Why Do Leaves Change Color in the Fall?

One of my favorite things about autumn is watching the leaves turn — but as pretty as the flame-colored foliage is, it actually serves a purpose beyond being gorgeous. If you’ve ever asked yourself, “Why do leaves change color in the fall?”, good news! We’ve got some answers — or rather, SciShow does, thanks to their latest video. Guest hosted by Michael Aranda, the video breaks down everything you ever wanted to know about why trees decide to get all naked come fall. Isn’t science fun?

The short version behind why deciduous trees — y’know, the type of tree known for their big, leafy appendages — turn orange, red, yellow, and brown, eventually shedding their leaves all together, is simple: It’s what the tree needs to do to stay alive during the coming months of winter. The long version has everything to do with what might be the only thing you remember from your middle school science class — photosynthesis, or the process by which plants turn carbon dioxide, water, and sunlight into sugars and oxygen (that is, plant food). Here, follow along with me here, then scroll down to the bottom to watch the whole video yourself:

Where Do Leaves Get Their Colors From in the First Place?

Photosynthesis depends on chlorophyll, the pigment that gives leaves their green color. But chlorophyll isn’t the only pigment found in leaves. These other pigments include carotenoids, which provide yellow, orange, and brown colors:

And anthocyanins, which bring shades of red and purple into the mix:

All of these pigments are important, but plants usually have the most chlorophyll; after all, photosynthesis is their primary job. They can’t survive without it — and neither can we, because of that whole needing-oxygen-to-breathe thing.

So What Happens When They Change from Color to Color?

In places that have dark, cold winters, plants get less sunlight — and as a result, deciduous trees that grow in these places tend to be less active during those periods. Since these trees don’t get enough sunlight during the winter to perform photosynthesis, it doesn’t really make a lot of sense for them to expend all this energy maintaining their leaves. So, when it starts to get colder and the days get shorter, the trees starting using their energy to keep the trunk and whatnot alive, instead of sending it to the leaves. Accordingly, the chlorophyll in the leaves breaks down, causing the green color to vanish and the other colors — which, you’ll recall, were already there, hiding out in the background — to take center stage. In truth, they’re not changing their color; they’re just loosing one particular shade. Then the leaves die, because again, there’s no need for them to be alive in the winter, and fall off.

Fun Fact:

The word “deciduous” comes from the Latin root meaning “to fall off.” TIL, right?

Check out the whole video below, and don’t forget to get outside and enjoy the last of the changing foliage. But hey, no worries if you live somewhere warm — you can still get in on all the cozy fall action, as long as you’re willing to get a little creative about it!

Images: VancityAllie/Flickr; SciShow/YouTube (5)