What is included bark?

Included bark forms when two branches or a branch and trunk grow side by side at a narrow angle, causing the bark to be wedged between them instead of being shed naturally. The branch collar, which is the tree's biological mechanism for healing wounds and compartmentalizing decay, cannot develop properly when bark remains trapped in the union. This prevents the formation of strong wood and leaves the attachment point vulnerable.

The weakness at an included bark junction makes the branch more likely to split or crack under wind, ice load, or the weight of foliage. Over time, water penetrates the bark and decaying wood accumulates at the union, further reducing the structural integrity of the limb. A narrow union angle combined with included bark creates especially high failure risk, particularly in species like silver maples and willows that are prone to weak branching.

Professional arborists inspect branch structure for included bark during tree risk assessments, especially on older trees or those near buildings and power lines. Branches with included bark cannot be strengthened by cabling or bracing alone. Certified arborists may recommend removal of the affected limb to reduce the hazard, or monitoring if the risk to nearby property is low. Proper pruning practices during a tree's early years can prevent included bark from forming in the first place.