Describing the Structure of Trees

This science article looks at parts of a tree including its leaves, branches, trunks and roots.

Arbre du Tenere. The most isolated tree on the planet in middle of the desert

Click for slide show

What are trees?

Trees are just very big plants with long stems and thick stems! We call the long and thick stems of trees ‘trunks’.

It took millions of years for plants to change into trees. There was a very good reason for plants growing taller. Ancient plants grew taller so they could get more sunlight than other plants.

Rainforest canopy illustrating how trees have to compete for light

If you were a short plant, you did not get much sunlight! If you wanted any sunlight you needed to grow taller and become a tree!

Looking up through small gap in rainforest canopy showing how dark it is on rainforest floor

As trees grew taller their trunks also grew thicker!

Redwood National Park, California showing bottoms of trees

Parts of a tree-the trunk

Some trees grow very tall trunks and thick trunks such as this giant sequoia.

boy hiding at the bottom of a giant sequoia tree

Look how tall this giant sequoia is! This one is called the ‘Grizzly Giant’!

Grizzly Giant, Yosemite National Park. An amazingly tall and thick tree

Other trees grow trunks that are very tall and narrow..

eucalyptus trees have tall and narrow trunks ,Kerewong State Forest, NSW, Australia.

some trees grow very thick trunks like this tree in Mexico….

Arbol del Tule, famous Mexican tree with incredibly wide trunk

…while other trees grow trunks that are not tall or very wide. Tree trunks come in all shapes and sizes!

AppleTree in full bloom showing how some trees are neither tall nor have wide trunks

Parts of a tree- the roots

Most of the time you cannot see the roots of a tree because they are under ground. The roots of a tree keep it safe and stop it falling down.

baobab tree in Madagascar with incredibly thick trunk and small amount of foliage

 Sometimes you can see the roots of trees.

  • Is it good that you can see the roots of this tree? What has happened?

tree blown over in storms exposing the roots, Granby, Missouri, USA

You can see half the roots of this mango tree because some of the ground has been washed away by a river.

  • Will this tree stay healthy?
river bank washed away exposing tree roots

Aaron1a12 at en.wikipedia

Sometimes the roots of  healthy trees can be seen above ground.

 tree roots above ground on rocky terrain, Cliffs of the Neuse State Park, Wayne County, North Carolina

  •  How do roots help a tree to grow and stay healthy ?

Parts of a tree-the bark

Bark is the skin of a tree. Bark stops trees from losing of water. Bark also stops trees from getting diseases. Bark stops trees being damaged by insects and animals.

Asian long horn beetle sitting on tree bark

The patterns on bark can be very beautiful. This is the pattern of bark on a maple tree.

wavy patterns of bark on a Japanese Maple tree

This is the bark of a silver tree!

  • What does it look like?

 unusual pattern of bark on a silver tree looking like a human being in San Francisco Botanical Garden

Parts of a tree- the branches

The large branches are called ‘boughs’. The smaller branches are called ‘twigs’.

  • Can you see the ‘boughs’?

branches of a Scots Pine taken from the bottom of tree looking upwards

  • Can you see twigs?

boughs and twigs joined together at the top of leafy Platanus x hispanica trees

Parts of a tree-the leaves

We also know that leaves are green because that is the color that soak up light the best. Trees need to soak up light to help give them energy.

beech trees bathed in sunlight,Grib Forest in the northern part of Sealand, Denmark

Malene Thyssen, http://commons.wikimedia.org/wiki/User:Malene

  • Sponges soak up water. What do green leaves of trees soak up?

sponge illustrating analogy of how sponges soak up water and green leaves soak up light

Leaves of trees come in all shapes and sizes. We call the leaves of some trees ‘needles’.Needles were once ‘broad’ leaves that rolled up millions of years ago.

Rolled up newspaper illustrating how pine needles are rolled up leaves

clump of pine needles from a Longleaf Pine tree

  •  Why do we call these leaves ‘needles’?

Sewing needles demonstrate why pine needles are called by that name

We call these leaves ‘broad leaves’. Look at all those amazing shapes!

Broad leaves come in all sorts of shapes and sizes

Leaves come in some amazing colors.

  • Can you describe the colors? What time of year do you think this is?

Japanese maple leaves of all different colours fallen to ground in fall

Forests have trees full of leaves with amazing colors!

Vermont fall foliage Hogback Mountain

Science projects- parts of a tree

  • Identify the leaves of different British trees at Shurdington.org
  • Suggested science projects about trees at Nature Detectives
  • Look at a tree. Can you see the trunk, boughs, twigs and leaves?
  • Draw tall trees with narrow trunks. Draw short trees with thick trunks.
  • Find different trees and leaves. Do ‘bark rubbings’ and leaf rubbings’.Compare the patterns.
  • Examine different leaves with magnifying glasses. Can you draw what you see?
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