Planting trees from containers

Causes of circling roots
Preventing circling roots
Treating circling roots

Pot bound (also called root bound) root balls from containers have large or many roots on the outer edge of the ball. It is best not to plant trees in this condition because roots could girdle the trunk as the tree grows. The tree could also become unstable later because few supporting roots grow from the outside curved portion of a root.

If you must plant a tree with circling roots, these roots should be cut aggressively with a shovel, knife or pruning tool (click lower left photo) to prevent them from girdling the tree later, especially if they are near the top of the root ball. Make three or four slices an inch or two deep from the top of the root ball to the bottom. If in doubt about whether a root is large enough to cut, go ahead and cut it. Tear the outside of the root ball off if you wish. This will be best for the tree in the long run.

Research shows that if there is a shoot growth reduction from root pruning container grown trees at planting, the effect is negligible (Dana and Blessing 1994). Other work shows a reduction in shoot growth following root slicing only if plants are under irrigated (Gilman et al. 1996)

Recent studies show that slicing the root ball from top to bottom in several locations does not increase root growth after planting (Gilman et al. 1996; Dana and Blessing 1994).

However, it does appear to enhance distribution of regenerated roots in the backfill soil profile. Instead of growing almost exclusively from the bottom of the root ball, slicing encouraged root regeneration along the slices from the top to the bottom of the ball. This could help establish the plant quicker by allowing the roots to quickly explore a larger volume of backfill soil.

Be sure to remove any synthetic material such as fabric or plastics that might be wrapped around the root ball. Some of these are designed to reduce root circling in the nursery but should be removed before installing the tree in the landscape.