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Pruning with an Undercut

April 07, 2014

Pruning small tree and shrub branches is easy with just one cut of hand pruners. But pruning thick branches is a bit more complicated to do properly and requires several steps, including making an undercut.

Pruning, as necessary as it is, leaves tree wounds that can become easy entry ways for diseases or pests to harm or even kill a tree, just like a human skin cut can become infected and cause greater harm. Leaving a nice straight and smooth cut after the pruning will help the tree wound heal more quickly and complete. The undercut is the first of three different cuts in a three step process to avoid the heavy weight of the falling branch from pulling and tearing off extra bark as it falls, leaving a rigged wound that will not heal properly.

First, make the undercut on the bottom side of the branch several inches away from where that branch joins the main trunk or branch, and cut upwards about 1/3rd of the way through the branch. Do not cut more than 1/3rd of the way through as this may cause the weight of the branch to pull it down to early.

Make the second cut just a couple inches up from the first cut, moving farther away from the main trunk. Start cutting on the top side of the branch and cut downward all the way through the branch until the branch breaks free. The undercut should have prevented any extra bark from being stripped and pulled away when the branch fell.

The third and final cut should be made just beyond the branch collar, which is the slightly swollen/ridged area you want to leave around the base of the branch where it joins the trunk. This cut can be made all the way through the branch at once because the stub that is left should not have much weight to it and so will not pull or strip away any extra bark off with it, leaving a nice straight and smooth cut.

-Jonathan Milbrodt, TBG Plant Records Curator

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