Tree bark serves as the primary defense, protecting inner layers from external threats like insects, disease, and physical injury. The bark shields the phloem, which transports sugars from the leaves down to the roots. Just beneath the phloem lies the vascular cambium, a thin layer of cells that produces new bark and wood, increasing the trunk’s girth. Deer cause damage by rubbing their antlers, typically in the fall, stripping this protective bark and severing the phloem layer, creating an urgent threat to the tree’s survival.
Immediate Care and Preparing the Wound
For minor to moderate injuries that do not completely encircle the trunk, the tree can often recover through its natural healing process. Immediate care aims to help the tree efficiently seal off the damaged area and prevent decay from spreading into the healthy wood. The first step, called bark tracing, involves using a sharp, disinfected knife to carefully trim away any loose or ragged bark from the edges of the wound.
This trimming should create a smooth, clean edge, ideally in an elliptical shape, which encourages the formation of callus tissue. The wound should then be left exposed to the air, as applying commercial wound dressings, paints, or tars is counterproductive. These substances trap moisture, which delays natural healing and can encourage fungal or bacterial growth.
The tree’s defense mechanism, known as Compartmentalization of Decay in Trees (CODIT), involves forming barriers to isolate the injury. New callus tissue grows from the healthy cambium around the wound edges, gradually rolling inward over the exposed wood. The success of this healing depends on the percentage of circumference damage; trees with less than 25% damage have a high probability of survival and recovery.
Specialized Repair for Severe Girdling
Damage that encircles the entire trunk, known as girdling, is a severe injury that severs the phloem, interrupting the flow of sugars to the roots. A completely girdled tree will likely die because its root system starves without nutrients. The specialized technique to save such a tree is called bridge grafting, which artificially re-establishes the connection between the tissues above and below the wound.
Bridge grafting is best performed in the early spring, just as the tree is breaking dormancy and the bark begins to “slip.” This technique requires dormant, pencil-sized twigs, known as scions, to span the damaged area. The scions are cut slightly longer than the wound to allow for a slight bow when inserted, ensuring better contact.
The procedure involves preparing the wound edges and cutting small flaps into the healthy bark both above and below the girdled section. The ends of the scions are cut to a wedge shape and inserted under these flaps, ensuring the cambium layers align perfectly. Scions must be placed with the original top end facing up, as placing them upside down prevents nutrient flow, and they should be spaced every three to four inches around the trunk.
Once secured with small tacking nails, the graft unions are sealed with grafting wax or a non-toxic compound to prevent drying. Bridge grafting requires precise alignment of the cambium layers to restore the vascular connection. Due to the complexity, severe girdling often warrants consultation with a certified arborist.
Essential Strategies for Future Protection
After treating existing damage, preventing future deer-related injury is essential for the tree’s long-term health. Proactive measures are necessary because deer often return to the same areas. Physical barriers are the most reliable method for deterring antler rubbing, which typically occurs from late summer through fall.
Individual Tree Protection
Individual tree protectors, such as plastic or wire mesh sleeves, should be installed around the trunks of young, susceptible trees. These protectors must be tall enough (four to five feet) to prevent rubbing and should be removed in the spring to avoid trapping moisture or harboring pests. For multiple trees, constructing a rigid wire-mesh cylinder or cage around the tree, well away from the trunk, is highly effective.
Property Fencing and Repellents
For comprehensive property protection, perimeter fencing is the ultimate defense, though it must be at least eight feet high to prevent deer from jumping. Repellent sprays, which use strong odors or tastes, can deter browsing on leaves and buds, but they are not effective against antler rubbing. Repellents must be reapplied frequently, especially following rain or snow, to maintain effectiveness throughout the deer activity season.