Why Do Leaves Change Color in the Fall?

Why Do Leaves Change Color in the Fall?

For parts of the country with cooling temperatures and large populations of deciduous trees, the next six weeks will provide some wonderful scenery. Green leaves will give way to a colorful natural skyline with hues of reds, yellows, oranges and browns 

But what gives leaves their fall color palette? The answer can be found in four pigments:

  • Chlorophyll

  • Carotenoids

  • Anthocyanins

  • Tannins

Present throughout the year, chlorophyll gives leaves their green color during the growing season. It is essential to the production of carbohydrates and photosynthesis. But if chlorophyll is present year-round, why don’t leaves stay green? Another pigment is also present during the growing season: carotenoids. During the spring and summer, however, high chlorophyll levels overpower carotenoids, and leaves stay green. While remaining present, chlorophyll levels dip in the fall, allowing carotenoids to become more visible. This gives leaves their yellow color.

Red color in leaves in the product of anthocyanins. As you might have deduced, orange leaves are created by the presence of both carotenoids and anthocyanins.

A pigment not found in most trees during the growing season, anthocyanins develop with cooler night time temperatures. Paired with ideal weather conditions, anthocyanins play a large role in creating more intense fall colors. A combination of temperatures between 32-45 degrees at night and bright sunny days are peak conditions for trapping sugars in leaves, allowing anthocyanins to develop and enhance color. Avoiding big storms that can pull leaves off trees prematurely also helps anthocyanins develop more completely.

The fourth pigment, tannins, typically are found in oak trees, giving leaves a dull brown color. Oaks that have been fertilized show more of a red color before tannins fully develop. Like anthocyanins, tannins are not present in growing season.                                               

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