13 Parts of a Tree: Trunk Anatomy & Cambium Layers Explained (Tree Diagram)

Teacher explaining to a student in a classroom the parts of a tree: diagram, trunk anatomy, cambium layers of a tree and other layers of a tree as well as the life cycle of a tree to answer the question, how does a tree grow?

Have you ever wondered about the parts of a tree, trunk anatomy and the cambium layers and what they do?

Trees are a lovely, complex and crucial part of the world’s ecosystem.

Basic grade school education explains that the trunk, roots and leaves are the most commonly identified parts of a a tree, but there are some additional cool things about the trunk anatomy and cambium layers that you may not know.

This complete guide uses diagrams and other images to explore the parts of a tree, for anyone who is curious to learn more.

Tree Anatomy: Parts of a Tree Diagram

According to Thomas Crowther and Henry Glick, both imminent scientists from Yale, there are about 3.04 trillion trees on the planet.

These range from ground creepers to skyscrapers, varying in size, color, and types of fruits and what colorful flowers they grow annually.

Related Reading: How Many Trees Are in the World?

Despite their differences, from simply being deciduous, like Dogwood tree leaves and Birch tree leaves, or evergreen trees like conifers, all trees do have some basic parts in common.

The woody stems and trunk are just the beginning:

  1. Trunk: The most recognizable part of the tree and its support structure.
  2. Roots: Provide stability, water, and a food retrieval service, healthy roots are crucial for a tree’s survival.1
  3. Canopy: This is the collective name for the twigs, branches, and leaves on a tree
  4. Leaf: Essential for converting CO2 and sunlight into oxygen.
  5. Branch: Supports and helps to transport food to leaves, flowers, and fruits.
  6. Flowers: Apart from being attractive and fragrant, the pollen in flowers attracts pollinators so the tree can reproduce in other areas.
  7. Fruits: Similar to flowers, the fruits of a tree are there to attract animals and foragers to disperse the seeds wide and far. (Some trees do not produce fruit with seeds, but this is rare.)
  8. Bark: Affords protection for the tree against damage and is a barrier to pests.
  9. Taproot: Its primary function is to anchor the sapling or young tree into the ground and provide stability as it grows.
  10. Stems (Twigs): They are an extension of the branch to further carry food to the leaves and fruits as well as supply additional support.
  11. Limb: The first extension from the central trunk.
  12. Bole: This is part of the tree from the ground up to where the first limb sprouts.
  13. Cambium: Responsible for rejuvenating the bark and the wood of the tree.

The parts of a tree that are unknown are the ones that are generally underground or hidden from sight.

Graphics of parts of a tree with labels showing the leaves, crown (canopy), trunk, and roots.

Cambium, for example. Most people haven’t considered it, but it’s a crucial component that contributes to the health and well-being of a tree.

Cambium Layer of a Tree (Layers of a Tree): Parts of Tree Trunk

The trunk or bole of a tree is not just one solid pole of wood wrapped in thick bark. It has 6 layers and each one plays its role in the life cycle of the tree.

Outer Bark

  1. It acts like a shield to protect against physical damage.
  2. It protects against heat by conserving moisture within.
  3. It insulates the tree against cold weather that would damage the cells and heavy rain that would overwhelm the tree with too much water.
  4. And it wards off a certain amount of invasive insects and pests.

Inner Bark

This lining just beneath the bark is what transports nutrients to other parts of a tree and is known as the “phloem”. It soon becomes part of the outer bark, thickening it as the tree matures for added protection.2

Third Layer: Cambium Cell

The task of this layer is the rejuvenation of the trunk. Every year it grows new bark and new wood as well as boosts new cell growth to maintain the health and longevity of the tree.

Sapwood (Xylem): Fourth Layer

Sap and water are funneled through this thick layer of wood to the leaves and all parts of the tree.

The Fifth Layer: Core, Called the Heartwood

An extra strong fibrous pillar that supports the entire tree.

Pith: Center Point

Situated in the exact center of the trunk, the pith is like the main artery of the tree carrying essential nutrients from the deepest part of the rots to the uppermost branch.

Tree Growing Stages (How Does a Tree Grow and the Stages of a Tree Growing)

A tree, like any other living organism, has a beginning and an end. Depending on favorable environmental conditions, invasive pests, and diseases, that lifecycle can be anywhere from 10 to 300 years.

The first stage of life begins with a seed, dispersed by insects, birds, animals, or a stiff breeze.

Germination will occur as the seed sprouts and burrows into the earth, its roots spreading far and wide, and deeper in the search for nutrients and in the process establishing a solid foundation.

An image illustrating the process of seed germination, showing the development of a plant from a seed.

At the same time, the seedling emerges and continues to grow into a young sapling with leaves and branches emerging to capture whatever sunlight beams down.

The next phase will see the sapling develop into a mature tree that will then undergo an annual reproduction of flowers, fruits, leaves, and more seeds to start the lifecycle of a new tree.

The final stage of life is decline as the tree ceases production of fruits, becomes more prone to disease, and it eventually keels over. Decomposition ensues in all parts of the tree at a slow pace as nature reabsorbs its last bit of nutrients back into the earth.

At the end of its lifespan, it starts to decay and provide sustenance for insects and animals, finally becoming part of the surrounding ecosystem from whence it originally came.3

Life Cycle of a Tree

Some trees start producing fruit within 40 years and continue to do so for a further 60-100 years. When a tree has come to the end of its productive life and is displaying open signs of deterioration, it doesn’t necessarily mean that its usefulness is at an end, or even that it will suddenly topple over.

A tree can be dead, as in cease to grow and produce any new leaves, fruits, or flowers, and still be held erect by its trunk and root system. In this state, it can remain among other trees as deadwood for decades, unnoticeable as being any different until further decline overruns it.

Yet throughout this period, it can still be an important part of the local ecosystem, providing shelter for small animals and insects, as well as a source of food for birds and mammals who utilize all parts of a tree so that nothing will go to waste.

Parts of a Tree for Preschoolers

Trees are an important part of the world’s ecological system and an integral part of its biodiversity.

Children are just as aware as adults that climate change is happening and that greenhouse gases pose a threat to the quality of air that we breathe.4

The sooner they can comprehend that trees are pivotal to the climate, the better, and the quicker they can learn about the different parts of a tree, the faster they will appreciate the role that trees play in the future of the planet.

For them, just basic knowledge of a tree is sufficient so that they can identify what the trunk does, how the roots support the tree, what the crown (canopy) is, how leaves use sunlight, and what role the branches and twigs play in the tree’s health and survival.

How To Tell How Old a Tree Is Using Parts of a Tree

A technique first used by archeologists Andrew Ellicott Douglass and Clark Wissler in the early 1900s called dendrochronology is a scientific method that calculates a tree’s age by measuring the rings formed inside the trunk.5

These can only be seen only after the tree has been cut down, however, so the distance between them and the number of rings can be counted to reveal the tree’s age. The more rings per centimeter, the older the tree is.

Top shot of cut tree trunk showing the tree rings which help how to tell how old a tree is.

(Image: MableAmber6)

But, conversely, if there are no rings visible at all, then the tree would be classed as ancient, with possibly no way to accurately gauge its true age. An alternative method on how to tell how old a tree is that does not include felling an otherwise healthy tree is to use an online tree calculator tool or the length of the string.

  • Wrap a length of string around the trunk at a height of about 5 feet, marking where the two ends meet.
  • Measure the distance from the mark on the string to the end.
  • Divide that number by 2.5 to get the tree’s age.

Known as Mitchell’s rule, after the English botanist and dendrologist, Alan F. Mitchel, it estimates that the average tree will grow at a rate of 2.5 cm a year. Dividing the circumference of the trunk by this figure will determine the age of the tree.

So if the trunk of the tree measures 60 cm that would be divided by 2.5 to give an approximate age of 24 years. This method is not 100% accurate as it will vary by tree type, the growing conditions the tree has been in, and even the thickness of the bark.

If the types of trees are known then achieving a more accurate reading is possible. Here are 10 trees with just that piece of information to demonstrate the possible discrepancies in regard to tree type.

The more growth rate information available about the tree, the more precise the results, and the International Society of Arboriculture employs this system to gauge the health and age of a tree.7

Type of TreeDiameterGrowth Rate Per YearAge of Tree
1. Dogwood80 cm7.011.4 years old
2. Shingle Oak80 cm6.013.3 years old
3. Colorado Blue Spruce80 cm4.517.8 years old

Shingle Oak tree growth chart showing a line graph with Shingle Oak tree age on the x-axis and Shingle Oak tree height on the y-axis.

Type of TreeDiameterGrowth Rate Per YearAge of Tree
4. Scotch Pine80 cm3.522.86 years old
5. White Fir80 cm7.510.67 years old
6. White Ash80 cm5.016 years old

Scotch Pine tree growth chart showing fully grown Scotch Pine tree  in a line graph with Scotch Pine tree age on the x-axis and Scotch Pine tree height on the y-axis.

Type of TreeDiameterGrowth Rate Per YearAge of Tree
7. Red Maple80 cm4.517.8 years old
8. Cottonwood80 cm2.040 years old
9. Horsechestnut80 cm8.010 years old
10. Tulip80 cm3.026.67 years old

Red Maple tree growth chart showing full grown Red Maple tree in a line graph with Red Maple tree age on the x-axis and Red Maple tree height on the y-axis.

How To Tell the Height of a Tree

The most accurate method of measuring the height of a tree is to physically measure it from the base of the trunk to the tip of the canopy.8 But that’s not always practical or feasible if the tree stretches into the air as far as the eye can see.

There are, fortunately, a few tricks that will get the job done quickly and fairly accurately. Kids like the first one the most.

Method No. 1

Walk away from the tree and, still with your back turned towards it, bend over and look back between your legs. If the top of the tree cannot be seen, keep walking and bending over until parts of the tree are in view.

Place a stick or stone in that position and measure the distance between it and the base of the tree. That measurement will be a rough estimate of the height of the tree.

Method No. 2

Timing is the secret to this method, as is knowing your own height.

Use a yardstick to measure your own height for use as a baseline.

And then on a sunny day, and on a flat piece of land near the tree, measure your shadow until it matches your height, and then measure the shadow cast by the tree.

Method No. 3

Another fun one for kids involves a simple stick, a keen eye, and a tape measure.

The stick needs to be the same length as the outstretched arm holding it upright at a 90-degree angle.9

Graphics for The Stick Trick used to measure the height of a tree.

(Image: The Franklin Institute9)

Walking backward, stop when the top tip of the stick lines up with the top of the tree.10 Place the stick at your feet and measure the distance back to the base of the trunk to reveal the height of the tree.

Thanks to the Pythagorean theorem, this way to measure a height of a tree is both simple and fun!

What Are Some of the Negative Consequences of Tree Cutting?

Deforestation has an incredibly adverse effect on the climate when conducted without controls. By removing established forests, it drastically reduces the amount of carbon dioxide removed from the atmosphere and the production of oxygen.

However, there are some responsible ways to harvest trees, replacing them so that the planet doesn’t suffer.

Unfortunately, cutting down trees to make way for agricultural crops and cattle farming has devastated entire forests, displaced villagers, and changed entire communities for the worst.

Widespread tree removal can cause soil erosion, eliminate the habitats of local animals, and even alter the water retention capabilities of the atmosphere. This can result in droughts that were never encountered before or water shortages that reduce crop production and food availability.

Even parts of a tree on healthy tree that remains in the vicinity will be affected as the nutrients available for their roots are depleted, which will create a knock-on effect as the tree becomes destabilized.

Unless a form of regeneration is employed where more new trees are planted than those cut-down, the negative consequences will only worsen.

Do Tree Stumps Regrow?

Nature always finds a way to produce life. If a tree is cut down but the stump and all the roots are left in place, the roots will sprout new shoots, and eventually, a new tree will grow in its stead.

This regrowth will depend on the conditions of the soil and water availability, as well as the health of the tree before it was felled.

The Willow tree is known to be particularly hardy and resilient, and the root system will aggressively seek out more nutrients to survive and reproduce, possibly to the detriment of nearby fauna and flora.

Tree stump situated on dirt with grass in the background.

(Image: Fapro111)

It is important to remember that there are different types of roots that grow from the stump of a tree aside from the main central taproot.

  • Lateral Roots- These provide additional stability as they grow outwards as far as necessary to anchor the tree firmly in place, often breaking the surface of the soil.
  • Sinker Roots- Their purpose is to force their way several feet deeper underground in search of any surrounding water and nutrients that are not near the surface.12
  • Oblique Roots- Any available space left is filled by these roots as they branch out in search of minerals and any other sources of water.
  • Fine Roots- A beneficial fungus called Mycorrhizae assist these finer roots to absorb minute traces of nutrients in the soil that the tree would otherwise be unable to utilize.

The root system of a tree is a bit more complex than it at first appears and will fight for its continued survival. If considering hiring a tree service to completely cut down rather than simply prune parts of a tree, then eliminating the roots should definitely be factored into the quotation.

How Many Leaves on a Tree?

How many leaves on a tree? This is an interesting question that will vary considerably by the species of tree, its age, its habitat, weather conditions, and even the season. Physically counting the leaves on the crown of a tree in full bloom is not only daunting but impractical.

Imagine if halfway through the process after a couple of hours of counting studiously, a gentle breeze dislodges dozens of leaves. Fortunately, measuring the size of the canopy and multiplying this figure by 4 will help.

Roughly calculate how many leaves occupy an area of a square foot in the foliage and multiply that by the size of the canopy.

What Can You Make Out of a Tree Trunk?

Rather than discard all parts of a tree that has been cut down or fallen over in your backyard, you should consider ways that the wood can be used despite a few wounds or cavities to make other items that can either be for the garden itself or for indoor use.13

Pile of logs cut from tree trunks.

(Image: 559837514)

Uses that the still-viable wood can be put to are

  • Making stools or table tops by cutting the trunk into sections, cleaning them up, and either varnishing or painting them for weather-proofing.
  • Carve the trunk into a bench and use an exterior sealant for protection.
  • Sculpt faces or figurines into the stump.
  • Cut the trunk into discs and use them as a stepping-stone feature.
  • Create an indoor coffee table after cleaning and varnishing it to a shine.
  • With a few well-placed holes, a slim tree trunk can make an interesting wine rack.

There are a variety of items that can be fashioned from a tree trunk that is still partially in the ground or completely cut down and uprooted.

With a bit of ingenuity and creativity, the tree that has just been cut down can have a second lease of life given a bit of thought.

Remember, as long as the wood isn’t burned, it will continue to hold in the emissions it sequestered while it was living.

Amazing Facts About Trees You Probably Don’t Know

There can be no denying that trees are amazing. They are awe-inspiring in the sheer heights that they can grow to as well as their enormous trunks, yet there are still so much we don’t know about them.

Here are just 5 amazing things you may not know about trees:

  1. Trees as we know them haven’t been around all that long. Even though there are over 3 trillion trees on earth and the planet is 4.5 billion years old, it has only been in the last 420 million years that trees have sprung up as they have.
  2. The leaves of trees can actually lower the ambient temperature by evaporating water on their surfaces.
  3. Some trees live forever – barring illness and natural catastrophes – such as the Methuselah which has been alive for over 5,000 years.
  4. Trees communicate by a fungus in the soil called Mycorrhizal that not only provides nutrients through the roots but acts as a conduit to share these nutrients and minerals throughout the entire forest. This method of underground societal communication among trees was first discovered by Suzanne Simard in 1997 when she wrote about it in her Ph.D. thesis.
  5. Scientists have discovered that all parts of a tree release a substance called phytoncides that, basically, promote a feeling of happiness in forests when spending time surrounded by the serenity of nature.15

In fact, forest bathing is very popular in Japan where walkers enjoy long treks in the woods to relieve anxiety and even reduce blood pressure.

Any city that has hundreds of trees strategically planted in congested urban areas is helping to keep its citizens healthy. Not only do trees emit oxygen but they also remove harmful air pollutants that every year aggravate asthma sufferers and those with breathing difficulties.

They should be appreciated for the positive impact they have on the quality of our lives and the numerous benefits derived from all the parts of a tree that make up this incredible plant.

Frequently Asked Questions About Parts of a Tree

Is a Tree a Plant?

Yes, essentially a tree is a big plant supported by a wooden trunk with other wooden appendages growing from all parts of a tree.

Do Trees Produce Oxygen?

Trees produce oxygen by photosynthesis.16 This occurs from the absorption of the sun’s rays and carbon dioxide which undergoes a chemical reaction that turns them into oxygen for the tree to release into the atmosphere.

How Much Oxygen Do Trees Produce?

An average tree on a yearly basis can emit 250 pounds of oxygen back into the air.

How Much Carbon Does a Tree Capture? How Much CO2 Does a Tree Absorb?

For those wondering, how much carbon does a tree capture or how much CO2 does a tree absorb, in general, about 48 pounds of carbon dioxide can be absorbed by an average-sized mature tree, but each species has its own amount, some trees sequester more carbon than others.

What Is It Called Where the Branch Meets the Trunk?

This meeting point is called the branch union.


1Fairfax County Virginia. (2023). Understanding Tree Roots. Fairfax County Virginia. Retrieved February 23, 2023, from <https://www.fairfaxcounty.gov/soil-water-conservation/understanding-tree-roots>

2University of Florida. (2020, January 24). Tree biology. Landscape Plants. Retrieved February 23, 2023, from <https://hort.ifas.ufl.edu/woody/compartments-phloem.shtml>

3Loehle, C. (1988). Lifespans of Common Trees in Virginia. Virginia BIG Trees. Retrieved February 23, 2023, from <https://bigtree.cnre.vt.edu/lifespan.html>

4Butcher, K., & Pletcher, J. (2017, April 24). Gardening with young children helps their development. MSU Extension. Retrieved February 23, 2023, from <https://www.canr.msu.edu/news/gardening_with_young_children_helps_their_development>

5National Park Service. (2022, June 3). Dendrochronology. National Park Service. Retrieved February 23, 2023, from <https://www.nps.gov/tont/learn/nature/dendrochronology.htm>

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8Newport City Council. (2023). Measuring Trees. Newport City Council. Retrieved February 23, 2023, from <https://www.newport.gov.uk/documents/Leisure-and-Tourism/Countryside/Measuring-Trees.pdf>

9THE FRANKLIN INSTITUTE. (2023). Tall Trees. THE FRANKLIN INSTITUTE. Retrieved February 23, 2023, from <https://www.fi.edu/en/science-recipes/tall-trees>

10Mass.gov. (2023). How to Measure Trees. Mass.gov. Retrieved February 23, 2023, from <https://www.mass.gov/how-to/how-to-measure-trees>

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12Austin Blog. (2018, January 26). How Tree Roots Work Part II: Digging Deeper. austintexas.gov. Retrieved February 23, 2023, from <https://www.austintexas.gov/blog/how-tree-roots-work-part-ii-digging-deeper>

13University of Florida. (2020, January 24). Hollows and cavities. Landscape Plants. Retrieved February 23, 2023, from <https://hort.ifas.ufl.edu/woody/cavity.shtml>

145598375. Pixabay, Retrieved February 23, 2023, from <https://pixabay.com/photos/wood-wooden-saw-background-nature-3163292/>

15Forest Service U.S. Department of Agriculture. (2019, August 22). Walk in the woods for wellness: Health benefits of forests. Forest Service U.S. Department of Agriculture. Retrieved February 23, 2023, from <https://www.fs.usda.gov/inside-fs/out-and-about/walk-woods-wellness-health-benefits-forests>

16Understanding Global Change. (2023). Photosynthesis. Understanding Global Change. Retrieved February 23, 2023, from <https://ugc.berkeley.edu/background-content/photosynthesis/>