Why Do Branches Fall?

Hazards from branches are often overlooked until a tree branch comes crashing down on the house or the car. Do you know how to spot a hazard tree on your property? Are your trees ready to weather the winter storms?

The main reason branches fail is weak unions between the branch and the trunk.

Weak Unions:

Strong branch unions have upturned branch bark ridges at branch junctions. Annual rings of wood from the branch grow together with annual rings of wood from the stem, creating a sound, strong union all the way into the center of the tree.

A weak branch union occurs when a branch and grow so closely together that bark grows between them, inside the tree. The term for bark growing inside the tree is “included bark.” As more and more bark is included inside the tree, the weak union is formed that is more likely to fail under stress. If a weak union is cracked, cankered or decayed, the union is likely to fail, causing the branch to fall off the tree.

In storm damage surveys conducted by the University of Minnesota ’s Forest Resources Department, 21% of all landscape trees that failed in windstorms failed at weak branch unions. Some species are notorious are: European mountain ash, green ash, hackberry, boxelder, willow, red maple, silver maple, Amur maple, cherry and littleleaf linden.

Cagwin & Dorward’s ISA Certified Arborists can inspect your trees looking for any weak unions or Epicormic Branches to protect your trees and minimize your liability.

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