A girdling root is a root that circles around at least one side of the main trunk. You’ll usually see them at or slightly below the soil surface. These roots wrap tightly around the trunk, putting pressure on it. As result, movement of water and nutrients to the leaves is restricted.
What causes girdling roots?
Incorrect planting is a major problem. Roots take the path of least resistance in growth. Therefore, girdling roots are more common in situations when the planting hole has not been dug wide enough or when the soil is compacted. In order to to prevent their formation, dig the planting hole twice as wide as the root ball. This will help roots to grow out radially.
Another mistake is planting trees too deeply. When soil buries or covers the root flare, the roots begin growing upwards. As they grow toward the surface, the roots tend to encircle the trunk. When planting, be sure to first identify the root flare, where the topmost root emerges from the trunk. Then make sure that root flare is even with the surrounding soil level or slightly higher. Further, if you already have a tree in the ground and cannot see the root flare, remove excess soil or mulch for healthier growth.
Nursery practices may also cause girdling roots when a tree is planted with pot-bound, circling roots. A pot-bound root will continue to circle the trunk. Eventually, it will become a girdling root as the root grows. Several research trials have shown that breaking up pot-bound root balls before planting reduces formation.
Why are girdling roots bad?
A girdled trunk/stem weakens the tree. The tree will not live as long and will be more prone to disease and more likely to become infested with insects. Additionally, trees with girdling roots are more likely to be uprooted by wind.
What should be done if you find one?
As mentioned above, proper planting is critical to preventing circling roots. This should be the first line of defense! Even so, they are still incredibly common in yards and gardens.
Girdling roots should be removed carefully with a chisel or a saw. If there are multiple large girdling roots on a tree, it’s best to remove in several stages. In this way, existing roots can still be providing water and nutrients to the tree. Ultimately, removal will improve both the health and structure of the tree.