For all intents and purposes, tree bark is the skin of the tree. The main tree bark function is to protect the phloem layer. The phloem layer is like our own circulatory system. It brings the energy produced by the leaves to the rest of the tree. Because the tree bark function is to protect the layer that brings food, when tree bark is scratched or damaged, this tender phloem layer below is also damaged. If the tree bark damage goes less than 25 percent of the way around the tree, the tree will be fine and will survive without a problem, provided that the wound is treated and is not left open to disease. If the tree bark damage goes from 25 percent to 50 percent, the tree will suffer some damage but most likely will survive. Damage will appear in the form of lost leaves and dead branches. Wounds of this size need to be treated as soon as possible and should be watched carefully. If the tree bark damage is greater than 50 percent, the life of the tree is at risk. If the tree is damaged around 100 percent of the tree, this is called girdling. It is very difficult to save a tree with this much damage and the tree will most likely die.

No matter how much of the tree bark has been damaged, you will need to repair the wound. If the tree is simply scratched, wash the wound out with plain soap and water to help reduce the amount of pathogens that may be in the scratch and that could cause further damage. Wash the wound thoroughly with plain water after this. Allow the scratch to heal in the open air. Do not use a sealant.

Jagged wounds will interfere with the tree’s ability to transport nutrients so you will need to clean cut the wound. You do this by removing tree bark by cutting an oval around the circumference of the damage. The top and bottom of the wound there will be for the points of the oval. Do this as shallowly and as close to the wound as possible. Let the wound air heal. Do not use sealant. Instead, the tree will seal wounds with a "callus" tissue. The tree produces new wood to grow around the wound. This isolates and protects the wound from further exposure and damage.

Conclusion. Healthy trees usually recover from wounding quickly. Try to keep wounded trees growing vigorously by watering them during droughts and providing proper fertilization. This will increase the rate of wound closure, enhance callus growth and improve the resistance to decay mechanisms.

Hope this helps!

Tree wounds. For some inexplicable reason, some people are compelled to “manage” a process that plants have evolved over millions of years. Every year, trees form hundreds of tiny abscission layers as leaves senesce and fall. Wounds left from branch breakage are callused over and compartmentalized. It’s important to recognize that trees do not heal. Instead, they isolate damage through formation of suberized, lignified wood that physically and chemically repels invasion. Callus develops at the edge of the wound and gradually expands towards the center. This wound wood remains for the life of the tree; bark does not regenerate itself the same way our skin does. It may be justifiable to use a fungicide or insecticide during spring or summer. Finally, the use of wound dressing “for aesthetic reasons” is never justified. For damaged bark, if the bark is still on the tree, use a tree wrap to hold it in place while the tree repairs itself. If the damage has left an open wound, trim off any jagged edges and let the tree close off the area naturally. The best way to help a tree recover from being wounded is to ensure proper fertilization, watering, and mulching methods. Remember, trees do not heal wounds the way other living organisms do, they seal them. Since trees cannot replace damaged tissue, they have developed a clever way of dealing with potentially life-threatening wounds. Through a process called compartmentalization, a tree seals off damaged or diseased areas by forming walls around it, literally encasing it, allowing the tree to grow around it and flourish.