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September 28, 2013

1 - You have option in managing problems with tree roots damaging your patio.

Yard and Garden September 28, 2013

Q.

I have a beautiful Chinese pistache tree that has roots growing towards my home. Those roots are breaking the concrete patio. Is it possible someone could evaluate the tree and recommend the best course of action? I would like to save the tree, if possible.

A.

It is a good idea to have a knowledgeable person come to evaluate the situation. A good person to contact regarding the problem with your tree is your local NMSU County Extension Service agent. The agent can evaluate the location of the tree and discuss with you options available, whether cutting roots, installing a root barrier, or tree removal. NMSU Extension Service Master Gardeners and some of the staff from local nurseries can also provide information regarding your concerns.

Most gardeners have seen the effects of roots growing under concrete and pavement. As those roots enlarge they are able to crack or even lift up the concrete. Yet, as gardeners we often fail to consider how far we must plant the tree from the patio or pavement to avoid this problem. When we first plant small trees, it seems they are far enough from the pavement. We have a hard time imagining the root system of the tree as it matures, and of course, we want the full benefit of shade as soon as possible. The result is damaged concrete and a risk for the tree.

In the case of a mature tree, there are several options. The last, and least desirable, option is to remove the tree and replace it with another tree farther from the patio or choosing a replacement plant that will not cause a problem.

Cutting the roots of the tree may be an option, but that depends on the size of the roots and the distance of the tree from the patio. Cutting the roots is not a preferred outcome if it is necessary to cut one or more large roots. Such roots are conducting water and nutrients from numerous smaller roots to the main body of the tree. Removal of the large root removes a large percentage of its water and nutrient supply. In addition, these roots are important in supporting the tree, preventing it from falling and doing damage to a structure, patio furnishings, or to a person. An on-site evaluation considering the location of the tree and the potential for damage now and in the future is important.

If there is sufficient distance to allow cutting a root that does not create severe damage to the tree, then this option may be considered. However, new roots will probably form from the cut root (if it was not too large), and these roots may grow toward the patio. In time the problem may reoccur. To reduce the potential problem, there is a product that creates an underground "fence" that the roots have difficulty crossing. This material is a spun-bonded polypropylene fabric to which is attached plastic dots with treflan herbicide. This herbicide does not translocate through roots to the tree and kill the tree; it only stops the roots from growing in the area of the herbicide. This fabric may be placed into a trench just outside the patio, toward the tree. The roots will try to grow down and under this barrier, so at the base of the trench, turn the bottom foot or so of the fabric back toward the tree to redirect the roots back toward the tree, away from the patio. Avoid seams and overlapped fabric in this area as the roots may find the seams and penetrate the barrier. This is a useful technique for people planting young trees to reduce the chances of the roots growing under a patio, driveway, or other paved area. It is always better to avoid a problem.

For more gardening information, visit the NMSU Extension publications Web site at http://aces.nmsu.edu/pubs/_h, or to read past articles of Yard and Garden go to http://aces.nmsu.edu/pubs/periodicals.html

Send your gardening questions to:

Yard and Garden, Attn: Dr. Curtis Smith
NMSU Agricultural Science Center
1036 Miller Rd.
SW, Los Lunas, NM 87031.

Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist emeritus with New Mexico State University's Cooperative Extension Service. NMSU and the U.S. Department of Agriculture cooperating