Nature, behaving strangely

Here it is the beginning of the third quarter of the month of September, in the state of Maine, and all the leaves are still green. They are tired and worn out, a dull green, as opposed to the perky, full-of-promise lime green of early spring, or the serenely lush forest green of mid-summer, but still, green. Oh, there's the occasional patch of red or orange here and there, but it's very occasional. When we have a breezy day there are leaves all over the place, but they are dried-out, brown leaves that seem to have fallen from the trees without going through the mandatory color change first. Even the big, gorgeously round tree I pass every day on my way to work, that normally starts churning out the colored leaves in the middle of August, is still determinedly green, though many of its leaves are curling at the edges and turning brown.

A word to the wise: don't come leaf-peeping for a few weeks.

Has it been too dry? Is it because we still haven't had a frost? We have been having absolutely gorgeous weather for the past month -- sunny days, highs usually in the upper 60s, low humidity -- after a perfectly miserable June, when it rained or was overcast for all but three days, and July, during which if it wasn't raining it was the hot, humid weather that makes it so much hotter than whatever the thermometer declares it is. I have been enjoying these so much more cheerful and comfortable days as much as everyone else. People come into the library saying "isn't it a beautiful day?" and of course I agree. But I'm thinking, why aren't the leaves changing? And I wonder why no one else seems to have noticed.

I just checked online, and at scifun.chem.wisc.edu, on the Chemical of the Week page, learned that low temperatures destroy chlorophyll, which of course makes leaves green, and if those low temps. stay above freezing, it enhances anthocyanin (the red pigment found in some leaves) production. So maybe it has been too warm -- even at night the temperature has been dropping only into the lower 50s/ upper 40s (I can hear my Texas relatives, still enduring daily highs in the 90s, yelping "Upper 40s!") which may not be cool enough.

The information on this Chemical of the Week page says one thing that really confuses me: "bright sunlight also breaks down chlorophyll." But in that case, why are leaves so green during the summer? Admittedly, at the beginning of this summer, here in Maine, we didn't have that much "bright sunlight," but other places have lots of sunshine during their summers, and they still have green leaves.

But then, chemistry has always left me in the dark. I realize it's life at the most basic level -- that it isn't just biology as destiny, but chemistry as destiny -- but that just means life at the most basic level leaves me in the dark.

And why aren't the leaves changing?