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February 9, 2013

1 - Large trees in confined areas are sometimes best removed and replaced with trees whose size better adapts them to the location.

Yard and Garden February 9, 2013

Q.
There is a lovely Ash tree, about two stories high, growing in my small front yard over a small patch of sparse, not-so-healthy grass (see photos attached). In spite of the tree's beauty in the warmer months, I have been contemplating removing the tree entirely. What concerns me are the large exposed tree roots extending toward the sidewalk, driveway and house. I am concerned they will eventually destroy the slab, sprinkler system and anything else in their way. In addition, exposed tree roots make mowing the grass almost impossible. To solve the mowing problem, I would like to replace the grass with groundcover or gravel, but the Internet tells me that covering the roots or cutting them out will kill the tree.

Would you please advise me? Should I remove or keep the tree? If I should keep it, what should I do with the area beneath it?

Pam G.

Albuquerque

A.
Your question expresses a concern of many homeowners. It is obvious that tree roots can cause problems. We see the damage to sidewalks and driveways and worry about the foundations of our home. Based on the photographs you sent, you have too large a tree for the size of the lawn area. There is a second complicating factor in that the soil is so compacted that the tree roots must grow on the surface. This is not good for the tree, and bad for the lawn.

I usually prefer to save a tree if possible. The shade and value added to a landscape make a tree very valuable, but in your case, tree removal appears to be the way to avoid problems in the future. The driveway and sidewalk are at risk. The home foundation will probably not be harmed unless there is a leak under the foundation. Roots will not grow into areas of dry soil found under homes in our arid environment. If the lawn were to be overwatered so that water seeped under the house, or if there were leaks in the plumbing under the foundation, then it is possible that the roots could grow under the house. The exposed roots of the tree in the lawn create mowing problems and also put the tree at risk. The exposed roots experience excessive heat in the summer and extreme cold in the winter. They need the protection of soil over them, but what you read is correct, it is not good to add soil over the roots. A groundcover would solve the mowing problem, but not the potential problems associated with roots damaging the driveway and sidewalk.

Removal of the tree will be best in your situation, but replacement with a smaller tree (at maturity) with less potential for damaging pavement. Flowering trees such as hawthorn, crabapple, or desert willow are a few of the trees that can be used as replacements. When replacing the tree, it would be wise to deeply rototill or dig the soil over the whole lawn area to reduce the compaction that forces the roots to grow on the surface and makes it difficult to properly irrigate both the tree and the lawn. In preparing the soil in this manner you must take care not to damage underground utilities and the irrigation system. This work to reduce soil compaction will damage the lawn. You can replace the lawn with grass or with a groundcover. Considering the issues we face in New Mexico regarding water conservation, maximizing the efficiency of the irrigation system for either the new lawn or groundcover will also be wise and assure success for the renovated landscape.

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