Why Do Leaves Have Different Colors In The Autumn? And Why Do They Fall Off?

When you look at a group of trees in the summertime, you see only one color: green. Of course, there are various shades of green, but it looks as if they were all painted by one brush, after all, no matter what shade it is, its just green. But in the autumn, these same leaves take on a whole variety of colors as if they were painted again. Where do then, all these colors come from?

Well, to begin with, as most of us know, the green color of leaves is due to chlorophyll. Chlorophyll is the complete food factory that is found in each leaf. Two-thirds of the color of the leaves which is their pigmentation, are due to this chlorophyll itself. Now, there are of course other colors present in the leaf, too, but there is so much chlorophyll that we usually do not see them. 

What are some of these colors? A substance called "xanthophyll", which consists of carbon, hydrogen and oxygen, is yellow. It makes up to 23% of the pigmentation of the leaf. Carotin, the substance which gives carrots their color, is also present in the leaf and roughly makes up 10% of the pigment. Another pigment present is anthocyanin, which gives the sugar maple and the scarlet oak their bright red colors.

During the summer, we see none of these pigments other than green, right? When it becomes cold, the food that has been stored away in the leaf by the trees begins to flow out to branches and trunks. Since no more food will be produced in the winter, the chlorophyll food factory closes down and the chlorophyll disintegrates. And as the chlorophyll disappears, the other pigments that have been present all the time become visible. Thus, the leaves take on all those beautiful colors which we love seeing!

Before the leaves fall, a compact layer of cells is formed at the base of each leaf; then when the wind blows, the leaves are dislodged or are separated from the tree. On the twig there is a scar that marks the former position of each leaf.

And at the end, most evergreen trees don't shed all their leaves at the approach of winter, but lose them gradually throughout the year and so they are always green; thus evergreen!

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