Trees Facts

Trees [trēs]

Large perennial woody plants.


Big tree

Trees are the tallest of the plant life on the earth. They give us shade, wood, paper, food, medicine, and oxygen. They provide homes for many forms of wildlife. In some areas, they can even create weather. They are complex and abundant. They are also endangered. Let's find out more about trees…

Structure of a Tree

A tree is a plant; the trunk is the stem of the plant. The trunk is often covered in a heavy material known as bark which protects the trunk and gives it rigid support.

Tree Bark

Roots are the parts of the tree that usually grow under the ground and branch out to soak up and carry water to the trunk, the branches, and the leaves. Water is necessary to nourish the parts of a tree. Roots can grow deep into the soil and in some types of trees, they can branch out for great distances. In some types of trees, such as aspen, the roots can actually grow into additional trees even up to miles away. Some roots grow above ground — either to find water that is lacking below the ground or, in some species of trees because that is just where the roots of that kind of tree are normally found.

Tree roots

The leaves have a very special job of feeding the tree. Read on…



The leaves of the tree have a huge job in the life of a tree. Leaves perform a process known as photosynthesis. Photosynthesis creates food for the tree. During photosynthesis, the leaves take in carbon dioxide from the atmosphere. Then, using water that the roots have absorbed and energy from the sun, the leaves create a certain kind of sugar for the tree. This sugar acts as the tree's food. As part of this process, the tree releases oxygen which is used by people and animals when they breathe.


Carbon dioxide is actually poisonous to the air-breathing life on the earth. When we breathe out or exhale we get rid of carbon dioxide made by our bodies as a form of waste. This waste would build up over time and create a poisonous atmosphere for life on the earth. By using carbon dioxide during the photosynthesis process, trees and other plants reduce the amount of carbon dioxide in our atmosphere and makes the atmosphere safer for us. Trees rely on us for carbon dioxide and we rely on them for oxygen. A great system of working together, don't you think?

Learn more about the amazing process of photosynthesis on Science Trek's Botany page.

Photosynthesis Illustrated

Sunshine PLUS  

Chlorophyll and Carbon Dioxide  

PLUS Water

EQUALS = Sugar for the plant.

Diagram of photosynthesis
Diagram of photosynthesis

And the plant gives off oxygen.

Trees — A Natural Resource

Trees are important to the health of all of us. Because of photosynthesis, trees provide our world with oxygen. Other plants provide oxygen too, but because of their size, trees provide the largest amount of oxygen. Oxygen is crucial to our lives — without it, we could not survive.

Oxygen Producer

Trees provide additional resources to our environment. Trees also release moisture into the atmosphere. This is called transpiration. It is part of the water cycle and contributes to our weather. In the water cycle, moisture evaporates from plants, lakes, rivers, and other sources. This evaporated water drifts up into higher layers of our atmosphere where it condenses into water drops. These drops fall back to the earth in the form of rain, sleet, hail, or snow. This is called precipitation. In tropical rainforests, the transpiration can almost immediately be turned into precipitation. This creates a special condition in which it rains frequently as the water cycle is nearly non-stop right in that forest.

The Water Cycle

The sun causes water to evaporate or transpire from the plants.

This water creates clouds.

Water condenses and falls down on the plants as precipitation.

The plants soak up water from the ground through their root system.

Then, the water evaporates and returns to the clouds again.

A Natural Resource, Continued

Many animals rely on trees for homes, food, and protection. Some build homes inside the trees and others nest in the branches. Beavers cut whole trees down and build houses to live in from the fallen trees. Insects like to eat trees, seeds, and their leaves — so do many small animals like rabbits and birds. Even bigger animals such as deer and elk enjoy the bark and the leaves of certain trees.

Some plants actually call trees home too. Fungus such as mushrooms will often grow on the bark of trees. Moss is another plant that likes to hang around trees.

Fungus and moss on tree

Many animals are colored similar to trees' bark or leaves. This allows them a protection called camouflage. This way they can be safe from predators. Insects such as the katydid or the walking stick are good examples of this type of camouflage.

A lot of our food comes from trees. We harvest fruit such as apples, oranges, and bananas from trees. We also get maple syrup from maple trees for our pancakes. Certain nuts come from trees, such as walnuts and pecans.

Medicines are created with chemicals found in various tree species. Pain killers, cough syrup, medicines for high blood pressure, and for treating cancer are just a few of the many, many medications that science has produced with things found in tree leaves, bark, seeds, and fruit.

Photo of harvesting sap from a rubber tree
Harvesting sap from a rubber tree

Our daily lives are impacted by the things made from trees. Rubber comes from the rubber tree and can be made into tires, pencil erasers, balloons, rubber bands, and even rubber ducks.

Pencils, paper, rulers, furniture, cork bottle stoppers, bulletin boards, and even crayons come from wood products. Visit the Idaho Forests site to see a list of things made from wood.

Trees Help Our Environment

In addition to taking in carbon dioxide during photosynthesis, trees also clean other chemicals and pollutants from the air. Their leaves help to filter out particles and prevent us from breathing them into our lungs. They also filter water by soaking it in through their roots and then during transpiration they release clean water back into the environment. Their roots also help to prevent erosion, thereby keeping muddy water out of streams and rivers. Trees shade forests, parks, homes, playgrounds, and other areas which keeps temperatures lower. This lowered temperature keeps other plants and animals healthy. Trees can act as a windbreak and so they are often planted in rows along the edges of farms to help keep wind from destroying crops and drying out fields. Trees have been shown to reduce stress and improve the health of patients recovering from surgery.

Trees next to a thermal power plant
Trees next to a thermal power plant

Deciduous Trees

Trees come in two basic kinds: deciduous and coniferous. There are, however, a few species of trees which fall into both categories.

Deciduous trees have leaves that change color in the fall and drop off of the tree. The temperature changes that come about as the air gets colder in the fall, signal the tree to stop making chlorophyll. Chlorophyll is the chemical that makes leaves green. When the chlorophyll is gone, the leaves dry out and they change their color. Then the leaves die, fall off their branches, blow around, get raked up or, in time, can become part of the soil.

Maple tree

A deciduous tree creates seeds at certain times of the year. The seed is usually inside of the fruit — like an apple. The seeds can end up on the ground by way of animals, birds, and people or accidentally when, with a little help from gravity, the apple falls from the tree. When the seed grows, it will become another apple tree.

Apple Tree

Coniferous Trees

Coniferous trees, also called evergreen trees, stay green all year and usually have needles instead of leaves. The needles are often bunched into clusters of three or five. Pine trees, as they are sometimes referred to, are familiar as winter decorations because of their strong smell.

Evergreen Trees

Coniferous trees produce pine cones which contain seeds. The seeds are nestled into the cone very tightly and must wait for the cone to open up in order for the seeds to escape. Weather, temperature, moisture conditions, and time of year all play into a cone's ability to release its seeds. Some cones do not mature into releasing their seeds until years after the cone forms. Some are released during forest fires which helps the forest to rebuild after a fire.

Duglas Fir pinecones

Tree Rings

Trees grow a new layer or ring of bark every year. During good growing seasons, the tree will form a thick layer. In a season that may not have been good because of a lack of water or other challenges for the tree, the layer will be thin. For this reason, tree scientists will study a sample of a fallen tree's rings to track the history of the area in the years before. They can tell about weather, forest fires, droughts, floods, and other conditions that affected the trees and other life in the area.

Tree rings

Trees Are Endangered

In some parts of the world, trees are being removed in huge numbers. Whole forests are being cut down. This is called deforestation. The trees are being used for a variety of products, but they are not being replaced. The land is being cleared and homes and factories are being built in their place. Mining, cattle grazing, farms, and other industries are taking the place of the forests. When the trees are gone, they can no longer provide oxygen, clean air, shade, homes, food, or any of the other things that we have shared here. Erosion, increased carbon dioxide levels, increased temperatures, and increased pollution are just some of the consequences of removing the trees.


Forest fires also contribute to the deforestation problem. In areas of the United States and some other countries, trees are replanted following a forest fire. This helps, but it takes years and years for trees to reach the size of the trees that were lost.

What can we do to help trees?


Many communities offer free trees for planting. Plant a tree in your yard or on your school grounds. Make sure that the tree gets plenty of water. The deeper the water sinks into the soil, the deeper the roots will grow down. This will make the tree strong. Take care of the tree by avoiding games or activities near the tree that could damage it. Fence the tree off from small animals that might try to eat the bark. Stake the tree to help it to grow tall and healthy.

Photo of bark beetle on tree bark

Trees need help from humans to keep them healthy and continue growing. Sometimes trees must be cut down due to illness or overcrowding. This is also a protection for the other trees nearby and actually helps them to grow and thrive.

Watch for signs of insects or other things that could damage the tree. If you see evidence of insects eating the leaves or the bark, ask an adult to help you. There are medicines even for trees. Watch for damage to the bark — either by animal or accident. These wounds offer a place for insects to enter the tree easily. Insects that get inside a tree often do unseen damage that will eventually kill the tree. Tree experts, known as arborists, can provide protection for these damaged areas.

Recycle paper and other products that are made from trees. Reuse paper that has only been used on one side. Think twice before throwing paper products away. The fewer trees we need to cut down to make paper and wood products, the better.

What can you do to help? Plant trees, protect trees, water trees, and keep them from harm. Be a tree lover!! We all need trees!!


Top 10 Questions

November 2013

Thanks to Brian Jorgenson, City Forester, Boise; and Michelle Youngquist, Educational Coordinator, Idaho Forest Products Commission for the answers.

  1. How come tree bark is hard?

    Tree bark is designed to help protect all of the parts that are growing inside of the tree trunk. Bark protects trees from animals, sunlight and anything that could harm the tree. Some insects can get through, but the hard bark helps protect the tree from minor attacks. (From Brock at Owyhee Harbor Elementary in Boise)

  2. How deep do tree roots grow?

    Many people do not know. What we know more clearly is that about 90 percent of the tree roots are in about the top two percent of the soil, and they are not just right under the tree. Tree roots grow similarly to the top of the tree. They branch out and go in many different directions. Some are deeper and some are more near the surface, but they grow well beyond the actual canopy of the tree itself. Roots next to the tree trunk are large and they help support the tree in the ground. As the roots grow into the soil, they get more and more narrow, even smaller than a hair on your head. Most of the roots that absorb water are near the surface. Roots are important to the survival and health of a tree and need to be taken care of. (From James at Riverside Elementary School in Boise)

  3. How does a tree grow?

    Trees start to grow from a tiny, little seed that needs land and a favorable spot for it to sprout. Sunlight and water need to be just right for that seedling to sprout. It then will put down roots into the soil and start to grow. Once they get enough leaves or needles for photosynthesis, they can make more food for themselves. As they do, they are able to make more shoots that make them taller. Then they are able to make more layers of wood every year, which we see as the rings in the trunk. This allows them to become taller. They will continue to grow as long as the conditions continue to be right. (From Abbyerica at Rawson Elementary School in Melbourne, Australia)

  4. Why do tree branches grow in different directions instead of straight up like the trunk?

    Tree branches grow in many different directions. This allows them to gather sunlight. The leaves are factories that produce food for the tree. If they only grew up, they could only collect sunlight at a certain time of day to soak up that food. (From Alex at Owyhee Harbor Elementary School in Boise)

  5. Why are there deciduous trees and non-deciduous trees?

    It has to do with the huge variety of environments where trees grow. They have many different environments to cope with. If they happen to be growing in an environment that is cold and where the growing season is short, needles would be advantageous for them where they only lose a few needles a year. When a tree looses all of its leaves at once, it is a deciduous tree. These trees then grow new leaves the following spring. The leaves or needles a tree produces has to do with where the trees are growing, the different varieties of habitats, and that they may have to contend with different adaptations given their habitat. (From Olivia at Riverside Elementary School in Boise)

  6. Why do leaves on some trees change color?

    As yellow trees get ready for winter, they dismantle the chlorophyll, and what remains are the yellow leaves. The red leaves are a product of sunlight and the tree getting ready for winter. Some trees have a brownish color like they are cooked by the sun. There are colors in between too. (From Amanda at Owyhee Harbor Elementary School in Boise)

  7. What is the tallest tree in the world?

    It's a redwood tree in California. It is nicknamed Hyperion, and when I last saw it, it was 379 feet tall. (From Ike at Cynthia Mann Elementary School in Boise)

  8. How can you tell how old a tree is by the rings?

    Generally speaking, a tree will add a new ring to its trunk every year. You can find out how old a tree is by counting its rings. The rings also tell you about growing seasons, whether they are long or short, and the rings will look different depending on the season in which the tree grew. (From Kylie at Dalton Elementary School in Dalton Gardens)

  9. How do trees make maple syrup?

    Maple syrup comes from maple trees. Sugar maples can give you the best syrup. Trees are tapped in the fall and the sap comes out of the tree. It takes a lot of sap to make just one pint of syrup. Gallons of sap are boiled down to a more concentrated liquid, and that liquid becomes syrup. (From Gabby at Cynthia Mann Elementary School in Boise)

  10. Why is sap found in trees?

    The sap flows through the tubes from the roots to the leaves. This allows the tree to get its nutrients and grow. In photosynthesis, trees take water and nutrients from the soil, sunlight as energy, and they take in carbon dioxide through their leaves and needles. Through that process, they make all the food they need to grow. (From Amy at Cynthia Mann Elementary School in Boise)