Why do leaves change colour?

Tree leaves get their usual green colour from a chemical called chlorophyll. All green plants use chlorophyll to create nutrients using sunlight energy, water, and carbon dioxide. This process is called photosynthesis.

During the winter, there’s not enough sunlight or water for trees to continue making their own food. As the days get shorter during the fall, trees produce less and less chlorophyll.

This allows other colours like orange and yellow to appear in the leaves. These colours were there all summer, but were hidden by the green chlorophyll.

The reds you see in fall are because of food still trapped in these leaves.This red pigment allows trees to recover nutrients from their leaves before they fall off.
The brightness of fall colours varies from year to year. The best colours come when there’s been: