Why do Leaves Change Colors in the Fall?

Fall color at Devil's Lake State Park

I went on a hike at Devil's Lake State Park the other day as a stress reliever, but I also knew that it was the peak time for fall colors in central Wisconsin... and boy was there a colorful palette across the Baraboo hills! It was one of the most beautiful drives and hike I've ever taken. Many of you probably wonder driving by on a autumn day why would trees change such striking colors? Amazingly, scientists still cannot fully answer that question, but some of the factors have to do with weather throughout the growing season and day length.

Red Maple leaves

As you know, nearly all plants contain the pigment Chlorophyll. This is what makes the leafs green and helps the plant take in energy from the sun to aid in photosynthesis which is how the plant makes food (with the added components of water and oxygen in the equation too). with the coming of fall, the length if nights becomes longer, and this triggers a biochemical change within the leaves. This is a sign for the tree to seize photosynthesis, stop producing and destroys the Chlorophyll in the leaves. As a result, other pigments in the leaves are revealed like Anthocyanin (gives the leaves a deep red color) and Carotenoids (gives the orange and yellow colors). After that, the tree goes through senescence or detaching of the petiole (leaf stalk) from the node.
Weather also plays a role. The key ingredient is warm, sunny days and crisp, but not freezing nights. This mixture specifically produces the striking reds in leaves. Also, intense colors also need a warm spring, normal summer, and adequate moisture throughout the growing season. This year, Wisconsin had a warm spring, wet and warm summer, and cool nights in the fall... the perfect combination for fall colors! And now you've learned something today.

Smooth Sumac leaflets

What's astonishes me is that the tree knows. Think about it, here is an organism that has no brain or central nervous system, and yet it goes through this whole thing because it "knows" that winter is coming... this is a plant folks. It's events like this that made me realize that everything didn't happen by chance or accident. Something to think about when you're zoning out at class or work. Anyway, you can now enjoy the fall colors even more this autumn!

Verse of the day: "Above all else, guard your heart, for it is the wellspring of life." - Proverbs 4:23