Tree bark provides far more than mere external protection, serving as a shield for the tree’s inner, living tissues. Beneath the rough outer layer lies the phloem, a vascular system responsible for transporting sugars, the tree’s food supply, down from the leaves to the roots. Just inside the phloem is the cambium, a thin layer of actively dividing cells that creates new phloem on the outside and new xylem, or sapwood, on the inside. Stripping the bark interrupts this delicate vascular flow, which can be a life-threatening injury that requires immediate attention to prevent the tree from starving or becoming vulnerable to infection.
Assessing the Severity of Bark Damage
Accurately determining the extent of the damage, particularly to the vascular cambium layer, is the first step. A superficial scrape that removes only the outer, dead bark (rhytidome) is a minor injury the tree can usually overcome. Damage is more severe if it penetrates the cambium layer and exposes the sapwood beneath.
The most severe form of damage is known as girdling, which occurs when a strip of bark is removed around the entire circumference of the trunk. Complete girdling effectively severs the phloem, blocking the downward movement of sugars to the roots, which will eventually cause the root system to starve. A tree can often survive if the damage affects less than 25% of the trunk’s circumference, but wounds approaching or exceeding 50% significantly decrease the chances of recovery.
Immediate First Aid for the Tree Wound
If the injury is partial, immediate first aid can significantly improve the tree’s prognosis. The primary goal is to encourage the formation of callus tissue, the tree’s natural defense mechanism to seal off the injury. Begin by carefully cleaning the wound site, removing any loose bark fragments, wood shavings, or debris.
Next, use a sharp, sterilized knife to perform bark tracing, trimming the ragged edges of the remaining bark. Cut the torn bark back to healthy, firmly attached tissue in the shape of an elongated oval, ensuring the long axis runs vertically. This clean edge promotes the formation of wound wood, specialized cells that roll over the injury to seal it off.
Resist the urge to apply traditional wound sealants, such as tar or paint. These materials are detrimental, as they can trap moisture and create an environment favorable for fungal growth and decay. The wound should be left open to the air, allowing the tree to initiate its natural compartmentalization process. In some cases, a light, breathable covering, like burlap, may be temporarily secured to protect the exposed sapwood from sunscald or pests while allowing air circulation.
Long-Term Recovery and Monitoring
After the initial wound treatment, the long-term focus shifts to reducing stress and maximizing the tree’s natural healing capacity. The tree will expend significant energy creating new callus tissue, making supplemental water a crucial component of recovery care. Employ deep, infrequent watering, especially during dry periods, ensuring the soil remains consistently moist but not saturated.
Reducing competition from surrounding turf or weeds will also benefit the recovering tree. Applying a layer of organic mulch around the base helps retain soil moisture and regulate soil temperature. The mulch should be kept a few inches away from the trunk itself to prevent moisture from causing decay or creating habitat for rodents. High-nitrogen fertilizers should be avoided initially, as they can promote excessive canopy growth that diverts energy away from wound closure.
Successful healing is visually confirmed by the formation of wound wood, which appears as a raised, swollen ring of tissue growing inward from the perimeter of the injury. Monitor the tree monthly for signs of secondary stress or failure, such as sudden dieback of branches in the canopy or excessive, prolonged sap leakage from the wound. If the wound closure is slow or the tree shows signs of decline, inspect the area for signs of wood-boring insects, which are often attracted to stressed or wounded trees.
When to Call a Professional Arborist
While homeowners can manage minor or moderate bark damage, severe injuries require the specialized intervention of a certified arborist. The most compelling reason to call a professional is for damage that has completely girdled the tree, which is often fatal without advanced techniques. Girdling damage exceeding 50% of the trunk’s circumference generally falls into this category.
For severe girdling, an arborist may attempt a complex repair called bridge grafting to re-establish the severed vascular connection. This procedure involves using scions—dormant, detached twigs—to bridge the injured area. The arborist connects the cambium layer of the scions to the healthy bark above and below the girdle, restoring the flow of carbohydrates.
Bridge grafting requires specialized knowledge, precise timing in early spring when the bark is “slipping,” and proper technique to ensure the scions fuse with the trunk. An arborist should also be consulted if the damage is high on the trunk, involves large structural branches, or if the tree is a highly valued specimen. The professional can accurately assess the tree’s structural integrity and determine if advanced repair is justified.