Why does leaves change color

The Answer is Revealing. Right now, you might be noticing a shift in the air. Cooler temperatures serve as a reminder to pull out that puffy coat or scarf. Leaves get their green color from a chemical called chlorophyll, which helps trees take in sunlight. Trees use the sunlight captured by chlorophyll to drive a process called photosynthesis, which is how trees eat, so to speak. Tree leaves also have orange and yellow pigments. These pigments are called carotenoids, which are also responsible for the color in pumpkins and carrots.

This extraordinary chemical absorbs from sunlight the energy that is used in transforming carbon dioxide and water to carbohydrates, such as sugars and starch. Along with the green pigment are yellow to orange pigments, carotenes and xanthophyll pigments which, for example, give the orange color to a carrot. Most of the year these colors are masked by great amounts of green coloring. But in the fall, because of changes in the length of daylight and changes in temperature, the leaves stop their food-making process.

The chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible and give the leaves part of their fall splendor.

At the same time other chemical changes may occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give rise to the reddish and purplish fall colors of trees such as dogwoods and sumacs, while others give the sugar maple its brilliant orange. The autumn foliage of some trees show only yellow colors. Others, like many oaks, display mostly browns. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season.

As the fall colors appear, other changes are taking place. At the point where the stem of the leaf is attached to the tree, a special layer of cells develops and gradually severs the tissues that support the leaf. As summer fades into fall, the days start getting shorter and there is less sunlight.

This is a signal for the leaf to prepare for winter and to stop making chlorophyll. Once this happens, the green color starts to fade and the reds, oranges, and yellows become visible.

Shorter days in the fall are a signal for trees to start preparing for winter. Weather is also an important part of the color change. In the fall, the temperatures get colder and there is also more rain and snow.