The Changing of the Colors

Fall is such a beautiful time to spend in Detroit.   Each time we head up there this time of year, we are captivated by the many colors of leaves among the millions of trees.  How does this spectacular show of color happen?  Although it’s so magical, it is all very explainable and a mere matter of biology that is easy to understand when you know a few things.

First of all, leaves get their color from three different types of pigments.  Here they are, described below:

“Chlorophyll is the most important of the three. Without the chlorophyll in leaves, trees wouldn’t be able to use sunlight to produce food [and the leaves wouldn’t be green].

Carotenoids create bright yellows and oranges in familiar fruits and vegetables. Corn, carrots, and bananas are just a few of the many plants colored by carotenoid.

Anthocyanins add the color red to plants, including cranberries, red apples, cherries, strawberries and others.

Chlorophyll and carotenoid are in leaf cells all the time during the growing season. But the chlorophyll covers the carotenoid — that’s why summer leaves are green, not yellow or orange. Most anthocyanins are produced only in autumn, and only under certain conditions. Not all trees can make anthocyanin.”  Courtesy of

So how do these pigments play in the changing seasons? Simply put, as the days get shorter and the temperature gets cooler, trees produce less chlorophyll, which allows more of the carotenoid pigments to show through, hence more yellows and orange.  Furthermore, anthocyanin production increases.

But eventually, the leaves will fall.  This is because the leaves are filled with water sap which can freeze.  This makes the tree vulnerable and susceptible to danger.  The tree is better off without the leaves.  In defense, the tree seals them off and they then fall from the tree.

There is a lot more science as to why these things happen which you can read about here, and there is even a science behind what determines more precisely what color the leaves change into.  For example, this description from the US Forest Service describes how different weather patterns can affect the intensity and brilliance of the colors.

“A succession of warm, sunny days and cool, crisp but not freezing nights seems to bring about the most spectacular color displays. During these days, lots of sugars are produced in the leaf but the cool nights and the gradual closing of veins going into the leaf prevent these sugars from moving out. These conditions-lots of sugar and lots of light-spur production of the brilliant anthocyanin pigments, which tint reds, purples, and crimson. Because carotenoids are always present in leaves, the yellow and gold colors remain fairly constant from year to year.

The amount of moisture in the soil also affects autumn colors. Like the weather, soil moisture varies greatly from year to year. The countless combinations of these two highly variable factors assure that no two autumns can be exactly alike. A late spring, or a severe summer drought, can delay the onset of fall color by a few weeks. A warm period during fall will also lower the intensity of autumn colors. A warm wet spring, favorable summer weather, and warm sunny fall days with cool nights should produce the most brilliant autumn colors.”  Read more:

But the important thing to remember, is that the leaves changing color and then falling, is a defense mechanism for survival of the tree.  It knows the lack of sun can no longer fuel production, so it turns off its factories (chlorophyll) until the sun and warmth come back out again.

What do you do to survive the winter?  What are your favorite things that make you look forward to this cold, but beautiful and cozy time?   These are thoughts to ponder as the days grow short and the weather brings us inside.  We hope you all have a wonderful Fall season and as the seasons continue to move forward, welcome each day with the new opportunity and life it brings.


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