What Are the Parts of a Tree and Their Functions?

You think you may know all the parts of a tree. Even if you can name every part, maybe you don’t know how each part interacts within the whole or their main functions. Our goal today is to make you a little more knowledgeable about the parts of a tree. It may not make you a certified arborist like our team members are, but it will certainly help you to recognize when your tree has a problem and when to give us a call. At the very least, you might have a deeper appreciation of how intricate a tree can be. Let’s start from the bottom of the tree.

Roots

Not only do roots absorb water and nutrients from the soil, but half of their job is to anchor the tree so it doesn’t fall over. When the roots are compromised, the tree is in big trouble. Not only will it be more difficult for the tree to receive nutrients and water; it may fall over. A tree’s roots also help the environment around it by stabilizing the soil and preventing erosion. You may be able to see some of these roots on the top of the ground before they dig down—this is only part of the root system. There are smaller, secondary “feeder” roots that extend beyond that. The roots are also where extra food is stored and saved up for lean times, such as in the winter or during a drought.

The taproot is the main root or roots that grow straight down. If you’re removing a tree or a stump, getting the taproot dug up is the main goal. Even if the tree doesn’t develop a taproot—such as in cases where the dirt is too tightly packed—the secondary root system can still be substantial and require specialized tools, equipment, and experience to dig up. Each root is also surrounded by tiny root hairs. Altogether, it can be an extensive network. In fact, trees can be linked underground, sharing resources and connections, like its own kind of nervous system.

Trunk or Bole

Bark

It may look like a telephone pole, but there’s a lot going on below the surface. There are several layers in the trunk. You’ll see the outer bark of the tree—it’s part of how the tree is classified. Bark can be as distinct as different animals. For instance, the bark of the madrone tree tends to fragment and peel off in curls, giving it a papery appearance. The bark of the cedar tree was used by Native Americans and cut off in long strips to be made into medicines, clothing, and baskets. The bark of a ponderosa pine smells like vanilla. In fact, the most outer bark of trees has a characteristic odor and look to it.

Center

The trunk is riddled with tiny tubes that run between the roots and the crown of the tree, pumping nutrients and water up into the leaves. The very center core of the trunk is called the heartwood and is the densest part of the tree. It must have a strong central structure to support the sapwood around it and the branches above it. It’s also the most protected part of the tree, so if you discover insects or other pests nesting in the heartwood of the tree, you know that the tree has been highly compromised. Usually, the heartwood is darker than the rest of the wood of the tree and contains stored sugar and oils.

Layers In-Between

The next layer is called the sapwood or xylem. The sapwood itself is alive, but over the years, the inner layers of sapwood die and create rings. This is why when you cut a cross-section of a felled tree, you can see how many growing seasons the tree has survived. Sometimes you can even see scars that the tree has experienced and healed and grown over, such as if the tree weathered a major cut or the loss of a main limb or lived through a forest fire.

Trees that live in areas prone to wildfires tend to have thicker bark, which protects the living sapwood. The ponderosa pine has adapted especially well to high-frequency, low-intensity fires by dropping lower branches as it grows taller, which prevents the fire from climbing high up on the tree.

Crown

The crown of the tree includes everything above the trunk: leaves or needles, flowers, twigs, and branches.

The first thick branches of a tree are usually called boughs. These are the branches sturdy enough that you could climb on them. The smaller branches—the ones you don’t want to be climbing on—are called twigs. These have clusters of needles on them if your tree is an evergreen, or they have leaves fall every autumn. Collectively, the leaves are called foliage.

The needles and leaves of a tree are important for food production in a tree. This is where the tree combines energy from sunlight, carbon dioxide from the air, and water to form sugars and oxygen. This process is called photosynthesis.

Leaves and needles also filter the air of particles and create oxygen. Humans and animals exhale carbon dioxide and inhale oxygen. In the height of the summer, leaves are as important to a tree as a hat is to you. Instead of getting sunburned, the leaves take the brunt of the sunlight and cool the tree through the loss of water by evaporation. This is why it’s important for you to water your trees more in the summertime.

If your tree is a fruit tree, it will also sprout flowers in the spring. When the flowers are pollinated, you will see your tree bear fruit that usually will be ripe in the autumn. These fruits contain seeds that will later sprout into a new plant.

At Mr. Tree, we aim to help you keep all the parts of your trees healthy and happy. We’ve served the Portland metro area and surrounding communities since 2000 and are licensed, bonded, and insured for your protection. Contact us today if you have questions about anything from maintenance, pruning, removal, and beyond.