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Large pruning cuts can lead to internal decay

old pruning cutOld pruning cuts on numerous tree species can result in unseen decay inside the trunk and main branches. Large cuts more than about 6 inches in diameter can become entry points for fungi that begin the decay process.

The 8-inch diameter pruning cut shown in the right photo was made about 23 years ago 50 feet from the ground. The 70 mph winds broke the tree at the weak point created by the decay from the old pruning cut.

Note that despite the extensive discoloration and decay inside, the cut had completely closed over and decay could not be seen from the outside of the tree.

decayed branch