Native Plants

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.

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Wednesday - May 30, 2012

From: Austin, TX
Region: Southwest
Topic: Planting, Trees
Title: How close can house be built to live oak from Austin
Answered by: Barbara Medford

QUESTION:

We have a healthy 21" live oak tree on our lot and are planning to build a home in Circle C subdivision in southwest austin. The home foundation will be within 15' of the large live oak. Need your help assessing the following: 1. Is there a risk of moving/expanding root system causing foundation cracking in future ? What is a safe distance away from the live oak tree to build a home ? 2. Are tannins and other chemicals given out by live oak trees a problem to growing a lawn or other plants under the tree's canopy ?

ANSWER:

This is a question we get over and over, so we are going to refer you to some previous Mr. Smarty Plants Questions for some of the other answers.

Okay, we are sure you get our drift, and please don't shoot the messenger. You will have to make some hard decisions about where on your lot your house can be located, or if the tree is in danger of having to be removed to protect the house. We have given you a lot of information, but we can't make the decision for you.

In reference to Question No. 3, here is an extract from another former Mr. Smarty Plants question:

"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."

In other words, it depends on which plant and which oak, and we don't have lists of plants that will grow under specific species of oak."

And then, of course, there is the shade cast by a healthy live oak, which also affects negatively the growth of plants beneath it.

From the Image Gallery

Escarpment live oak
Quercus fusiformis