TERNARY PRUNING METHOD
The Ternary Pruning Method
Improper pruning could result in a larger wound and bark damage caused from the weight of the pruned limb stripping the bark of the branch collar and stem as it detaches. Literally, it peels off the stem’s bark, like skin off a banana, as the limb falls!
One pruning method to minimize this risk is the TERNARY PRUNING METHOD (TPM)* (or Ternary Method, for short) which is a 3-step process involving 3 specific pruning cuts.
Large limb removal in three steps for wound reduction (a.k.a. avoid bark stripping, etc.):
- Undercut (“Safety Cut”)
- Weight reduction cut
- Final (“Finishing”) cut
Step ONE: The first cut is an undercut no more than 1/3 the branch width. This is a safety cut to minimize the chances of stripping the bark of the branch collar and trunk underneath from the weight of the limb during the pruning process (particularly, Step TWO).
Step TWO: The second cut is on the upper surface a few inches ahead of the first cut. When properly executed, the branch will detach without stripping the bark because of the safety cut.
Step THREE: With the bulk of the weight of the branch removed, this final cut is just ahead of the branch bark ridge and branch collar.
The resulting cut will offer the tree a better chance of callusing over and sealing the wound, forming a knot, over a shorter period of time. This natural process is an important way a tree protects itself from invading insects, disease, and decay. Therefore, proper pruning techniques, like TPM, are essential.
The photo below is of a pear tree that was properly pruned a few years ago and the pruning wound was able to successfully callus over and form a knot.
Illustrations and photographs by Jeff Harris © 2015 Arbor Rangers, LLC
*Formerly (and sometimes still) referred to as the “double cut” method. The new name, Ternary Pruning Method got its name back in 2015. Early that year, Lindsey Purcell planned to write a publication featuring the latest best practices in tree pruning. He had already done his homework by consulting with field experts on the subject and spending many exhaustive months conducting additional research through countless university and trade publications. On February 14, he mentioned the project to Jeff Harris and asked his interest in helping with some illustrations, particularly concerning the “double cut” method on branches. Later that spring (May 4) he sent Jeff an image depicting an illustration he had found presenting the double cut method, but Lindsey desired a fresher perspective and asked Jeff for ideas. In subsequent conversations they discussed the irony of the name, which seemed particularly a little misleading because it actually involves three cuts, not just two, as the “double cut” name appeared to imply. It had been their experience to encounter inexperienced individuals, who sometimes would forget to make the final (third) cut, which often left a studded limb behind. By June 3, Jeff had produced a set of illustrations and suggested a more accurate name for the pruning method: “Ternary Pruning Method” (because it is a THREE-step limb removal procedure). That name made sense to Lindsey and he used it when he produced his new publication on the latest pruning practices, available as a free PDF download from the Purdue Education Store: FNR-506-W Tree Pruning Essentials (July 2015) and has been using it in his presentations ever since.