In Season

Autumn has arrived outside my window in Brooklyn, and with it, the turning of the leaves and the artistry that announces their impending absence. In botany, temperate trees that forfeit their foliage in follow with the seasons are called deciduous. By contrast, trees that retain their verdancy all throughout the year are known as evergreen. The word deciduous itself means “falling off or shed seasonally or at a certain stage of development in the life cycle.” Trees that fall under this description are more than a vibrant display of nature’s virtuosity; they offer an elegant map for navigating the passage of time.

During summer, deciduous trees are easily recognizable by their large leaves; think of the star-shaped maple and chestnut leaves that stretch out in every direction, the longness of willow leaves, elliptical elms. Meanwhile, evergreen leaves tend to have less surface area; think of the thinness of cedar leaves, the narrowness of pine needles, slender spruces. Deciduous leaves grow generously in order to capture maximum sunlight during summer months so that the trees have enough energy to last them through winter when dwindling daytime means less light and water in leaves would freeze—a form of forecasting for the future.

As temperatures drop with the arrival of autumn, hormones in deciduous trees trigger a process known as abscission. The trees begin to absorb the nutrients of their leaves, transferring it to their roots for safekeeping—to eventually serve as reservoirs for winter. Among the molecules broken down is chlorophyll, which makes the leaves appear green. As this pigment recedes, these leaves begin to take on red, orange, and yellow hues. At the end of this natural process, they begin to fall off—each fragment of foliage having fulfilled its purpose.

Come winter, abscission has allowed deciduous trees to conserve energy by removing their most vulnerable parts. Holding onto their leaves would require a great deal of sustenance in order to repair and maintain them amidst the harshness of the freezing cold—as is the case with evergreen trees, which need more nutrients to stay in good condition consistently throughout the year. Thanks to their preparation during preceding seasons, deciduous trees are able to survive the winter with fewer needs. They can rest with branches bare before blooming again.

When the birds sing of the return of spring, barren branches serve another purpose: propagation. Many deciduous trees and other plants flower when they are leafless. With barren branches and empty appendages, chances increase for pollination by wind as well as winged visitors that might otherwise miss the flowers. This approach is not without its dangers; when temperatures fluctuate, these flowers can be frozen by frost, left exposed to the elements. When the time comes, deciduous plants take the risks required of regeneration.

Deciduous trees are an extraordinary example of what it looks like to live in harmony with the cycles of nature—and what hangs in the balance should fossil fuel pollution continue to wreak havoc on our climate and the intricate and delicate processes that depend on it. As Atmos social media editor Elie Gordon pointed out in a recent post, of all the seasons, autumn may be the first casualty of climate change; research has found that, with higher temperatures and therefore more productive summers, trees start shedding their leaves earlier, significantly impacting their ability to capture and store carbon from the atmosphere.

I wonder if evergreens envy the progression of their deciduous kin—if firs and hemlocks long to lose their leaves and change colors with the weather. I wonder if ashes and rowans ever wish they could make the seasons stand still, to stay the same. However perilous the path, this willow would rather be deciduous any day. I would rather savor the sweetness of the sun and be mindful of the future. I would rather release my grip on the past and show how glorious it can look to let go of what’s no longer working. I would rather use my energy wisely and repose when the time is right. I would rather risk it all and watch our world come alive again. Wouldn’t you?