Why Do Leaves Change Colors in Autumn?
In autumn, the leaves of many trees turn from green to shades of scarlet, gold, orange, and purple. Jack Frost is usually given credit for autumn colors, but frost has very little to do with it. The green we see in leaves all summer is due to chlorophyll.
This green coloring matter acts like a little food factory, manufacturing food for the tree. Other colors – yellow, orange, red, and purple – are present in the leaf, too, but there is so much chlorophyll that we usually can’t see them.
In the autumn, because of changes in the length of daylight and changes in temperature, the leaves stop making chlorophyll, and then we can see the other colors.
At the same time other chemical changes may occur, which form additional colors through the development of 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.
The autumn foliage of some trees show only yellow colors. Others, like many oaks, display mostly browns. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season.