The bark serves as the first line of defense, protecting the delicate living tissues beneath from physical damage, insects, and disease. Directly beneath the bark is the phloem, which transports sugars (the tree’s food) down from the leaves to the roots. The cambium layer, situated between the phloem and the wood, produces new bark and new wood annually. Damage to this vascular system is serious because it can sever the flow of life-sustaining nutrients, but timely intervention can often save an injured tree.
Determining the Extent of Bark Damage
The probability of a tree’s survival depends on the severity and location of the bark damage, requiring a proper assessment. The most serious injury is girdling, where the bark is removed in a complete ring around the trunk. Since the phloem tissue is just under the bark, removing it entirely starves the root system, leading to the tree’s death.
A tree has a good chance of survival if the damage covers less than 25% of the trunk’s circumference. If the damage encircles between 25% and 50% of the trunk, the tree will require help to recover, though survival is still possible. Damage exceeding 50% significantly reduces the prognosis, as the tree’s natural healing process, known as compartmentalization, may be overwhelmed.
The depth of the injury is equally important. A superficial scrape that only removes the dead outer bark is less concerning than damage that penetrates the cambium layer. Common causes, such as scrapes from vehicle impacts, animal rubbing, or string trimmers, all pose a threat to the vascular layers. Recovery relies on the remaining cambium tissue bridging the wound to restore the severed connection.
Essential Steps for Immediate Wound Care
Once the wound is assessed, the immediate goal is to stabilize the area and encourage the tree’s natural defense mechanisms. The first step is bark tracing, which uses a sharp, clean tool to trim away any loose, ragged, or torn bark edges. These jagged pieces can prevent the formation of callus tissue, the tree’s equivalent of scar tissue.
The perimeter of the wound should be carefully shaped into a smooth oval, cutting only into the damaged tissue and avoiding healthy bark. This shaping provides the most favorable border for the tree to produce wound wood, which grows inward from the edges to close the gap. The exposed area should then be gently cleaned of any debris without scrubbing, which could further damage the underlying wood.
Current research advises against applying wound dressings or tree paint to seal the injury. Sealants do not prevent decay and can trap moisture, creating an environment for fungi and bacteria. Allowing the wound to remain open supports the tree’s natural compartmentalization process—its internal method of walling off injured tissue. An exception is in areas where specific, rapidly spreading diseases, such as oak wilt, are a concern; a specialized sealant may be applied there to prevent insect transmission.
Supportive Care for Tree Recovery
After immediate treatment, the tree’s long-term recovery depends on reducing environmental stress and maximizing its internal healing capacity. The tree needs energy reserves to form callus tissue and close the wound, making proper hydration important. Deep, consistent watering is necessary, especially during dry periods, to prevent drought stress during recovery.
Applying a 2 to 3 inch layer of organic mulch around the base is beneficial, as it helps retain soil moisture and stabilize soil temperature. Keep the mulch ring a few inches away from the trunk to prevent moisture buildup that could encourage rot near the wound site. This mulched area also creates a physical buffer, preventing future mechanical injuries from lawnmowers or string trimmers.
Avoid using heavy synthetic fertilizers immediately following an injury, as the tree’s energy should be directed toward wound closure, not excessive new leaf growth. An aggressive fertilization schedule can divert resources away from the defense process. The tree should be regularly monitored for signs of secondary issues, such as shelf fungi or pests, which indicate the tree’s defense system has been compromised.