Why Do the Leaves Change Colors in the Fall?

Fall is a great time of the year. With pumpkin and apple picking, hayrides, football games, and even the changing color of the leaves. But why do the leaves on trees and shrubs change color this time of year?

Well, it has a lot to do with the changes in the length of daylight and temperatures. The leaves stop their food-making process. The chlorophyll breaks down, the green color disappears, and the yellow to red colors become visible and give the leaves a part of their autumn splendor.

To understand why leaves change colors, we need to understand what leaves are and what they do for the trees and shrubs. First, leaves are nature’s food producers.  Plants take water and nutrients from the soil, carbon dioxide from the air and then take sunlight to turn water and carbon dioxide into oxygen and glucose, a sugar. The oxygen we use to breathe and the glucose is used as food for energy and as a building block for growing. The way plants turn water and carbon dioxide into oxygen and glucose is called photosynthesis. This putting together with light produces a chemical called chlorophyll. Chlorophyll is what gives plants their green color.

As summer ends and fall begins, the days become shorter and the temperatures cooler. This is how plants know that it is time to prepare for winter.

During the winter, there isn’t enough light and warmth for photosynthesis. The trees and shrubs will rest and live off the food they have stored during the summer.  They shut down their food-making process and the green chlorophyll disappears from the leaves.

As the bright greens begin to disappear from the leaves, we begin to see the yellows and oranges. Small amounts are there all summer long, but they are hidden by the green chlorophyll.

The reds and purples are mostly made in the fall.  In some trees such as maples, the glucose is trapped in the leaves after photosynthesis stops. The cool night of autumn and sunlight causes the glucose in the leaves to turn red.

It is the combination of all these things that contribute to the beautiful colors of fall that we enjoy. After the last pumpkin and apples are picked – the wagons are put in the barn and the last leaf has dropped, it is time get out the rakes and blowers to clean up all those leaves.