Autumn is a beautiful time of year. The heat begins to fade, and leaves on the trees start to turn from green to red, orange, yellow, or even purple. Being outside in the crisp air is a pleasant change from the humidity we’ve had all throughout the summer. But as you rake your yard and create piles of multicolored leaves (that your kids will most likely jump in, starting the raking process all over again), have you ever wondered why they fall off in the first place?

Why Do Leaves Change Color?

There are a few things that get set in motion when the weather cools down. Did you know that trees can tell when the light changes and it begins to get darker earlier in the afternoons? They know winter is coming. That means doing some serious preparation; as the days get shorter, trees will gradually stop the process of photosynthesis. With less sunlight and harsher conditions, trees will pull in all their chlorophyll and store it in the main sturdy sections of the tree, like the trunk. As the chlorophyll is pulled out of the leaves, the green color will fade and other pigments (known as carotenoids) that are already present will be revealed; this is where the red, orange and yellow come from.

Why Do Leaves Fall From the Trees?

Not only do the leaves change color, but they also begin to fall from the tree. What makes this happen? Each leaf is connected to the twig or the trunk by an abscission layer. As the tree notices the light change, it will begin to cut off this layer where water and nutrients enter from the leaves to the main segment of the tree. Once this layer is completely shut off as the tree closes itself for the winter months, the leaves will naturally disconnect and fall from the tree.

Now you know why these changes happen when Autumn comes around.