Bark is the outermost layer of trees and other woody plants. It serves to protect the living tissues of the plant. Cutting the bark can damage these tissues. If damage is extensive, it may kill the tree.
Anatomy of a Tree
The interior of trees consists of several layers, each with an important purpose. Tree growth occurs on the outside of the trunk. The innermost core of the trunk is the oldest wood. The outermost area, just under the bark, is the cambium, which generates new wood. If you look at a cut section of a tree trunk, you will see the dark interior wood, called the heart wood. This is dead tissue, and serves to support the tree. Around that is a lighter colored layer called sapwood. Sapwood is living tissue, carrying water and nutrients from the roots up to the leaves. At the outside edge of the sapwood is the cambium, the growing tissue. Wrapped around the outside is the bark, which helps protect the living tissue of the cambium and sapwood from damage by weather, insects or blows.
Cutting the bark on a tree will often damage the living sapwood underneath. If the cut is small, or does not extend far, the tree can often survive the injury, though it may be at risk of infection from insects or fungus. If it is not further infected, over time the small injury may grow closed. However, if the bark is cut in large areas, or around much of the trunk perimeter, the damage can prevent nutrients and water being carried upwards, and the tree may die.
Protecting Trees in your Yard or Garden
The most common causes of major bark damage in the yard or garden are collisions with lawnmowers, weed-whackers or cars. To prevent lawnmower damage, encircle the base of each tree with mulch or ground-covering plants such as ivy, so that you do not have to mow or weed-whack close to the trunk. To prevent car damage, place trees carefully in the landscape, away from driveways and road edges, or surround them with reflectors to help guide drivers. Deer and livestock can damage trees by chewing or rubbing against the bark. Young trees, which have thin bark, are particularly prone to damage. If this is a problem, use appropriate fencing or repellents to keep animals away from the trunks of important trees.
Repairing Bark Damage
Minor cuts or scrapes will usually grow closed without further problems. Care should be taken to provide the tree with sufficient water and nutrients after injury, to help it heal more quickly. Damage covering more than half of the perimeter of the trunk will usually cause the tree to die. In the case of larger injuries, trimming the rough edges of the damaged area will aid in the tree healing itself. Use a sharp knife to gently trim the loosened bark away, leaving a simple oval or round area. Do not cut too deeply, only enough to remove the ragged bark. Applying sealants is not recommended. If parts of the tree begin to die, prune those parts away. If the tree fails to recover, it may need to be removed.
Exceptions to the Rule
There are some species of tree which are well-adapted to having bark removed without harm to the tree. The most well-known is the cork tree, a variety of oak native to the Mediterranean. Cork is the thick bark of this species, which is harvested by removing large sections every nine to 12 years. The bark grows back, allowing repeated harvests at long intervals.
tree injury, lawnmower damage, tree bark