Want to appear smart at the next dinner party you attend? If so, then there is no better way than to engage in an impromptu soliloquy about why leaves change color in the fall. But before you get on your soapbox and start raising your glass to the wonders of foliage, let’s make sure you have an understanding of the incredible transformation that’s taking place.
You can’t understand why leaves change color without first understanding the role of chlorophyll and photosynthesis. In a nutshell, chlorophyll is both what makes leaves look green and allows trees to survive; it helps plants convert sunlight into energy in the form of glucose.
But this method of producing energy isn’t sustainable year-round, because come wintertime, the days are shorter, drier, and less sunlight is available. The trees—smart little buggers that they are—use the onset of winter and less sunlight as their cue to head into a sort of survival-style hibernation mode whereby, in an effort to conserve stored energy, they drop their leaves.
“But trees don’t drop green leaves,” an interested dinner party guest may contend.
This is true. So why don’t trees do this, and what exactly is taking place when leaves change colors?
As mentioned, when water and sunlight become scarcer during the winter months, the trees look to conserve energy and chlorophyll in any way possible, so they stop sending water to their leaves. This forces the chlorophyll—what gives the leaves their greenish color—to fade. Trees, somewhat miraculously, reabsorb and save the chlorophyll molecules in wintertime and redeploy them in spring—a process that saves them considerable energy and allows them to avoid creating chlorophyll from the ground up.
It is precisely when this chlorophyll fades and is reabsorbed by the tree that leaves “change color.” The absence of green gives other colors the chance to shine, most notably, the yellow-orange-ish pigment called carotenoid (found in foods like pumpkins and carrots), and the red-purple-ish pigment called anthocyanin (found in foods like cherries, raspberries, and blueberries). While trees may produce some of these pigments in an effort to protect themselves from the sun and herbivores as it reabsorbs their remaining stores of chlorophyll, it’s important to note that foliage is less about a changing of colors and more about a revealing of colors that were there all along and couldn’t be seen because of the abundance and vivacity of chlorophyll.
You’re now equipped with the knowledge and know-how to successfully woo an entire dinner party if you so choose. But at the very least, let this information be a testament as to why we’re so attracted to foliage in the first place: it is beautiful, yes, but it’s also a magnificent sight to see the survival mechanism of trees in unison, en masse.