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 Compost and Mulch Questions

Non-native Podocarpus macrophyllus in Ft Worth TX
November 12, 2011 - I know this question does not pertain to a native plant but I've spent too much time not finding an answer to my question. I have many mature Podocarpus macrophyllus bushes at my house I purchased in...
view the full question and answer

Chlorosis in yaupon from San Angelo TX
April 08, 2012 - Thank you for your information on the yaupon holly. We just finished clearing out the mulch and the red ground cover that popped up. I will quit watering it as much as the rest of the plants. Our y...
view the full question and answer

Holding an Acer rubrum in a container for two years
October 10, 2008 - Dear Mr. Smarty Plants, I am thinking about ordering a Red Maple tree that is cultivated from Mount Vernon. I appreciate the historic nature of such a tree. The tree will be shipped to me and is ...
view the full question and answer

The Pros and Cons of Using Stone Mulch for Plants and Wildfire Safety
December 04, 2013 - I am trying to grow native plants that are wildfire-resistant. I want to avoid the use of flammable mulch -- especially in beds next to the house. I'm considering river rock or crushed stone, but one...
view the full question and answer

Watering needs for a new landscape
October 11, 2008 - How much and how frequently are you supposed to water after implementing a new landscape? For example, perennials and succulents that are drought tolerant.
view the full question and answer

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