Outdoor Classroom: Why exactly do fall leaves change color?

It’s official.  Fall has arrived in the northwest.  Not that we didn’t already have signs~ the sun setting earlier, cooler evenings. But today, the cloudless blue sky was quickly covered by a cloudy blanket. The wind whisked the mounting mass of leaves around the backyard in mini tornados. I even contemplated turning the heat on. The arrival of fall means the frenetic pace of the summer and readying the crew for school will slowly wind down. Checklists will be nearly completed.  A time to wonder and contemplation resurfaces. Get ready to field some questions. Like why do leaves change color?

After a summer’s worth of making energy, the photosynthesis machine slowly comes to a halt. Photosynthesis is the process of plants making energy, a sugar called glucose, from water and carbon dioxide (what we exhale). Chlorophyll gives leaves their green color, and helps photosynthesis occur along with sunlight. As the days grow shorter, the rate of photosynthesis decreases and the chlorophyll goes away.  What remains are colors that were always present, yellows or oranges, but which had been covered fall leafby the green chlorophyll. It’s a bit like combing paints to create different colors. Cool nights cause glucose trapped in leaves to turn reddish, like in maples.

Collect leaves around your backyard and see what array of colors you can find. I found a couple of different craft projects to check out.  Try making place mats from the collected leaves or creating a fall foliage bouquet.  Most of all take a moment to get out with the kids.

–Becca Cahall

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