Storm Damaged Trees
One of the most common but overlooked structural problems in trees is the development of codominant trunks. Codominant trunks involve two or more trunks of approximately equal diameter, growing closely together and joining at some point above the ground. This juncture is a point of structural weakness during storms, especially if decay is present.
The first image shows codominant stems of a large oak, with essentially nothing holding the two stems together. These stems can easily be pushed apart or twisted in strong winds or downdrafts; perhaps only slightly with everything returning to “normal” afterwards, or perhaps severely enough to result in tree failure. It should also be noted that as trunk circumference expands from year to year, the trunks continue to push against each other, and this tension increases the risk of failure.
The second image was submitted to our office following Hurricane Dorian. This flowering dogwood has two main trunks, with substantial decay visible on one of the stems. The top arrow indicates the general area of decay, while the two bottom arrows point out the extent of the split that occurred during the storm. This tree is in the process of falling apart, and no amount of tree paint can turn things around. However, in terms of potential hazards to people or structure, a dogwood is not a mature oak or pine tree. Selective pruning to reduce weight on the left side of the tree might buy time before that stem splits off completely at the crack.
For a comprehensive guide to evaluating storm damaged trees, hiring an arborist, tree selection and related issues, visit Storm Damaged Landscape Trees and be sure to bookmark it on your computer.