Repellents may be classified as either contact or area repellents. Contact repellents are applied directly to plants and repel by unpleasant taste for the animal. Area repellents are different in that they are applied in the vicinity of plants and usually repel by smell. Research studies show not every repellent works in every situation, but contact repellents are more effective than area repellents. For more reliable protection for shrubs and trees this winter, consider fencing or other barriers.
Initial costs are higher, but materials can usually be reused for several seasons.
Barriers could be put up as fences around shrub plantings or cylinders around individual plant trunks or stems. Poultry wire or hardware cloth is a good choice for material to use. Make the barrier high enough to protect the trunk or stem even when there is snow cover. While effective, barriers have the drawback of being unsightly when used in landscape settings. In areas with high populations of animals such as rabbits, this inconvenience may have to be tolerated to help assure the shrub or younger tree is protected from serious damage.