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

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

QUESTION:

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?

ANSWER:

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 Compost and Mulch Questions

Use of free cedar mulch in Round Rock, TX
March 17, 2013 - Round Rock provides city residents free mulch to pick up. It is all cedar apparently. I am turning my now dead, mostly clay, very alkaline and rocky thin soil front lawn into a bigger flower bed of mo...
view the full question and answer

Native shrubs or ground cover for north-facing landscape in Ft. Worth
March 23, 2010 - Need native plant ideas for a landscaping bed against the house facing north. Already has 1 Beautyberry but two others died of root rot last year due to incredibly high water table in our area. Old ...
view the full question and answer

Plants that will grow on the Connecticut coast
June 08, 2010 - I live on the coast in Connecticut and have a hard time growing plants here. I live about 1/2 mile from the beach and find that my soil is very rocky. The only plants that have done well in my yard ...
view the full question and answer

Area needing soil amendment in San Diego
December 02, 2009 - I have a dirt area in the corner where my fence comes together. The dirt is clay-like and during the winter the area gets very little, if any, sun and during the summer it gets 4-6 hours of sun. Wha...
view the full question and answer

Why is oakleaf hydrangea not blooming now in Irving TX?
July 01, 2009 - I live in Irving Texas and have an oakleaf hydrangea. It bloomed in the early spring and now it is not blooming. Is there anything I can do to get to bloom?
view the full question and answer

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