Like it or not, winter brings the damaging effects of snow and ice to trees and shrubs. Wet snows are bad, but freezing rain is often worse. Ice storms typically start as warm rain falls through rapidly cooling air at ground-level. This results in rain quickly turning to ice on all exposed surfaces. Freezing rain is especially serious on evergreens and deciduous species that have not shed all their foliage.
Ice is heavy. A half inch on a power line can weigh 500 pounds. For trees this can amount to a weight increase of 30 times. Corrective pruning and replacement are the only solutions once breakage has occurred. But, are there options to prevent breakage?
The natural tendency is to protect plants by shaking the ice and snow from the branches. Unfortunately this can cause long-term damage. As ice bends the branches, fluids in conductive tissues are still liquid. Only later do they freeze. Shaking damages the conductive tubes and results in air pockets called embolisms or cavitation that will never again be able to conduct water and mineral elements. The result is that plants become stressed, grow poorly, suffer desiccation making them more likely to be attacked by diseases and insects.
The best recommendation for plants covered in wet snow or ice is to do nothing. If branches are in eminent danger of breaking, ice can be melted with cold water from a sprinkler. (Warm or hot water damages plants.) Using cold water to melt ice is with the understanding that both will refreeze on the ground. This should never be used where ice is likely to accumulate on walks or roads.