The Reason Leaves Turn Color And Fall During The Autumn Months

Autumn is my favorite time of year. Not only is it the season of holidays such as Halloween and Thanksgiving, but the weather finally allows for sweaters to be worn, and there are so many pumpkin spice products available.

But perhaps my favorite reason for loving autumn is the colors. All the leaves on the trees are changing and falling, and there is so much red, orange, and yellow to be seen. Plus, who doesn’t love stepping on a crunchy leaf?

But while we might happily take more pictures for the Gram during autumn, how many of us really know the reason why leaves turn color in autumn?

Well, as it turns out, science has the answer. According to IFL Science, throughout the majority of the year, leaves are green. The reason for that is what is called chlorophyll. This pigment is used during the process of photosynthesis.

During this, chlorophyll absorbs the sunlight’s green and yellow wavelengths. However, it doesn’t absorb the green light, which gets reflected back. The chlorophyll pigment is what helps trees change carbon dioxide and water into sugars that nourish the tree. Pretty cool, right?

Well, during the autumn months, trees tend to slow down their photosynthesis process, meaning they take back many nutrients from their leaves as possible.

This drop in the photosynthesis process means that trees stop producing chlorophyll. Without the green color, the other natural pigments of a leaf are able to pop through, such as yellow flavonols and xanthophyll, as well as orange carotenoids.

Additionally, anthocyanins can also be produced by certain trees only in the fall months. These anthocyanins produce the red and even purple colors seen in some leaves. The anthocyanins are there to protect the leaves from sunlight once the tree’s chlorophyll is gone. Pretty cool, right?

And then the process begins again in the spring with the tree using stores of chlorophyll it absorbed from its leaves the previous autumn. Nature is such a beautiful and complex balance.

As for the falling of leaves, that is due to a hormone called auxin, which is produced by trees year round. As long as the hormone production remains stable, the leaves will stay connected to their tree. However, in autumn, the levels of auxin tend to go down, and as a result, this is what causes the tree’s leaves to fall away.

But while the leaves might have fallen, that doesn’t mean that they can’t be a viable part of the ecosystem as fallen leaves still contain tons of nutrients that can enrich the soil, as well as provide plenty of benefits for insects as well as the animals that eat the insects. It truly is incredible how ecosystems work.