I recently saw a photo of rolling hills covered in shades of greens, yellows, oranges, and reds with the caption “My favorite color is October.” Kind of sickly sweet, but it made the point well: October in northern New England is a stunning time. Even going on a short drive that offers a change in elevation or ecosystem displays a seemingly impossible variety of colors on the landscape.

But why do leaves change color in the fall? A surprising number of people do not know–even in New England where these colors define the season and draw “leaf peepers” from around the world. Simply put (i.e. the statement you can whip out when someone asks you about fall colors so you can feel wicked smart), the green chlorophyll in the leaves starts breaking down as the daylight hours dwindle, revealing other colors that were hiding in the leaf beneath the domination of the greens of summer.

Want more detail? Chlorophyll exists in leaves to help facilitate the process of photosynthesis, where plants absorb carbon dioxide, water, and sunlight to produce oxygen and sugars. This can happen easily during the times of year when there are ample daylight hours, but is not particularly profitable when there are more hours of darkness per day than sunlight. As the days start getting shorter in the fall, plants take the cue to stop focusing on the whole chlorophyll thing and let that break down. Once that dominating green chlorophyll is out of the way, other pigments hiding in the leaf, such as anthocyanins and carotenoids, reveal their colors before the leaves fall off altogether.

Autumn leaves

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