Root Pruning Saves Trees!

I worked for Friends of the Urban Forest (FUF ) from 1999 to early 2008. During that time it was not uncommon for street trees to reach a certain age, 5 to 7 years, and then just blow over in the wind. The tree was too big and heavy to be supported by stakes, but the roots had never developed because of root defects, caused by nursery containers early in life. Every winter storm generated hundreds of calls for downed trees and many could not be saved. 

This root wrapping around the trunk began circling in a long-ago nursery container. If it is not removed soon, it will cause problems for the tree.

Around 2000 we began inspecting nursery stock and rejecting trees with really problematic roots. Around 2002 we began root pruning 18-month and 3 year trees at maintenance visits to correct circling roots found within the top few inches. In late 2007, we began extensive root pruning at planting as recommended by Dr. Ed Gilman and Brian Kempf. 


4 years later, this recent article, written by my successor, notes how the new planting method has improved tree rooting and reduced emergency “downed tree” calls. The data is there, so inspect and root prune your young trees.  Who wants to lose their tree 5 years after planting?

Tree Care Chronicles

Root pruning saves trees

by Heather Ellison, Tree Care Manager

Rainy and windy days used to keep me busy taking calls about downed trees and dispatching volunteer Emergency Tree Care crews.  Today, such days cause far fewer problems.  We have Ed Gilman at the University of Florida to thank!

Arborists once thought that when planting container-grown trees, we should massage the root ball, pulling away the outer circling roots and removing the root mass on the bottom. Root defects such as circling or kinked roots deep in the root ball were largely left untouched. Over time the problem roots would fail to grow out—leaving the trees unstable and vulnerable in storms—or they would impair the flow of water and nutrients to the tree, weakening it and making it more susceptible to pests and diseases.

Professor Gilman and Brian Kempf, director of the Urban Tree Foundation, showed that when tree roots are pruned, aggressively if necessary, the trees usually establish much faster, are far more stable and produce more feeder roots than un-pruned trees.  We have increasingly embraced this practice, and now it is the rule rather than the exception.

The results have been astounding.  Our trees are often firmly rooted six months after planting, and our emergency calls for fallen trees have dropped dramatically. 

For more info about Professor Gilman and his research projects, visit http://bit.ly/edgilman.  For more info on container-grown trees and root establishment, see http://bit.ly/containertrees.