According to the Federal Emergency Management Agency (FEMA), a branch of the United States Department of Homeland Security, "three-fourths of the damage that trees incur during storms is predictable and preventable".
What Happens to Trees During a Storm?
Often the reaction of a tree to the wind dynamics of a storm has a direct correlation with the distribution of leaves on the tree as well as individual branches. Because there is more territory to catch the gust, wind forces tend to be more strenuous where the foliage is the heaviest.
Light rain and even small amounts of hard rain are helpful and necessary. Several hours or days of constant rain can loosen the soil around the tree and add weight to the branches and leaves causing a weak resistance to wind.
The pounding on the leaves and branches by hail can cause damage to elements of the leaves, branches and the trunk.
Pruning Do's and Don'ts
Proper pruning can do nothing but help the tree and its support system, while improper pruning can make your trees more vulnerable to the effects of the storm. Always prune the damaged or dead limbs, branches that cross or rub up against another branch, and branches that are scarcely attached at the trunk.
You want to reduce the area of resistance for the wind, but you must also remember that trees need leaves and branches for photosynthesis and protection. The ANSI A300 Pruning Standards (American National Standards Institute) recommends pruning no more than 25% of the foliage in a single growing season. Since restrained in the amount you should prune, it is perilous to be meticulous removing live branches and foliage from the entire tree including the outer third of the crown.
"Lion's Tailing" is a common mistake that can be disastrous. By thinning an excessive amount of lower branches, giving the tree a lion's tail shape, the tree becomes top-heavy and more capable of toppling over in heavy winds. It can also generate long-term problems such as sunburn of the trunk and reduce the tapering of the branches.
Cabling, Bracing and Propping Systems
If you notice a tree that seems ill-prepare for storm season, a propping system may be the solution. These man made devices are designed to support the weight of the tree or individual branches and create limits of mobility for the tree. Many larger trees can benefit from these techniques, but should only be considered when there is a reasonable assurance that it will reduce the risk of tree failure and all other options are insufficient.
Annually employ a tree care specialist to come and evaluate your trees professionally to ensure appropriate attention and repair to your trees.