Moment of Science: Fall Color

Nature’s fireworks are on full display across many parts of the country right now… and barely at all in others. Here’s a primer on the how and why behind your favorite fall color changes.

* Chlorophyll is in every green plant you see. It’s not the only ingredient in leaves, but it’s how they make food from sunlight through photosynthesis. More sunlight in the summer months means those leaves stay nice and green. Suddenly, here comes the fall chill — and less sunlight, too. A layer of cells cuts off leaf nutrients at the stem. The remaining chlorophyll is broken down, and eventually used up entirely before that leaf falls… but it’s what that lack of chlorophyll reveals that makes for those flashy forest scenes. There are other types of pigments in leaves:

1) Carotenoids are produced in plant cells during the growing season, same as chlorophyll. That’s what gives yellow and orange colors to those fall leaves, plus food like bananas, corn and… well, carrots. It’s right there in the name.

2) Anthocyanins are your red, blue and purple-hued natural features. They’re only made in leaves like sassafras or red maple during the fall, as they take advantage of excess sugars… but year-round they’re found in red apples, cherries, blueberries and the like. They’re also a good anti-inflammatory for us humans.

* Leaves change color while they’re still attached to the tree — and for good reason. The tree conserves and reabsorbs that energy. When things warm up again, the growing leaves can regenerate that broken-down chlorophyll — or for remaining leaves in fall, turn just a little greener for a last hurrah in the waning weeks of the season. Waning sunlight is inevitable — but local weather patterns play a major role in peak fall color. Your best bet lies with warm, dry and sunny days, coupled with cool and crisp nights — as long as it stays above freezing. Summer drought can also delay that peak by a few weeks.

* A final safety note if you’re going out leaf-peeping this weekend: At 40mph, it would take you about 80 feet to stop a car. Wet roads double that stopping distance… and wet leaf-covered roads are more than triple (about 250 ft). Hands on the wheel and eyes on the road — no matter how lovely that view off to the side.

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