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?


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

Thursday - March 21, 2013

From: Houston, TX
Region: Southwest
Topic: Xeriscapes, Compost and Mulch, Grasses or Grass-like, Trees
Title: Surface tree roots hurting grass in Houston
Answered by: Barbara Medford


We have 2 mature Arizona Ash trees in our yard (30-40'). One of them is in a sunnier location and has developed an extensive network of surface roots (up to 1 to 1 1/2" Dia.) between the tree and the house during our drought killing the grass in that area. Can we cover those roots with sod, or better yet strip them out and lay new sod in that area without damaging the tree?


No. Often we are tempted to leave it at that when we have to make a negative response to a question, but we always try to at least make some explanation. Sometimes our only answer is we don't know. In this case, we have to say which comes first, the grass or the tree? Covering tree roots with more than about an inch of soil will be suffocating to the roots and they will promptly push up again. Most tree roots are near the surface because of the need for moisture and also the gas exchange of oxygen and carbon dioxide at the surface. Covering them with grass sod, same problem. Stripping out the roots, worst.  The roots are down there to gather nutrients and moisture from the soil. These substances are passed up stems and trunks to the leaves which, utilizing sunlight through the process of photosynthesis, manufacture food for the whole plant, transporting it back down the trunk or stem to the roots, where nutrition for the whole plant is stored. Those roots are where they need to be for the tree to survive.

In addition, we suspect that part of the problem for your lawn grass is, as you mentioned, the drought conditions and part is the shade from those trees. There are few lawn grasses that can tolerate much shade, and those that can are mostly water guzzlers. It would be your choice, of course, but we are all in favor of the trees.

We would suggest you consider putting something else beneath those trees and perhaps embark on a process of xeriscaping. From eartheasy, here is an excellent article on Xeriscape. Obviously, you do not have to do every single thing suggested for xeriscaping, but you can start small and work your way up. Without knowing exactly what else is going on in your garden, we would suggest covering the offending roots and bare ground with a nice layer of mulch. Please read our How-To Article Under Cover with Mulch.

A good quality shredded bark mulch will make a nice cool surface for the ground, sheltering the tree roots from heat and the sun, discouraging weeds from sprouting and preserving moisture in the soil. It will tend to scatter or decompose, sinking into the soil and making it healthier, over time, but it's an easy fix to spread some more on the area. And it doesn't have to be mowed. We had one letter from a homeowner this week that said they were so over grass, and we feel, in this hot, dry climate, that may be a very good idea.

Follow this plant link, Fraxinus velutina (Arizona ash), to our webpage on it to learn more about its needs and growing conditions. You might also be interested in the fact that, according to this USDA Plant Profile Map of its distribution, that the Arizona Ash is not even native to the southeast area of Texas where Harris County is located.


More Grasses or Grass-like Questions

Central Texas native plants good for cut flowers in Austin
March 15, 2010 - What are the best native plants to Central Texas that can be used as cut flowers for indoors in the home? I have a large garden that will be partly vegetables, partly for cut flowers. Thank you for ...
view the full question and answer

Cutting Juncus effusus back from Bellevue WA
November 18, 2010 - I read your posts about Juncus effusus and just have one follow-up question. When is the best time to cut them back to the ground - before winter or early spring? I live in the Pacific NW. I recent...
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

What is Andropogon saccharoides?
August 06, 2008 - I am reading Roy Bedichek "Adventure with a Texas Naturalist" I came across a reference to sage grass (Andropogan saccharoides)p. 23. I searched the data base and didn't any infromation abou...
view the full question and answer

Habiturf installation after Take-All fungus
January 24, 2012 - Are other soil remedies needed (besides those listed in your Habiturf brochure) to install Habiturf on land which had a St. Augustine lawn which was decimated by take all patch.
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.
© 2015 Lady Bird Johnson Wildflower Center