Issue: March 4, 2000

Do tree roots grow after the tree is cut?

My tree is 34-years-old and has found its way into my sewer line. Unfortunately, after $800 in drainage bills, the tree has to go. How do I uproot my tree and its roots?

This question is one that concerns many people. However, it should not be a problem. Once the tree has been cut, the roots cannot grow anymore because the leaves are necessary to provide the food to fuel root growth. If the roots continue to produce sprouts with leaves, then in time there may be more root growth. The simple solution to this problem is to remove any sprouts that develop from the roots as soon as they begin to grow. In fact, the production of these sprouts is to your advantage because in order to produce these sprouts, the tree must withdraw food stored in the root. As you remove the sprout, you rob the tree of that stored food and reduce the size of the root by reducing the food stored in it.

The sprouts may be removed manually by cutting them just below the soil surface, digging to remove them and a piece of the root to which they are attached, or by use of herbicides. Translocated herbicides, those which are absorbed into the leaves and translocated into the roots, will be more effective than the contact herbicides that kill only those plant parts with which they come into contact. If you use herbicides, read and carefully follow the directions on the label.

It is possible to use some herbicides before removing the tree to kill more of the root system more rapidly than by just cutting the tree. This is done by applying the herbicide to notches cut into the trunk, just deeper than the bark. Don't make the notches (called frills on the herbicide label) too deep. Your objective is to cut to the phloem layer which is just under the bark. The phloem is the tissue in the plant that carries food from the leaves to the roots. This is most effective in the autumn, though it will also work well if done in the summer. It is important that there be leaves producing food which is being translocated to the roots through the phloem. Look for herbicides labeled for this purpose. A few weeks after applying the herbicide the tree may be cut.

Root problems are worse in older types of sewer systems composed of tiles or tar paper rolled to form pipe. These systems are prone to leakage which attracts the roots to the pipe and provides the roots a means of entrance into the pipe. Newer plastic sewer pipe is less subject to root problems since, if properly installed, it will not leak and attract the roots. There is still a chance that a root will grow along side the pipe. As the root grows in diameter, it may then crush the pipe, cracking it, and allowing leakage and root entry into the pipe.

Send your gardening questions to Yard and Garden, ATTN: Dr. Curtis Smith, NMSU Cooperative Extension Service, 9301 Indian School Road, NE, Suite 112, Albuquerque, NM 87112. Curtis W. Smith, Ph.D., is an Extension Horticulture Specialist with New Mexico State University's Cooperative Extension Service. New Mexico State University is an equal opportunity/affirmative action employer and educator.