What is tree bark?

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You’ve probably noticed that the stems of many plants are green and smooth. But what about the stems of woody plants? For example, why are tree trunks brown, bumpy, and hard? This is because the trunk, branches, and roots of a tree are covered with bark! Tree bark is the outer tissue of the tree. 
Did you know there are two kinds of tree bark?! The inner bark is soft bark that helps transport food from the leaves to the rest of the tree. It is made of tissue called phloem. When phloem dies, it becomes part of the outer bark. The outer bark, also known as rhytidome, is made mostly of dead tissue.
Why do trees need bark? For one thing, bark is like armor for trees and protects them from damage by creatures, and from organisms that can make the tree sick. Bark also protects trees from severe heat and cold, as well as from harsh sunlight.  Bark even helps prevent water loss from the tree!
by   (whyzz writer)
  • Further information

    As a tree grows thicker, the outer bark becomes too tight, much like a coat you’ve outgrown! The outer bark then splits, creating the cracks and patterns that give a tree trunk its texture. Many items we use come from bark, including cinnamon, dye, mulch, and medicine.
    Is all tree bark the same? Absolutely not! Bark comes in a variety of shades, from brown or black to gray or silvery white. Some bark is spiny, while other bark is smooth, scaly, or covered with ridges.  It can be fun to learn how to identify trees by their bark, or simply to observe the colors and textures of the bark that covers the trees in our yards!
  • Exploration

    Create a tree bark rubbing! Use tape to secure a piece of white typing paper to the side of a tree trunk. Make sure the paper is fastened well! Now peel the paper off the outside of a crayon in the color of your choice. Hold the crayon so it is sideways and the entire length moves up and down with your hand. This will allow you to get as much color and texture as possible. 
    Now rub the crayon over a section of the tree! Do you notice how the bumps in the bark are appearing on the paper? This type of art is called a rubbing! When you’ve finished, you may even choose to cut out a tree trunk shape from the decorated paper, then glue it to another piece of paper and add your own leaves. The bark of the tree in your picture will look like the bark of the real tree you used for the rubbing!
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