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Sunny Days, Cool Nights Bring Out the Best Color

October 11, 2018

The unrelenting gloom of the past week has dampened the glorious fall foliage across the northwoods, but predictions of sunshine on Friday will certainly bring out the shutterbugs.

And even in the mist and gloom, the fiery yellows and reds and oranges of the maples, poplars, oaks and more can be seen and appreciated.
So what puts color into the leaves?

According to Lee Reich, gardening columnist for the Associated Press, green, of course, is from chlorophyll, most welcome in spring and throughout summer, but not the concern now. A leaf has to keep making new chlorophyll in order to stay green, and shorter days, with the sun hanging lower in the sky, trigger leaves to stop producing it, unmasking other pigments lurking there.

The yellows and oranges were there, hidden by the green of chlorophyll. They come from carotenoid pigments, which help chlorophyll do its job of harvesting sunlight to convert into plant energy.

Tannins are another pigment, actually metabolic wastes, that are hidden earlier in the season by chlorophyll. They give the subdued browns of fall, notable in some oaks but also enriching the yellow of beeches.

Because leaves harbor carotenoids and tannins all summer long, nothing particular about autumn weather should either intensify or subdue their autumn show. The only glitch could be an early, hard freeze while leaves are still chock full of chlorophyll. In that case, cell workings come to a halt and you’re left with frozen green leaves that eventually drop without any color change, Reich said.

Autumn color also has its reds and purples, most evident in red and some sugar maples, Japanese maples, scarlet oak, sourwood and winged euonymous. Those reds and purples come from yet another pigment, anthocyanins.

Source:  Antigo Daily Journal, October 10, 2018 edition

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