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
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

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 Problem Plants Questions

Black Walnut tree in LA
March 12, 2012 - I was just given a black walnut tree and am trying to determine where to place it. I’ve read on your site that “Certain plants will not grow under Black Walnut trees because of the juglones that the ...
view the full question and answer

Plants to replace Phragmites australis (Common reed) in Cedar Ridge Preserve
February 25, 2015 - Dear Mr. Smarty Plants, I live in the DFW area and volunteer at a preserve (Cedar Ridge). We are constantly battling the common reed, Phragmites australis, around the pond. I am wondering what shou...
view the full question and answer

Poison ivy? vine in NJ
July 30, 2012 - I have a vine growing among some vegetation in my backyard. It has a leaf with 3 "points" with ridges along its edges. The smaller leaves are reddish which is why I thought poison ivy but definite...
view the full question and answer

Disposal of bulbs to control Arrowhead aquatic plant
August 29, 2006 - How can I kill Arrowhead permanently? I have sprayed repeated years with Roundup, Crossbow, etc., but the arrowhead comes back from the bulb the next year!
view the full question and answer

Defense against poison ivy from The Woodlands TX
March 24, 2014 - Hi and thank you in advance for your help. My husband is allergic to Poison Ivy, Oak, Sumac, or something in our yard. We need someone who is very knowledgeable to come and identify any poisonous pla...
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 | STAFF
© 2015 Lady Bird Johnson Wildflower Center