If Michigan has a seasonal selling point, it’s got to be autumn.
By autumn, the humidity has lifted, the air grows clean and crisp, and the trees begin to put on their annual display of glory. Depending on where you live, you may see more colors than other regions do, as evergreens comprise a large percentage of Michigan forests. But for those who get to bask in a vibrantly colored backyard or enjoy a fiery commute during the fall months, there’s a reason for all the radiance.
Most of us are familiar with the basic concept of photosynthesis—the process by which plants harness sunlight to create nutrients that they can use for growth. Think of it as plant metabolism. Now the chemical that plays a vital role in this metabolism is called chlorophyll. Chlorophyll exists in every plant’s leaves and acts as the engine for fueling the metabolic process, capturing sunlight and using its energy to convert carbon dioxide and water into carbohydrates. These carbs function for greenery the same way they do for us.
Here’s the fun part: chlorophyll, and all the other chemicals present in a tree’s leaves, have their own colors.
Chlorophyll’s naturally occurring pigment is green, while other chemicals possess orange, yellow, and red hues. The color of a leaf, therefore, is an indication of which chemicals are most predominant in the leaf at any given time.
During summer, sunlight is at its peak, which triggers a leaf’s production of chlorophyll so it can take advantage of all the energy available through the sun and heat. With all this fresh chlorophyll constantly being cranked out, the other pigments are temporarily drowned out—leading to the green we see throughout the warmer months.
Come autumn, however, we begin to see and feel the shift in weather. Sunlight becomes sparser, clouds thicken, and a chill settles in. All of these factors reduce a leaf’s production of chlorophyll as photosynthesis slows to a gradual halt, and the internal equation of each leaf changes. Chlorophyll and its pigment give up center stage, and the green veil is lifted, allowing the other chemicals a chance to showcase their true colors.
Different chemical composition of various tree types leads to the color contrasts we see between species.
Additionally, varying temperatures and sunlight exposure create nuances between the different shades we see in members of the same tree species. Hence the vast array of colors we can see in a simple drive across town.
Much like we adapt our wardrobe as the seasons turn, trees will be putting on their autumn attire all across the country this month and next. So remember to enjoy that blaze of glory before we dive back into the snow and ice that give Michigan its reputation.