In our last blog post, we discussed the parts of a tree. In this blog post, we’ll take a look at the parts of a tree’s trunk (yes, there’s more than just the bark!). Halo Tree Service offers the best tree services in Troy. From stump removal to tree trimming, we can help with all of your tree needs. Continue reading, and then call us for your next tree service job!


The Trunk

The trunk of a tree is the support structure. It holds the tree up, and it supports all of the tree, from the leaves and branches to the heart of the tree. There are four inner layers of a tree, which has the primary job to deliver nutrients up and down through a system of tubes. Below, we’ll examine more of this process.

Xylem or Sapwood

The xylem, or sapwood, are the most recently added layers of a tree and are closer to the bark. The cells in the xylem layer transport water and nutrients to and fro from the roots all the way to the crown of the tree. As the tree grows, the inner xylem cells die, forming the tree’s heartwood.


Heartwood is the older xylem cells that have since died. Its job is to support the tree. Halo Tree Service in Troy notes that you can recognize heartwood by its darker color. It is full of stored sugars, dyes, and oils.

Phloem or Inner bark

The phloem layer of the tree is the closest to the center of the tree. Known sometimes as the inner bark, this layer of the tree carries the sap of the tree (which is basically just glorified sugar water along with nutrients) from the leaves down to the rest of the tree. The phloem is sandwiched between the cambium and the outer bark.


The cambium is the tissue and cell supplier of the trees. It’s the thinnest inner tree layer and the tree cells that it produces can become a part of any of the other layers. The cambium also adds a new layer to the xylem of the trunk, which results in the growth rings you see every year that helps you know how old the tree is. The cambium is what thickens the trunk, branches, and roots.


While not an inner layer of the tree, the bark is the outermost layer of the tree’s trunk. Bark covers the entire tree’s trunk, branches, and twigs and is akin to human skin. Its main purpose is to protect the trees soft and precious inner layers for the environment, harsh temperature changes, insects, diseases, and storms. Halo Tree Service in Troy notes that the bark is, in essence, dead phloem cells that have been pushed outward.


Trees, like all living creatures, need periodic maintenance in order to grow and be healthy. By investing in tree trimming, tree removal, and tree pruning services by Halo Tree Service, you will be helping to prolong the life of your trees and keep them enjoyable for years to come. Call us if you’re in the Troy area for the best tree services today!