How heavy is a 2-inch tree branch? Heavy enough to rip the protective bark from the tree trunk if it’s cut wrong, exposing the tree to harmful fungi, bacteria and insects that could eventually kill it.

Russell Bailey of Alexandria practices using a pruning saw.

About three dozen of the 42 people who are training to become Tree Stewards volunteers learned how to prevent that with what’s called the 3-cut method. First, they cut about halfway into the underside of the offending branch about a foot from the bark branch collar, where the branch attaches to the trunk. Then they cut the top of the branch clear through a few inches farther out, removing most of the weight of the branch and stopping the bark from tearing at the spot where they made the first cut. Finally, they sawed just outside the bark branch collar, where the tree is primed to grow protective wood over the pruning wound. They learned that no sealing material should be put on the fresh cut since the tree itself will cover the injury to prevent pathogens from entering.

Trainees learn to use pruning tools. Photos by Tree Steward Jo Allen

Trainees, accompanied by several Tree Stewards with pruning experience, practiced wielding pruning saws and bypass pruners to perform functional pruning on trees near Oakridge Elementary School in Arlington on Saturday, Jan. 11, as part of an Introduction to Pruning class taught by Hugh Robinson, who leads volunteer pruners in Arlington. His experienced group has pruned trees at all of Arlington’s public libraries, many of its 185 parks, and several of its public schools.

Training continues Sunday, when the group will learn structural pruning and practice it on young trees at Abingdon Elementary School in Arlington. A final pruning session will be held on Saturday, Feb. 8, in Douglas Park. Check out the course syllabus here.