Issue: July 17, 2004

Trees removed but sprouts develop from roots

We have a persistent cottonwood stump that continues to send out sprouts. What is the name of a good product (herbicide or other) that will get to the remaining root system and stop any further growth?

I recently had a Chinese Elm tree removed from the back yard that was totally unmanageable for my property. The tree was cut and the stump ground to about a foot below the surface. I was very happy and began plans to grade and plant new vegetation. To my shock and within a month of the removal, little trees have sprouted everywhere in the yard. These little trees are sprouting at great distances from where the trunk once stood. The question I have is how to kill off the rest of the tree, including the buried roots. The root system is certainly not continuous any longer since the removal severed the roots in numerous locations. When I dug them up, I discovered that some of the saplings have sprouted from a few feet deep. This tree was over 4-1/2 feet in diameter, and the roots are extremely difficult to dig up.

I read that poison should have been applied directly to the trunk right after cutting the tree down and while it was still feeding. Now, several months later, it seems that since the roots are severed that wonât work.

It is interesting to receive basically the same question from two different states regarding two different trees. It is the same problem - the ability of some plants to regenerate from their roots. The elm usually does this after removal of the tree or injury while the cottonwood may often produce saplings at some distance from a living tree.

Dante is correct in his statement that a stump killer should have been applied to the stump as soon as it was cut (or even before cutting). The chemical (if the proper chemical was used applied as directed) would have translocated downward into the roots, reducing the ability of the roots to produce sprouts. This would not have totally eliminated the problem but would have helped. There are several products labeled for this purpose and, if applied properly, would not enter the soil and would have no influence on other plants.

In both cases, however, the trees have been removed for some time and the downward movement of material within the trunk (translocation) has ceased. It is too late to use the chemicals on the stump.

Chemical control is still possible by applying a properly diluted herbicide labeled for control of "broadleaf" weeds or a non-selective herbicide that will kill all vegetation to which it is applied. In your situation, your trees have become broadleaf weeds. There are many appropriate products, so check with your local nursery and read the labels before purchasing. Your local Cooperative Extension Service agent can help you make a product selection appropriate for the purpose and for your area. Remember that these products will damage desirable plants if applied improperly. Products containing 2,4-D can be absorbed by the roots of other desirable plants. Products containing glyphosate cannot be absorbed from the soil but can harm other plants if applied on a windy day. There are also other products you may use. Check with your local Cooperative Extension agent about the longevity in the soil of any product you consider using if you plan to replant where the chemical will be applied.

You will probably find that a single chemical application will not be sufficient. The root system has a lot of stored food reserves that may be used to produce new sprouts. The chemical will kill the new sprouts, but other sprouts will form. Over time, you can deplete the stored food reserves and the sprouts will stop forming.

In addition to chemical application or in place of chemicals, you may apply some old-fashioned elbow grease and remove the sprouts by digging them up or mowing them. Digging them up a few inches below the ground level will be sufficient and better than just mowing. You will not need to dig several feet down - just cut below the soil line. In either case (using chemicals or mechanical removal), the object is to deplete the stored food reserves in the roots system by removing new growth after it draws upon the stored food but before it begins to return food to the roots.

Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, email: desertblooms@nmsu.edu, office: 505-865-7340, ext. 113.

For more gardening information, visit the NMSU Extension Horticulture page at Desert Blooms and the NMSU Horticulture Publications page.

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