Science with Samantha

Science With Samantha: Why Do Leaves Change Colors During Fall?

NBCUniversal, Inc.

In addition to the cooler temperatures, one of my favorite parts about the fall season is watching the leaves change color. The brilliant reds, oranges and yellows make for such a colorful time of year! 

How does this happen? It is the result of chemical processes that take place in the tree as the seasons change from summer to winter.

In the fall, we have fewer hours of daylight (sunshine) and cooler weather. When this happens, the leaves stop their food-making process, chlorophyll breaks down, the green color disappears, and the yellow to orange colors become visible. At the same time, other chemical changes can occur, which form additional colors through the development of red anthocyanin pigments. Some mixtures give the leaves a reddish or purplish color.

Temperature, light and water supply all have an influence on the degree and the duration of fall color. Low temperatures above freezing will favor anthocyanin formation producing bright reds in maples. However, early frost will weaken the brilliant red color. Rainy and/or overcast days tend to increase the intensity of fall colors. 

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