Leaves are food factories of the tree. Powered by sunlight, the green substance in leaves, called chlorophyll, uses carbon dioxide and water to produce life-sustaining carbohydrates. The entire process is called photosynthesis. Leaves are also responsible for respiration and transpiration.

A tree's leaf is one major marker that helps in keying out and identifying any species of tree. Most trees can be identified by the leaf alone.

As you can see in the illustration, leaves come in many shapes and sizes. The "star" shape of sweetgum is totally different from the heart-shaped leaf of an eastern redbud. Note that leaves can be described by observing their base, their margin and their tip or apex. Each characteristic has a name and is used a part of the identification process.

Click on the illustration above for a better look at shapes (USFS-TAMU clip art).

Also a leaf can either be simple (no extra leaflets) or compound (three or more leaflets). On a compound leaf, all leaflets are attached to a single leafstem or rachis.

Click on the illustrations below for a better look at compound leaves (USFS-TAMU clip art).

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