One risk of tree breakage is the presence of one or more dominant stems. Codominant stems that grow horizontally through one another to crisscross, or “v-crotch” generally weaken the structural integrity of a branch. This is due, in part, to the lack of trunk-to-stem anchoring tissues and the presence of bark between stems. When the angle between two adjacent sides of the v-crotch is greater than 180 degrees, there is a higher risk of structural failure. One way to avoid the problems associated with codominant stems is planting trees that have a single leader.
Removing a codominant stem removes the need for additional pruning and/or stemming, allows for a single branching structure. Other methods to bolster a declining tree are by either cabling or bracing the weak area with cables or wrapping in wire.
Another common condition that can cause structural problems is an overextended limb. A condition that can often result in structural problems is the presence of long and/or heavy limbs. These are limbs that grow longer than they should, typically extending in a horizontal or downward direction. The foliage is located on the end of the long branch. Breakage often occurs at the junction where the tree’s branch joins its trunk. In some cases, the branch may bend due to tension and compression forces. These failures usually occur when the branches are subject to heavy loads such as wind, snow or ice.
Given the size of some trees, large cuts to limbs may be avoided by installing cables that help direct wood growth. Corrective pruning is a course of action that can be taken early in order to prevent the overhanging branch from rubbing against other branches.
A third structural problem is weakly anchored trees. Poorly anchored trees are often a result of improper transplanting or insufficient planting. Pruning of the branch, installation of supports, or combined techniques may be recommended.