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Well, it’s that time of the year again when leaves change colors hinting of the new winter. Autumn, for many of us, is a favorite season. It’s certainly colorful, as evidenced by thousands of leaf-peepers that travel here from points south. The daytime temperatures are comfortable and the crispy nights are pure delight. It’s hard to rouse myself when I’m snuggled deep under the bed sheets, even to witness the often spectacular pink and crimson pre-dawn light.

In the U.P., a sure sign of fall is the abundance of beets, cabbage, and apples for sale. The bow hunters are getting excited. The bracken fern has browned. Most of the hay has been stored up. Bats, monarch butterflies, waterfowl, and other animals have migrated or are getting ready to move to their winter sites. The asters are bursting into their prime color. Crazy people are wearing a lot of green and gold. Life is good in the fall.

Most people have taken notice of pre-season color changes. Annual debates resume whether the fall color began earlier or later than normal. Usually it’s the red maple that first flags the sea of green. August color change is a result of tree stress; either parts of trees or entire crowns can turn early. These early trees may be the harbingers of fall but are not yet the “real” thing. In September, black ash turn yellow, heralding the first authentic wave of fall color. Black ash is the first species to turn, and the last to leaf out in the spring. Sometimes I wonder how these “short-timers” can be successful. But they are.

The physiological processes of nutrient retention and dormancy are complex and quite interesting, if you can master the ten-dollar terms. Longer nights, shorter days, and nighttime temperatures jump-start the fall spectacular. Leaves change color because chlorophyll breaks down, that magical chemical essential to the process of converting sun energy into food and producing oxygen. Chlorophyll and other chemicals absorb all the colors of the rainbow except green. That’s why we see green during the summer. It’s the color that plants “throw away.” As chlorophyll molecules disappear, different bands of light reflect from the leaves. More persistent companion chemicals become dominant and, for a short time, cause leaves to appear in autumn splendor unmatched anywhere else in the country.

As my thoughts digress into this chlorophyll idea (digression beats relearning the ten-dollar plant physiology terms), I realize there’s irony in the perception that green, the least useful color of the spectrum, is associated with healthy and lush plant life. Most of the year is not green in the U.P., in fact about two-thirds of the year. I suppose you even could call the green season unusual or atypical. I chuckle as I think of the misplaced symbolism expressed in the “green” political party. Does that mean it’s the least useful of political parties? Or perhaps, the party is not as it appears (well, it is politics)? Most of the year, our temperate vegetation is brown. Maybe they should call themselves the brown party? As chlorophyll disappears for the season, I’ve yet to hear these folks declare impending doom due to a lack of global oxygen as the northern “factories” shut down for six to eight months of the year. It seems nature has built in some reasonably powerful accommodation for such huge changes in atmospheric and biological cycles.

But back to the subject at hand, maples are the royalty of fall as they phase to brilliant shades of scarlet and gold. It can be eerie to stand under a bright gold forest canopy on a sunny day. Some of nature’s most “unnatural” colors occur in the fall. Bright dry days and frosty nights make red oak a rich burgundy. There are some bizarre purples in some of those oak leaves. Aspens, birches, and basswood turn varying degrees of yellow. The smoky gold of tamarack is my personal favorite, except when the needles get stuck down the back of my shirt. Even the needles of pines, spruces, cedars, and firs turn yellow and drop off. Two or three year old needles drop off each year to enter the stream of recycled chemicals and nutrients.

For plants and animals, I don’t think the fall color change has any particular meaning. They are simply busy carrying out their role in the biota, much like the parts of a great machine. Only we, as humans, have the capacity to wonder and to appreciate the design of things. A mouse doesn’t recognize beauty in the fall canopy. It only knows that it will soon be more exposed to hawks and owls. Herein, perhaps, is the major difference between people and other living things. And the colors of fall, in concert with the myriad of other seasonal changes, serve to punctuate that difference. Yes, life is, indeed, good in the fall.

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Bill Cook is an MSU Extension forester providing educational programming for the entire Upper Peninsula. His office is located at the MSU Upper Peninsula Tree Improvement Center near Escanaba. The Center is the headquarters for three MSU Forestry properties in the U.P., with a combined area of about 8,000 acres. He can be reached at cookwi@msu.edu or 906-786-1575.

Prepared by Bill Cook, Forester/Biologist, Michigan State University Extension, 6005 J Road, Escanaba, MI 49829
906-786-1575 (voice), 906-786-9370 (fax), e-mail: cookwi@msu.edu

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Last update of this page was 5 November, 2018