Trees depend on bark to protect the inside of the trunk. Damage to the bark is more than an eyesore; it can be a life-or-death issue for your landscape trees.
Bark Damage Problems
Bark damage can lead to tree death, so it is not a minor problem. The bark serves an important purpose -- it protects the inner wood from insect and disease incursion. If the bark is missing, insects can more easily burrow into the wood. Disease pathogens, mainly fungal but also bacterial and viral, can also more easily gain access to the vascular system and heartwood of the tree. These issues can turn deadly for the tree, and there isn't always a cure.
Another issue with bark damage is a condition called girdling. Girdling occurs when there is missing bark around the entire circumference of the tree. This causes a break in the vascular system, which means the tree no longer moves water and nutrients between roots and leaves. The result is that the tree dies off above the girdled section. There is no way to save a girdled tree.
Causes of Bark Damage
Lawnmowers and string trimmers are the main causes of bark damage, as both can knock off or tear the bark if they come in contact with the tree when you are mowing the lawn close to the trunk. Animals, like deer and squirrels, may also eat the bark off of trees, particularly in late winter or early spring when other food sources are scarce.
Girdling damage that isn't a result of animal feeding is likely caused by tying a narrow rope or chain around the trunk. The friction of the movement of the narrow cord will cause the bark to separate from the trunk if it doesn't cut into it completely.
Prevention and Treatment
Prevention is best since recovery from bark damage can't be guaranteed. Mulch around trees so there is no need to cut the grass or trim weeds right up against the trunk. If you tie ropes around a tree, such as for a clothesline or hammock, use wide nylon straps instead of narrow cords, and remove them as soon as you are done using them. Further, guard against animal damage in winter by wrapping trunks with burlap or placing a cage around the tree.
If bark damage does occur and the tree is not girdled, use a sharp knife to clean up the wound so that the edges of the bark are smooth. Smooth-edged wounds can be sealed by the tree more quickly, which prevents pest and disease incursion. If the tree is girdled, then removal is the safest option.
Contact a tree service if you have damaged bark on any of your landscape trees.