Girdling roots are roots that encircle the trunk or other roots of a tree and choke off the flow of water and nutrients. This can lead to stress, dieback, and ultimately the death of the tree.
These roots can often be traced back to improper planting technique. Simple planting mistakes may not manifest as problematic girdling roots for many years, however, and by that point it may be too late to correct the damage. That’s why early detection of girdling roots is vital. A trunk that doesn’t flare out near the ground is a good indicator that a tree may be dealing with girdling roots just beneath the surface. If the tree looks like a telephone pole entering the ground, gentle excavation around the base of the trunk may reveal potential problems.
If a small girdling root is still developing, it may be an opportunity to cut it away and prevent it from causing long-term damage. That said, large girdling roots should not be removed in all cases, as it may cause significant damage to the tree and impact its ability to anchor itself to the soil.
To avoid girdling roots when planting trees:
To correct existing girdling roots:
- Cut away, loosen, or straighten circling roots, especially if planting a containerized or balled and burlapped tree
- Dig a wide planting hole at least three times the size of the root system. Scrape or scratch into the sides of the planting hole to loosen the soil and prevent a “glazing” effect, which may eventually deflect roots
- Ensure that the tree is planted at the proper depth—the root flare must be visible even after the ground has settled
- Do not apply more than three inches of mulch and ensure that it is not piled directly against the trunk. “Volcano mulching” is a common and harmful mistake that can lead to girdling roots and other issues.
- Remove excessive soil or mulch so that the root flare is exposed
- If a girdling root is found and it is two inches in diameter or less, use a small saw or a mallet and chisel to cut away several inches of the girdling root where it makes contact with the trunk
- If a girdling root that is larger or has grafted with the trunk is found, removal is not always the best option. Residents struggling with large girdling roots should contact an arborist for advice specific to their trees’ needs.