First, let’s talk about what trees do all year round. Each leaf on a tree is like a tiny solar panel, gathering sunlight to make food. Sunlight helps turn water and carbon dioxide into oxygen and glucose, a sugar that the tree uses for food to grow.
This process is called photosynthesis. A chemical called chlorophyll helps the process of photosynthesis occur. Chlorophyll is also what gives plants their green color.
As autumn begins, the days get shorter. With fewer daylight hours, leaves are not able to make as much chlorophyll. As the chlorophyll fades, we are able to see other colours, such as orange and yellow, emerge.
If a tree doesn’t receive enough water, the leaves will die faster and fall to the ground. If there is too much rain, the tree won’t receive enough sunlight, and the leaves will not be brightly coloured.
Each leaf actually has small amounts of other colours in it all year-round, even if we can’t see them. During the spring and summer, chlorophyll overpowers the other colors, and all we see is green. With less chlorophyll to give the leaf its vibrant green colour, we begin to see the other colours, such as orange, yellow, and red, which have been there all along.