At home in the mountains: clear light and more fall color
I'll come back to fall color, but I was also struck by the crystalline light this afternoon.
It's so clear today (with no humidity) that the light broke through the dark tint on my glasses making me wish I'd worn a hat and the mountain ridges have sharp edges.
|kitchen view in late afternoon|
I noticed more dogwoods, sourwoods, and Virginia creeper have already turned bright scarlet today. I'm hoping after this cold snap, we'll have at least a flush of decent fall color after the long warm fall so far (NOT conducive to fall color). The remarkably high rainfall amounts we've had this year will affect different species differently, too.
A revisited topic from various previous blog posts, here's a fall color piece I revised for a neighbor newsletter a couple of years ago.
Sept. 24, 21016 (Natural Gardening)
Well, what are sisters for, after all, especially if she's a botanist and garden educator (I’m now a volunteer one)? I had some fun reviewing the details and look forward to seeing how it will play out this season, with the warm and dry conditions forecast for this fall.
Basically, our fall colors in the Eastern U.S. are revealed as chlorophyll production slows down, cued by the shortening days and lengthening nights. The interplay of pigments in leaves determines the fall colors of different species, with the temperature and moisture determining color intensities. As the chlorophyll (which provides the overriding green color of leaves) breaks down, the other pigments in the leaves become evident. The carotenoids produce the yellow and oranges and anthocyanins produce the purple and reds. Anthocyanins are actively produced as a reaction between sugars and proteins - in the watery vacuoles of leaf cells, and their colors are influenced by acidity. They start showing up as the chlorophyll breaks down, and corky deposits start blocking the downward flow of sugars between leaves and stems.
Different trees have different combinations of the basic pigments, and here in Eastern North America, we have the largest diversity of species of trees that exhibit fall color, so many of our natives are prized in Europe for fall color -- our sweet gums and tulip poplars for example.
Some of the trees that are shades of oranges, reds, and purples include the red, white, and scarlet oaks, persimmon, sassafras, dogwood, sweet gum, as well as the maples. Hickories, river birch, redbud, tulip poplar, and sycamore turn yellow and gold, although the last two frequently turn brown and drop leaves early in droughty years like this one.
Beech leaves also accumulate tannin, adding a bronze color to the underlying yellows. The fall weather plays a key factor in whether it's a particularly good year for color, especially in the reds and purples. Day and night temperature and general moisture levels are important. Warm sunny days (with lots of sugar production) with cool crisp nights produce the best reddish and purple colors – from the anthocyanin pigments - at the same time chlorophyll production is declining. These are the “best” fall color years for bright red and orange hues.
Yellows are fairly consistent from year to year, since the carotenoids aren’t so affected by weather variations. Overly dry weather will produce more brownish leaves and early leaf drop, with washed-out colors in general.
This one was at the botanical garden (South Carolina Botanical Garden) where I used to work.