the parts of a tree and their functions

The Parts of a Tree and Their Functions

Everybody remembers learning about trees and plants at school in science class, however, how much of it do we remember? Sure, you can likely point out and name most parts of a tree, but how much do you know about each part and the role it plays within the whole tree itself?

In this article, we’re going to delve a little deeper into the anatomy of a tree. Perhaps you won’t quite be ready to become a qualified arborist by the end of this article, but it will certainly help you to better understand the trees on your property and perhaps even identify when your tree may be suffering a particular ailment.

The Roots

As you may know, the roots of a tree are the tendrils that keep a tree anchored into the earth, but they play a bigger role than that as well. The roots of a tree are also designed to absorb nutrients and water through the soil.

If in the event the roots of a tree become damaged or compromised it can spell disaster for a tree. Not only will a tree struggle to get all of the nutrients and water that it needs, but it may topple over in the wind!

Further to that, the roots of a tree can help the environment by stabilising the soil and helping to prevent further erosion.

When you look at a large tree you’ll notice a few larger roots above the surface before they dig beyond into the dirt. This is the beginning of the root system. Following that, they branch off into smaller “feeder” roots that extend far below.

The main root of a tree that grows straight down beneath the tree is known as the taproot. If ever you find yourself in a position where you need to remove a tree at its stump, digging the taproot out of the earth will be the primary objective – this, however, isn’t something that we would recommend attempting without the proper experience or stump grinding equipment.

Finally, each root has tiny “root hairs” which can help with the gathering of water and nutrients. Another interesting fact about a tree’s roots is that they can be linked underground with other trees, sharing resources and connections. Some people believe that trees use these nervous systems to communicate with and support one another, just as a family might.

The Trunk (or Bole)

Next up we have the trunk (or bole) of the tree. This is the central wooden axis of the tree and is most typically brown. The trunk contains a central network of smaller tubes that run deep into the roots and the leaves – essentially serves as a kind of “plumbing” system in the plant, not so dissimilar to the way our veins and arteries work.

The trunk of a tree is divided into some inner layers:

  • Outer bark: Outer bark is (as the name suggests) the outermost layer of a tree’s trunk, branches, and twigs. The bark on various trees and plants can have different and unique characteristics such as specific odours and scents. The function of the bark of a tree is to act as a protective layer for the delicate inner tree.
  • Cambium: The cambium of a tree is the thin layer of living tissue. This consists of active, growing cells that are present just underneath the surface of the outer bark. Each season a tree will add a new layer to its trunk which then produces visible annual growth rings in most trees that can be used to determine a tree’s age. The function of the cambium is to produce new cells and allow the tree to grow in diameter.
  • Sapwood: The sapwood (aka xylem) of a tree are the youngest layers of wood that are made up of a living network of cells. As the years pass by the inner layers of a tree’s sapwood die. The function of sapwood is not only to help support the crown of the tree but also to give it its shape.
  • Heartwood: The heartwood of a tree is the dead sapwood and xylem cells that are found closer to the centre of the trunk itself. These are often filled with stored sugars, dyes, and oils. The function is simply to store helpful biochemicals as a long-term solution.
  • Pith: The pith of a tree is the thin dark spot that is present at the very centre of a tree trunk and acts as a pipeline for the water and minerals from the roots up through to the leaves in the crown of the tree.
  • Inner bark (or phloem): The inner bark of a tree is another pipeline of sorts located between the outer bark and the cambium of a tree and is designed to transport the energy and food absorbed by the leaves through to the rest of the tree.


The Crown

The crown of a tree is everything that lives above the trunk of a tree, i.e., the branches, twigs, flowers, and leaves.

  • Leaves: The leaves of a tree are attached at the crown and are designed to not only absorb sunlight to produce food and energy for the tree but to prevent the inner layers of the tree from scorching from too much exposure to sunlight. Additionally, leaves help to filter dust and other particles from the atmosphere creating cleaner air. They also help to keep the tree itself cool through the loss of water by evaporation. The collective term of the leaves on a tree is “foliage”.
  • Branches: The branches on a tree are the first limbs that stem from the central wooden trunk. Branches function by providing the tree with strength and support, including a storage area for food materials in the form of sugar which are required to help the plant grow and promote a healthy metabolism.
  • Twigs: The twigs are the smaller limbs that stem off from the larger branches (or boughs), giving rise to new plants and leaves.
  • Flowers: The flowers of a tree tend to be the most colourful and attractive part. These tend to remain attached to the terminal branches and later help with the development of fruit.
  • Fruit: The fruit is the edible part of a tree that develops from the flowers and contains a seed that can give rise to a new tree entirely – and so continues the cycle.



And there we have it: a round-about guide to a tree’s anatomy. Naturally, there are countless species of tree, each with its unique characteristics. However, on the whole, these parts are present on the majority of trees.

We hope that you have found this article interesting and that you’ve enjoyed learning more about the various parts of a tree and how they function.


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