For most of us, the sight of the leaves changing color is our annual signal that fall is officially here. There’s no doubt that seeing a sudden change in the color of the foliage surrounding our homes is exciting (and makes for excellent family photos). But if you’ve ever wondered why, exactly, the leaves go from green to orange (or yellow, or red), we’ve got the explanation. Here, we break down exactly why the leaves change color every fall.
Chlorophyll is what gives leaves their signature green color, but we’re guessing you might have known that. During spring and summer, the ample daylight gives plants plenty of time in the sun, and they produce chlorophyll regularly. Another thing you may recall from middle school science class: plants convert sunlight into energy in order to grow (yep, you got it—photosynthesis), which explains why the leaves appear more lush and green in the summer.
Once fall hits, daylight hours become shorter and plants get less sun as a result. Chlorophyll production slows down, which decreases the green pigment in the leaves. Other compounds present in the leaves, known as carotenoids and anthocyanins, are responsible for the changing colors that occur.
Carotenoids are found in bananas and carrots, and are responsible for creating yellow, orange, and brown colors. Anthocyanins are found in cherries and cranberries, and create bright, rich reds. Depending on the type of tree in question, more of one compound or the other might be present, which is why some leaves turn yellow, but others turn red. Temperature and soil conditions also play a part in the process.
Eventually, the leaves become dehydrated from the lack of sunlight (and photosynthesis) and fall into piles on lawns and streets everywhere. Whether you clear them out, let them decompose, or sweep them into another area, the entire process happens again and again every year.