This fall seemed to sneak up on me as time has been simultaneously moving at a rapid pace and in slow motion. As someone once told me when I became a parent, “the days are long, but the years are short,” and this global pandemic brings those words even closer to home. Nevertheless, I took the time to slow down and bask in the beauty of the changing fall leaves this October. For me, nature is truly restorative, and there aren’t many things more beautiful than driving through the mountains of Western Pennsylvania during peak color change.
But, why do leaves change their color?
During the warmer months in Pennsylvania, trees take advantage of the increasing amount of light and good weather available from longer and warmer days. Using their leaves, trees absorb energy from sunlight, breathe in carbon dioxide, drink up water to produce their own food sources – sugar and starch. This process is only possible through chlorophyll housed in the leaf cells – giving leaves their vibrant green coloration.
Leaves also contain other color pigments ranging from yellow to orange – these pigments are often masked by great amounts of green coloring. But in the fall, the tree begins to prepare for shorter days and colder weather, and the leaves stop their food-making process. To prepare for the upcoming winter, the chlorophyll begins to break down, causing the green color to disappear. This change allows the ever-present yellow, orange, and red pigments to become visible. While chlorophyll breaks down, other chemical changes in the leaves can occur, creating an additional ray of colors through the development of red anthocyanin pigments. The yellow and orange pigments mixed with the red anthocyanin pigments give rise to the reddish and purplish fall colors of trees, such as dogwoods and sumacs.
Each species of tree shows off their own fall color. All these colors are due to the mixing of varying amounts of the chlorophyll residue and other pigments in the leaf during the fall season. This winter preparation creates a nature show like no other.
Another aspect of the leaves changing colors is that those leaves will eventually drop to the ground. Most of the broad-leaved trees in Pennsylvania shed their leaves in the fall (some trees retain their dead leaves until new growth starts in the spring). So, what should you do with your leaves in the fall? According to the U.S. Environmental Protection Agency, leaves and other yard debris account for more than 13% of the nation’s solid waste—33 million tons a year. In typical landfills, there isn’t enough oxygen to decompose the yard waste, causing the development and release of the greenhouse gas methane.
So, what do I do? LEAF IT! (get it?). Leave your leaves where they fall in the fall – or at least, find a nice place in your yard to pile the leaves. Leaf litter can act as both a fertilizer returning the nutrients back into the ground, and as a weed suppressant by acting as a ground cover. Leaf litter is also a vital habitat for much of our favorite wildlife. Many critters – from insects to mammals and everything in between – rely on leaf litter for food, shelter, and nesting material. Many of our favorite moth and butterfly caterpillars overwinter in fallen leaves before emerging in spring! So, if you want free mulch and fertilizer, to create wildlife habitat, and have more free time – LEAF IT!
Heather Hulton VanTassel is Assistant Director of Science and Research at Carnegie Museum of Natural History. Museum employees are encouraged to blog about their unique experiences and knowledge gained from working at the museum.
