Fall Colors – What Causes Those Amazing Colors?

fall colors

Fall in the Maroon Bells Wilderness in Colorado

Have you ever wondered where those amazing fall colors in the Rocky Mountains come from?  It is due to different chemical interactions inside of the leaves.

It is always so nice to go from the hot, sunny days of summer to the cool, crisp days of fall when the mountains become covered in yellows, oranges, and reds.   I love watching how the trees begin changing colors, slowly at first and then wham, the slopes are a beautiful mosaic of colors.  Some trees turn red and others yellow.

fall colorsFall Colors – Chlorophyl Makes Leaves Green During Summer

As you recall trees and plants make their own energy by the process of photosynthesis.  Inside the leaves is something called chlorophyl – a chemical that helps make photosynthesis happen.  There is a lot of chlorophyl inside of the leaves, which has a green color.  All of this chlorophyl makes the leaves appear green during the summer while photosynthesis is happening.

Aspen trees in the fall, fall colors

Aspen trees in the fall

Photosynthesis Stops In The Fall

In the fall, as the days get shorter, the leaves stop photosynthesis and the chlorophyl disappears.  This means that the green chlorophyl is no longer in the leaf.  The lack of all of this green from the chlorophyl allows the natural yellow and orange colors of the leaves to come out and be visible in the fall.

Yellow And Orange Colors Are Already In Leaves

I just want to restate what I explained above so that it is clear.  The yellow and orange colors that appear on leaves in the fall were in the leaves the entire time, but they were hidden behind the abundance of green chlorophyl.  In the fall as the trees stop photosynthesizing the green disappears and the orange and yellow are revealed.

Red Maple Leaves, fall colors

Red Maple Leaves

Other Chemical Changes Also Take Place To Cause Fall Colors

There are many different chemical reactions taking place inside of the leaves in the fall.  Some of the magnificent red, purple, and brown colors that appear in the fall are due to these other reactions.

What Makes Some Leaves Red?

Some leaves, like leaves from Maple trees, turn red.  These trees leave some of the food produced during photosynthesis in the leaf.  Then the cold nights of fall combine with sunlight during the day to change that leftover food into a red color.


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