Ice

Tree structure has evolved to support heavy loads at great heights, but there is a limit to the weight capacity of branches that are periodically tested by snow and ice. Tension and/or compression wood develops during the course of a tree’s lifetime at points in the stem and branches where bending occurs most frequently and to the greatest degree. In general, hardwoods tend to react to bending by forming more tension wood, whereas conifers produce more compression wood. Unusually severe snow or ice events can exceed the capacity of compression / tension wood, but more commonly, branch or stem breakage occurs at weak points such as branch unions, old injuries, decay pockets, or in branches with included bark. Branches that have developed from epicormic sprouts (suckers) are weakly attached to the stem and are often the first to fail under heavy loads. When possible, proper stocking and pruning will minimize the risk of limb or stem breakage. Stands that have been recently thinned may be more severely damaged, especially if trees have been suppressed for an extended period of time.