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?

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

Friday - June 24, 2011

From: Round Rock, TX
Region: Southwest
Topic: Turf
Title: Roots of live oak in lawn from Round Rock TX
Answered by: Barbara Medford

QUESTION:

I live on a cul-de-sac and have a small triangle shape yard. There is a large live oak in the middle of the yard. I am concerned because large bark covered roots have emerged on two sides of the tree. The roots are so large, I am unable to use my lawn mower around them. Is my tree in trouble? Should I forego grass and landscape around the roots? Thank you.

ANSWER:

Yep, that's what oak roots do. Your tree is not in trouble, but your lawn probably is, and we can't guarantee that planting anything else under there will be successful, either.

Given the choice between having great trees and having ground cover under them, we would vote for the trees every time. And it's necessary to remember that most tree roots occur in the upper 12" of soil, and may extend three times the dripline of the tree. Oak roots also form a mat beneath the soil, which discourages any other plant. Planting within the dripline can damage the roots of the tree, and the understory plant probably doesn't have a chance of competing anyway. The Lady Bird Johnson Wildflower Center recommends only plants native to North America and to the area in which they are being grown, as these are adapted by millions of years of experience to the soil, annual rainfall and temperatures of that area. We still can't guarantee that any plants you might choose would even survive beneath your trees, and you may decide to simply cover the bare ground with a good quality shredded hardwood mulch. This will have to be replenished from time to time, but as it decomposes, it will add nutrients to the soil, and improve the soil texture, as well as protecting the tree roots from heat and cold.

There is also the problem of the shade the tree casts. We consider full sun to be 6 or more hours of sun a day, part shade 2 to 6 hours of sun, and shade less than 2 hours of sun a day. Finally, there is the question of allelopathy. Various studies have demonstrated that oaks can have allelopathic affects on surrounding plants. Allelopathy is the production of plant inhibiting chemicals by one plant to regulate the growth of others in its vicinity. One important group of chemicals produced by oaks is tannins. They are produced in leaves and litter and also directly by root systems in soil. Tannins are inhibitory to many organisms. Salicylic acid and other organic acids are also produced by oaks and are toxic to other plants. Allelopathy is species specific for the oak in question and the species that is inhibited.

So, bottom line, no, don't try to mow over those roots. In fact, keep machinery away from your tree, remembering that damage to the bark can cause sap to leak out, which is an invitation to the nitulidid beetle, a carrier of the oak wilt fungus.

 

 

More Turf Questions

How to make a lawn into a prairie in Arlington, Texas
September 15, 2010 - I am removing lawn grasses in order to start a native prairie meadow. After grass removal, I'll put down 1/2" of compost. I will broadcast wildflower seeds on the compost. If I mulch after broadcas...
view the full question and answer

Did my neighbor's zucchini affect my apple tree from Oak Lawn, IL
October 26, 2009 - My neighbor planted zucchini plants near a flowering non-fruit producing apple tree in my yard. Soon afterwards in July the tree began to shed leaves. Could the zucchini plant have caused this?
view the full question and answer

Is installing irrigation with Habiturf a good idea in Round Rock Texas?
December 05, 2011 - Mr. Smarty Plants, I am in the process of planning a new lawn in my front yard. We have decided to plant the Habiturf seed mix (thank you, by the way). Originally, we planned on installing a spri...
view the full question and answer

Invasive non-native Bermuda grass in lawns
July 30, 2007 - Hello Mr. Smarty Pants. My yard here in southwest Austin is the only lawn with Bermuda Tif 419 grass. I am surrounded by neighbors with St. Augustine. I upgraded to this hybrid Bermuda for a number of...
view the full question and answer

Drought tolerant grass with little need for mowing for Hill Country of Texas
November 17, 2011 - What grass would you recommend for the hill country of Texas that is drought tolerant and does not need frequent mowing?
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
© 2014 Lady Bird Johnson Wildflower Center