How to Kill Tree Roots
Tree roots sometimes don't know when to call it a day, producing new shoots long after the tree was removed. Taking down a tree sometimes increases the number of shoots that grow from its roots, and they can appear many feet from where the tree stood. When removing tree roots isn't possible because they spread too far or into inaccessible places, such as under a patio or shed, then pruning or using a systemic herbicide can provide the solution.
Removing Tree Roots
Removing tree roots is hard work but effective. In thick, hard, clay soil, tree roots may not extend very far. Removing tree roots in sandy loam soil is more difficult because the root system is often extensive and vigorous.
Push a garden fork 6 to 8 inches into the soil where the tree grew, and lever the fork upward. Pull up the tree roots that appear. Follow the roots as they spread outward, digging and pulling them up. Prune roots that grow too deeply to dig up.
After pruning tree roots, wipe pruning shear blades with a cloth that was dipped in rubbing alcohol to sterilize the blades.
Pruning the shoots that appear from tree roots eventually starves the roots when the pruning is done on a regular basis, but the process can take two or three growing seasons. Roots need the energy created by leaves on shoots to survive.
Every month through the growing season, prune new shoots as close to the ground as possible with pruning shears. Check for shoots growing away from the area where the tree stood, such as in garden borders and lawns, and prune them, too. Sterilize the pruning shears when you finish.
Spraying Roots with Herbicide
Systemic herbicide controls tree roots by traveling downward from the shoots. Glyphosate and triclopyr are two systemic herbicides that control tree roots. Because these herbicides also harm desired plants, don't spray them near plants you wish to keep.
Put on a long-sleeved shirt, long pants, socks, closed-toe shoes, a hat, safety goggles, a face mask and gloves, and dilute an herbicide that is 2 percent triclopyr and 18 percent glyphosate at a rate of 6 fluid ounces per 1 gallon of water. Spray shoots from tree roots with the solution on a dry, still day when the shoots' leaves are fully expanded, ensuring you cover all the leaves and stems with the solution.
Treating a Stump with Herbicide
Applying systemic herbicide to holes drilled in the tree's stump will control the roots. The living part of a stump is just inside the bark, and treating that area with herbicide allows the chemicals to travel to the roots.
Drill holes that are 1/2 inch deep and 1/4 inch wide just inside the bark along the stump's cut surface. Four or five holes, evenly spaced, is sufficient for a stump 1 foot in diameter. Put on protective clothing, and pour an undiluted herbicide that is 2 percent triclopyr and 18 percent glyphosate into the holes until the holes are full.
- University of Minnesota Extension: Removing Trees and Shrubs
- Arizona Cooperative Extension, Yavapai County: Killing Woody Plant Stumps
- New Mexico State University, Southwest Yard and Garden: Removing Large Tree Saplings Near Foundation and in Hedges
- New Mexico State University, Southwest Yard and Garden: Trees Removed but Sprouts Develop from Roots