The Emerald Green Arborvitae (Thuja occidentalis ‘Emerald Green’) is a popular choice for privacy screens and landscape accents. However, white-tailed deer pose a significant threat to the health and shape of these evergreen trees. This article examines the plant’s palatability to deer and outlines practical steps for protection.
Understanding the Term Deer Resistant
The Emerald Green Arborvitae is generally a preferred food source for deer, meaning it is not truly deer resistant. In horticulture, the term “deer resistant” does not equate to “deer-proof.” It only suggests that a plant is less likely to be eaten compared to a highly palatable alternative. The Eastern Arborvitae species (Thuja occidentalis) is often rated by university extension programs as “occasionally to frequently severely damaged” by deer browsing. Deer are herbivores, and their preferences shift based on local availability, meaning any plant can become a target.
How to Identify Deer Damage
Identifying the culprit is the first step, as other pests or diseases can cause similar symptoms. Deer browsing leaves a characteristic signature because white-tailed deer lack upper incisor teeth. When feeding, they clamp down with their lower incisors and pull and tear the vegetation. This results in branches and twigs that have ragged, frayed, or torn ends, unlike the clean cuts left by rodents. Browsing damage typically occurs from ground level up to about six feet, the maximum vertical reach of a standing adult deer. Additionally, male deer (bucks) cause damage during the fall rutting season by rubbing their antlers against the trunks of young trees, stripping the bark in vertical shreds.
Environmental Factors Affecting Browsing
The failure of a plant’s natural resistance often comes down to local environmental conditions and deer density. Browsing pressure increases significantly during the winter months when snow cover limits access to other food sources. For deer, the evergreen foliage of arborvitae represents an accessible and relatively high-calorie food source during periods of scarcity. Areas with a high local deer population will inevitably experience greater browsing pressure, regardless of the plant species. Younger arborvitae with tender, newly established growth are often more palatable and susceptible than older, more mature specimens. The chemical defense mechanisms in plants, which can include secondary metabolites that are distasteful to deer, may be less concentrated in the newest growth, making it an easy target.
Effective Protection Methods
Since the Emerald Green Arborvitae is not reliably resistant, effective protection involves a combination of physical and chemical deterrents, especially during cold-weather months. The most reliable method is the use of physical barriers that prevent access entirely, such as temporary fencing or netting. To be effective, an exclusion fence should be at least eight feet high. For individual trees, wrapping the plants in burlap or mesh netting from late fall until early spring can physically block deer from reaching the foliage. Chemical repellents, which create an unpleasant taste or odor, should be applied strategically before browsing begins and reapplied consistently. Repellents lose efficacy after heavy rain or snow, necessitating reapplication every four to eight weeks, and rotating products prevents deer from becoming accustomed to a single deterrent.