Native Plants
![](../_images/smarty_plants.gif)
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.
Did you know you can access the Native Plant Information Network with your web-enabled smartphone?
Ask Mr. Smarty Plants is a free service provided by the staff and volunteers at the Lady Bird Johnson Wildflower Center.
![](../_images/mr_smarty_plants_logo_web_200w.jpg)
rate this answer
![](../_images/star_00.gif)
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
More Problem Plants Questions
Eliminating Najas flexilis from a pond
December 22, 2014 - What method would be effective in eliminating Najas Flexilis from a pond?
view the full question and answer
Male or female Jatropha curcas from Brownsville TX
August 16, 2012 - How do know the sex of a young Jatropha C. plant? how many weeks before you can tell a boy/girl plant ?
view the full question and answer
Oak Sucker Reprise
May 02, 2015 - ----Original Question---- SUNDAY - JULY 06, 2014
Title: Live Oak Suckers Reprise, Austin TX
QUESTION:
Referring to an entry dated March 11, 2011 about Live Oak suckers - what happened to the su...
view the full question and answer
Can oleander poison the ground below it?
June 29, 2013 - Can oleander poison the ground below it? Would it kill/damage grass or other plants below it? Thanks.
view the full question and answer
Is Mimosa pudica poisonous from Janesville WI
February 21, 2014 - I have just recently learned of Mimosa Pudica also known as the sensitive plant. I see using the USDA website that it can be found in the USA so I think that covers the North America aspect. I have b...
view the full question and answer
Support the Wildflower Center by Donating Online or Becoming a Member today. |