 2010 - I have a Thuja hedge about 100' long. Part of this hedge and a well established Rhododendron have been diagnosed with Armillaria mellea that is spreading. I see the bunches of mushrooms growing eve...
view the full question and answer

Freeze-damaged Texas Mountain Laurel in Austin, TX.
May 05, 2011 - I have a Texas Mountain Laurel (Sophora secundiflora) that is several years old. During this past winter, one of the freezes we had split one of the largest trunk right below the soil line. T...
view the full question and answer

Yellowing of palm tree leaves
May 14, 2008 - I want to know about palm trees. The leaves are turning yellow.
view the full question and answer

Advisability of trimming oak trees in August
July 13, 2007 - In general,what is your opinion on pruning oak trees in August? If it is positive, should the extreme moisture of this year affect the timing?
view the full question and answer

Smarty Plants's Facebook profile Support the Wildflower Center by Donating Online or Becoming a Member today.

Mr. Smarty Plants wants you to be his Facebook friend. Click the Facebook icon to add yourself to Mr. Smarty Plants list of friends.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | SITEMAP
© 2014 Lady Bird Johnson Wildflower Center