porcupine damage on bark

(Question)

Hello; abt 2 wks ago a porcupine (I believe) tore the bark from the trunk of my ironwood tree; about 50% is girdled, and it’s abt 3 ft from the ground. The tree is abt 7″ dbh with a large crown. Grows in partial shade in nw Scarborough. Soil is mostly clay. It’s abt 14 yrs old. And I would really miss this tree. The only thing I’ve done is clean the edges of the wound with a sharp blade and put chicken wire around it to prevent further damage. Any assistance would be greatly appreciated! _P

(Answer)

This is a very serious problem, as you’ve identified. The reason that girdling is so dangerous is that the phloem layer of tissue just below the bark is responsible for carrying food produced in the leaves by photosynthesis to the roots. Without this food, the roots ultimately die and cease sending water and minerals to the leaves, after which the leaves die. We usually say that a tree is able to overcome girdling of about 25% of its circumference but the greater the damage beyond that, the greater the risk to the tree. There is a technique used to try to repair such damage: bridge grafting, which is an attempt to connect the layers above and below the damage to try to restore the movement of food. It is quite a complex procedure.  I am providing you with links to several sites that describe it:  New Mexico State University and one from the Ontario Ministry of Food, Agriculture and Rural Affairs. Since it is such a complex task, I would strongly recommend that you employ the services of a certified arborist. You can find one in your area by visiting the site of the International Society for Arboriculture or using their Find an Arborist feature. I wish you the best of luck in saving your ironwood tree!