Have you ever wondered why aspens and other deciduous (seasonal leaf dropping) trees put on such an amazing display of color each autumn? Here is a simplified explanation!

As the days get shorter and nights begin to get colder, deciduous trees (such as aspens) suspend production of chlorophyll, which is essential for photosynthesis (energy production using sunlight), as an energy saving measure in anticipation of the coming winter. As the chlorophyll left in leaves breaks down (and with it the green coloring), other colors become visible.

Why aspen leaves change color during fall.

Yellow and orange colors are produced by carotenoids, which are always present in the leaves. Carotenoids protect chlorophyll from too much light exposure and help with the photosynthesis process.

Anthocyanins are responsible for the red color often found in leaves and are produced by the tree to filter out UV light while valuable nutrients are extracted.

The length of the grand display of color is closely tied to the amount of moisture around. If the environment is too dry, the leaves will quickly turn brown and fall. Similarly, a cool autumn will help to maximize the colors, but freezing temperatures can cause leaves to drop suddenly.

The process by which trees drop their leaves is called abscission.

Now you know a little more about the complicated processes that produce our amazing fall colors! Check out some of my fall color shots here.

2015 edit: You can now buy my new book, Fall Colors! Read more here or watch the video here.