golden yellows now prevail

ash, elm, basswood, poplar, birch, cottonwood, aspen, sugar maple…now is the time for the yellow leaves. turns out, yellow is easy for leaves. because the yellow is there all the time, it just gets swamped by the chlorophyl. as the chlorophyl breaks down in autumn, the yellow that has always been there becomes visible. red, on the other hand, still has scientists mystified. we know how the leaves turn red (it’s something about anthocyanins and built up sugars). but we don’t know why! there are competing theories as two why leaves turn red, the leading explanation having to do with protecting the tree from sunburn at a vulnerable time. sounds pretty weak, right?  any botany students out there (Josie?)…here’s your thesis subject. you’re welcome.

assemblage of yellow fall leaves