Garden Help: What peeling bark on a tree means

So often we choose a tree because of its flowers, leaves, fall color or its fruit. Often, we forget about the bark. However, on many trees, the bark is the most interesting part of the tree. This can be especially true on deciduous trees that lose their leaves in the winter. The bark can be a feature that adds tremendous interest to a tree.

What exactly is bark and what does it do? Bark is a layer of dead cells made up of compressed phloem and cork. The bark is like the armor of the tree. It protects the tree from being injured by animals, insects or disease. To do this the bark of some trees have thorns, while others actually contain chemicals that taste bad to insects. Bark also insulates the cambium from heat and cold. The thick bark of pine trees protects all important cambium from fire.

The layer of tissue under the bark is called the phloem. This tissue distributes the carbohydrates made in the leaves throughout the tree. Without bark protecting the phloem tissue, the tree would starve and the wood of the tree would dry out. Bark also needs to be a little elastic. As a tree grows in diameter, the bark needs to grow along with it.

People have used bark for many different products. Bark was used to make baskets, some clothing and as a covering for canoes. Today, bark is still used in many things. Bottle corks are made from the bark of the cork oak. Cinnamon comes from the bark of the Cinnamomum verum tree. Bark is even used in the formation of several medicinal products, including some promising cancer treatments. The original source for aspirin was from the bark of willow trees.

So, is peeling or loose bark bad? The answer depends on what is under the peeling bark. If the loose bark reveals “wood,” then the tree has been wounded to the extent that the bark is no longer attached to the tree. If the wound is small, the natural defenses of the tree takes over in a process called compartmentalization.

The tree tries to create a chemical barrier to stop any decay from going further into the wood while the tree forms “woundwood,” or “callous” that forms over the wound, sealing it closed. If the wound is extensive, such as the case of a vehicle hitting a tree, then only time will tell. The treatment would be to remove all the loose bark in a process called bark tracing. Do not remove bark that is tightly attached. There is no need to apply any wound sealant such as tar or pruning paint. These products actually interfere with the wound closure process.

If there is more bark under the loose bark, then the tree is fine. In this case, the loose bark indicates that the tree is growing larger in circumference. As it grows larger, the old bark splits, revealing the newly formed new bark underneath.

There are many trees that have interesting bark that is loose or peeling. Some of the more common trees in our area with peeling bark include river birch, lacebark elm, crape myrtle, sycamore and bald cypress. When you want to add some additional interest to your landscape consider using trees that have unusual or interesting bark.

Larry Figart is an urban forestry extension agent from the University of Florida/IFAS.