Mother Nature is starting to put on her annual fall show. The performers have been rehearsing for weeks. Considering the majority of trees we enjoy in southern Idaho are not native to this area, we’re lucky to usually get a good show of autumn color.

I’m pretty sure that somewhere along the line someone tried to teach you why leaves change color. Some of you might even remember. For those who don’t, here’s a short class that we’ll call Autumn Leaves 101.

Several factors play a role in fall color; geography, length of day, weather and plant pigments. The New England states, with hills of deciduous forests full of maple, oak and sweet gum, are best known for this eye-popping display. It’s a tourist hot spot in the fall where the ‘leaf peepers’ flock to hopefully catch the peak of the autumn color.

Three main pigments make up the color in leaves. Chlorophyll, the green and most dominant color. Carotenoids, responsible for yellow and orange. This is the same pigment found in corn, carrots and sweet potatoes. Anthocyanins are the reds and purples also found in purple grapes, cranberries, strawberries and blueberries. Most of the year green chlorophyll hides the other colors. When the weather gets cooler and the days shorter, the tree no longer manufactures chlorophyll, the green color fades and the other colors are finally allowed to show off, much to our delight.


The yellow/orange carotenoids are always present and fairly consistent from year to year. Anthocyanins are only manufactured in autumn and not all trees manufacture them, thus the clear yellow of some trees like ginkgo, aspen and honey locust. Reds are usually more vibrant depending on the weather and when mixed with the carotenoids we get the bright orange color seen in some maples and sumacs. Researchers have recently discovered that the anthocyanins actually help the tree recover nutrients from the leaf before it drops from the tree. Ahhhh, science.

Best conditions for great fall color?  A warm, wet spring, a summer that’s not too hot and dry and a fall with warm, sunny days and cool (below 45 degrees), but not freezing nights. An early freeze kills the leaves quickly and pretty much ends our chances for some wonderful fall color.  Rainy days near the time of peak color will weaken the intensity of the color.

Some trees with good yellow and gold autumn color are Norway maple, honey locust, poplar, tulip tree, linden and ginkgo.

For red and orange color look for sweet gum, pear, sugar maple,  flowering dogwood, amur maple, sumac and hawthorn.

If you are buying a tree specifically for fall color, select one in the fall when you can actually see the color because genetics play a part in the color, too.

Enjoy a walk in a park, a bike ride along the river, a drive to the mountains a stroll through your neighborhood or at least look out your window. Whatever you choose, realize how lucky we are to enjoy an autumn day in Idaho.


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