En Español

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

Tuesday - September 04, 2012

From: Austin, TX
Region: Southwest
Topic: Problem Plants, Erosion Control
Title: Exposed Tree Roots in Austin
Answered by: Brigid & Larry Larson

QUESTION:

I have a large ash tree with a lot of mud at the top of a sloping yard. I want to build a small retaining wall with the ground leveled above. This would entail covering exposed tree roots with 4-18 inches of dirt. Will this hurt the tree?

ANSWER:

Mr Smarty Plants is a bit mixed on your question.  Common knowledge has it that it is harmful to a tree to cover its roots,  yet if the roots are exposed anyway it is tempting to cover them a bit.

  This article from the Colorado Extension describes the root mass,  both that it extends beyond the tree crown and that the majority of the action is within 6 to 24” of the surface.

  The issue with covering the roots involves compaction of the soil.  The article above states  ”Changes in soil depth around trees can also cause injury to root systems.  The addition of only 4 to 6 inches of soil over a root zone drastically reduces the amount of oxygen and water available to the roots”

  A great solution to your desire is to build a “Tree Well”, where the roots are covered with very coarse rock or mulch to preserve their air and water access.  This publication from the West Virginia Extension states 18” as the depth where plain dirt fill would be too deep.  It gives excellent recommendations on building a tree well.

 

From the Image Gallery


Green ash
Fraxinus pennsylvanica

Texas ash
Fraxinus albicans

Arizona ash
Fraxinus velutina

More Erosion Control Questions

Wind and erosion tolerant plants from Austin
August 05, 2013 - I recently cleared a fire break by removing cedar from around my home in West Austin. I'd like to plant the exposed NW facing slope with native shrubs and trees. Looking for selections that can wit...
view the full question and answer

Deer Resistance and Erosion Control for St. Louis County MO
January 03, 2014 - I am looking for deer and rabbit resistant native plants for erosion control on a steep ravine slope with part sun and part shade in St. Louis County MO.
view the full question and answer

Full Sun, Wind-Tolerant Shrubs and Vines for Steep MN Hillside
June 26, 2013 - My neighbor and I share a very steep, large (in total almost 200 ft. wide) west-facing hillside in Excelsior, MN on Lake Minnetonka. We both have a flat grass area at the bottom so the hillside does n...
view the full question and answer

Native plants for controlling erosion in Fairmont WV
August 30, 2010 - I'm interested in finding native plants, either perennials or grasses, that would help control erosion on a fairly steep slope. The area is partly shaded.
view the full question and answer

Landscaping recommendations for site in Dubuque, IA
March 27, 2010 - I need a seed recommendation. Here are the variables: Location: Dubuque, IA (east Central Iowa) Soil type: Sandy to sandy and gravelly. Part is a riverbank facing east. Steep bank then flat to ...
view the full question and answer

Support the Wildflower Center by Donating Online or Becoming a Member today.
E-NEWSLETTER | BECOME A MEMBER | DONATE NOW | MEDIA | JOBS | SITEMAP | STAFF INTRANET
© 2016 Lady Bird Johnson Wildflower Center