Autumn splendor - Why do leaves change their colors?

Just as autumn's cool breeze will soon replace summer's sweltering heat in many parts of the country, one of nature's most awe-inspiring phenomena is on its way!

While the seasonal change is always much appreciated, it is also often misunderstood. A common misconception is that cold weather is responsible for the changing colors. While temperature can have an effect, it is just one factor that plays a part in painting a striking fall landscape.

To properly understand the science behind autumn colors, we need to dig a little deeper into the chemical processes going on within the leaves. 

During Spring and Summer, leaves use energy from sunlight to transform carbon dioxide and water into sugars and starch, the foods necessary for the tree's growth. This important food-making process requires numerous cells containing chlorophyll, an important chemical that gives the leaf its green color. 

In the fall, due to the decreasing length of daylight and to a lesser extent, changes in temperature and groundwater supply, the leaves stop their food-making process. This causes the chlorophyll to break down and the green color to fade. 

Once chlorophyll production stops, yellow and orange pigments, masked by green pigments, become visible. However, this only gives the leaves a part of their fall splendor. Other chemical changes bring out additional colors by developing 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.