Whatcom Tree Service knows all about trees: how to cultivate them, maintain them, and protect them from threats to their health. Our tree service enjoys sharing the knowledge we use to make it all possible. One often-overlooked aspect of our Western Washington trees is their bark. Did you know that bark contains the majority of living tissue in a tree’s stem and limbs, and is comprised of up to five layers? To help educate the tree owners from Geneva to Everson to Lynden, here is a general overview of tree bark.

Phellem, also known as cork, is the bark’s outer layer and contains tissue that is impervious to water and gas. The phellem is the tree’s first line of defense against weather, insects, and animals.

Phellogen is next layer in and contains a variety of cells that make growth possible for the plant. Typically only one cell layer thick, the phellogen also produces the tissues found in the phellem.

The phelloderm is interior to the phellogen, and is not present in all species of trees. For those that do have it, the phelloderm produces new outer layers during stem growth, and cells exterior to it die to become parts of the phellem and phellogen layers.

Interior to the phelloderm is the cortex, which is the most abundant material in stems and roots. The phloem comes next and is the most inner component of a tree’s bark.
Because bark contains the majority of a tree stem’s living cells, it is extremely important to protect it against any threats to its integrity. A cut in a tree’s bark is akin to a flesh wound in an animal; it is an injury that is potentially life-threatening. If you’re unsure as to whether your Geneva trees’ bark is healthy, contact our tree service today!