In many parts of the world, autumn turns forests into blazes of yellow, orange and red. But where do these bright shades come from? The answer is hidden inside every leaf.
During spring and summer, leaves are busy making food for the tree. To do this, they use sunlight, water and air. A green substance called chlorophyll captures the energy from sunlight. There is so much chlorophyll in a leaf that it hides all the other shades.
As autumn arrives, the days grow shorter and there is less sunlight. Trees such as maples and oaks begin to get ready for winter. They stop making chlorophyll. As the green fades away, the yellows and oranges that were in the leaf all along begin to show.
Some trees, such as certain maples, also make a brand-new red substance in autumn. This is why some leaves turn bright red or purple.
Finally, the tree seals off each leaf where it joins the branch. The leaf dries out and falls. Without leaves, the tree uses less water during the cold winter months. In spring, new green leaves will grow, and the cycle will begin again.
