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Pruning Techniques

Our Vegetation Management Program uses approved arboricultural tree pruning practices to maintain tree health while establishing a clearance between power lines and tree branches. This technique was developed by the Tree Care Industry Association, approved by the American National Standard Institute (ANSI), adopted by the arboriculture industry as its standard, and endorsed by the Arbor Day Foundation and the International Society of Arboriculture.

On property maintained by the customer or land owner, we trim trees adjacent to conductors using a technique called directional pruning. Each limb removed using this technique is removed either where it joins another limb or at the tree’s trunk. This method promotes proper wound closure. Each cut is made just outside the branch collar, so as not to leave a stub or create a larger than necessary wound. 

While these cuts are not always aesthetically pleasing, our pruning practices are based on sound arboricultural principles and are the best techniques to provide reliable service and maintain the health of the tree. Our pruning practices are focused on improving system reliability and preserving the health of the trees along our rights of ways.  

Duke Energy strictly adheres to the industry safety standards contained in the American National Standards Institute (ANSI) Z133-2017 requirements. These specifications are considered the standard for Duke Energy’s transmission and distribution systems, which are aligned with the industry-accepted tree pruning standards as prescribed in the ANSI A-300 Part 1 -2017 Pruning Standard (tree, shrub and other woody plant management standard practices).

Duke Energy has ISA certified arborists on staff to ensure proper pruning practices are adhered to by all hired Vegetation Management professionals.

Examples of tree trimming methods
Illustration of proper limb removal
To avoid the stripping of bark during limb removal, the following cuts are made: an undercut (A) is made a foot or so from the limb junction. The limb is now “stub cut” (B,C). The final “lateral cut” is made (D,E). Note that if the final cut was made straight down from point (D), it results in a much larger “opening” than necessary. However, by making the angled cut (D to E), the diameter of the cut was minimized, the “branch collar” was not disturbed and no “stub” was left. 

When only a portion of a limb is to be removed, the portion removed should be cut back to an adjoining limb the size of which is at least one-third the diameter of the portion removed whenever possible.

Illustration of directional pruning method