What Is Root Pruning: Learn About Root Pruning Trees And Shrubs

Pruning Of Tree Roots
root pruning
(Image credit: zoran simin)

What is root pruning? It is the process of cutting back long roots to encourage a tree or shrub to form new roots closer to the trunk (common in potted plants too). Tree root pruning is an essential step when you are transplanting an established tree or shrub. If you want to learn about root pruning, read on.

What is Root Pruning?

When you are transplanting established trees and shrubs, it’s best to move them from one location to another with as many roots as possible. The roots and soil that travel with the tree or shrub make up the root ball. Usually, a tree or bush planted in the ground will spread its roots far and wide. It would be impossible, in most cases, to try to include all of them in the plant’s root ball. Yet, gardeners know that the more roots that a tree has when it is transplanted, the faster and better it will adjust to its new location. Pruning tree roots before planting reduces transplant shock when the moving day comes. Root pruning trees and shrubs is a process intended to replace the lengthy roots with roots closer to the trunk that can be included in the root ball. Tree root pruning involves clipping the tree’s roots well about six months before the transplant. Pruning tree roots before planting gives the new roots time to grow. The best time to trim the roots of a tree or shrub to be transplanted depends on whether you are moving it in spring or in fall. Trees and shrubs destined for spring transplant should be root pruned in the autumn. Those to be transplanted in fall should be pruned in spring.

Root Pruning Trees and Shrubs

To begin root pruning, mark a circle on the soil around the tree or shrub to be transplanted. The size of the circle depends on the size of the tree and should also be the outer dimensions of the root ball. The bigger the tree, the bigger the circle. Once the circle is marked, tie up the lower branches of the tree or shrub with a cord to be sure they are not damaged in the process. Then dig a trench in the ground along the outside of the circle. As you dig, keep each strata of soil in a separate pile. Cut the roots you encounter with a sharp spade or shovel edge. When you have dug down sufficiently far to get the majority of the roots, fill the trench back in with the extracted soil. Replace it as it was, with the topsoil on top, then water well. When transplant day comes, you re-dig the trench and extricate the root ball. You will find that pruning tree roots before planting caused many new feeder roots to grow within the root ball.

Teo Spengler

Teo Spengler has been gardening for 30 years. She is a docent at the San Francisco Botanical Garden. Her passion is trees, 250 of which she has planted on her land in France.