The bark contains the vascular system responsible for nutrient transport. Directly beneath the rough outer bark lies the phloem, a layer of living cells that carries sugars produced by the leaves downward to the roots. Damage that removes the bark and the phloem layer all the way around the trunk, known as girdling, effectively starves the root system. Quick action is necessary to re-establish this severed supply line for the tree’s survival.
Assessing the Severity of the Damage
The first step in recovery involves accurately determining the extent of the injury, as this dictates the proper treatment. Superficial scrapes that only remove the outer bark and leave the underlying tissues intact are minor and manageable. Damage that reaches the cambium layer, a thin, moist layer just inside the inner bark, is more serious because the cambium is responsible for all new growth of wood and bark.
The critical threshold for survival is based on the percentage of the trunk’s circumference that has been stripped. If less than 25% of the circumference is damaged, the tree has a high chance of recovery through its natural healing process, known as compartmentalization. Damage affecting 50% or more drastically reduces the likelihood of natural healing because the tree cannot effectively bridge the gap with callus tissue. A complete 100% girdle is often fatal unless immediate, specialized repair is performed to bypass the severed nutrient path.
Immediate Wound Care and Protection
After assessing the injury, the immediate goal is to clean the wound and encourage callus tissue formation. This process begins with bark tracing, using a sharp, sterilized knife to trim away any loose or torn bark around the edges of the wound. The cuts should be made cleanly back to healthy, firmly attached bark, shaping the wound into a smooth oval or elongated vertical shape. Rounded edges heal more efficiently than sharp, angular corners, providing the optimal starting point for new callus growth.
Do not apply wound paints, tars, or sealants to the exposed wood after trimming. Arboricultural consensus indicates these products do not promote healing and can trap moisture, creating an ideal environment for pathogens. The tree’s natural defense mechanism, compartmentalization of decay in trees (CODIT), is most effective when the wound is left exposed to air. If the injury occurred recently, the removed bark pieces can sometimes be placed back over the wound and secured with tape or burlap to protect the delicate cambium, but this practice is rarely successful unless done within hours.
Specialized Repair for Girdled Trees
For a tree that is more than 75% girdled, bridge grafting may be the only option to prevent death by starvation. This complex surgical technique creates a new vascular bridge to carry sugars past the damaged section. The repair involves using dormant shoots, known as scions, taken from the same tree or a compatible species. Scions are typically one-year-old growth, about a quarter to a half-inch in diameter, and are stored until the ideal grafting time in early spring.
The procedure is best performed when the tree’s sap is actively flowing, usually when the bark “slips” easily from the wood around the time buds begin to swell. The scions are cut several inches longer than the wound and sharpened into wedges at both ends. Small flaps of bark are carefully lifted above and below the damaged area. The scions are then inserted beneath these flaps, ensuring the cambium layers of the scion and the trunk align.
The scions are placed in a slight bow to allow for trunk movement and growth, then secured with small wire nails or brads. Multiple scions are placed every few inches around the trunk to ensure adequate transport capacity. The final step is sealing all cut areas and graft unions with specialized grafting wax or compound to prevent desiccation and infection. Consulting a certified arborist is often advisable for this advanced repair due to the technical precision required.
Long-Term Follow-up and Deterrents
Once immediate wound care or grafting is complete, focused long-term care supports the tree’s recovery. The wounded area must be monitored closely for signs of decay, insect infestation, or the successful formation of callus tissue or graft union. Callus tissue appears as a ridge of rolled bark growing from the edges of the wound toward the center, indicating the tree is sealing the injury. Supplemental care should focus on reducing environmental stress, particularly ensuring the tree receives adequate water during dry periods.
Avoid applying nitrogen-heavy fertilizers, as excessive top growth strains a compromised root system. The tree’s energy should be directed toward wound closure, not unnecessary foliage production. Preventing future damage requires physical barriers and repellents, especially during high-risk seasons like winter when animals seek food.
Physical Barriers and Repellents
Installing tree guards made of wire mesh or rigid plastic tubing around the trunk protects against rabbits, voles, and deer antler rubbing. Repellents containing ingredients like Thiram, which make the bark taste unpleasant, can be painted or sprayed onto the trunk. These repellents must be reapplied regularly, especially after rain or snow, for continued effectiveness.