Just like an onion, there are many layers to a tree’s bark. The 5 main layers are the outer bark, inner bark (phloem), cambium cell layer, sapwood, and heartwood. The outer bark is the tree’s first line of defense from rain, extreme temperatures, and insects. It is always renewed by the inner bark, which is a pipeline through which food passes through. The inner bark only lives for a short time and eventually becomes part of the outer bark. Next, is the cambium cell layer or just the cambium. The cambium is the layer of the tree that grows and is softer than the rest of the tree. Thanks to the cambium, the tree is able to grow taller and larger! Then, it is sapwood. Sapwood is the tree’s main pipeline for moving water and nutrients. Then, the last and strongest layer, heartwood. Heartwood is the very center of the tree and holds the tree up so that it does not topple over. It is the central, support pillar of the tree. Those are the 5 layers of a tree!
Check out this diagram below to see the layers of a tree!