Leaves

Many leaves are still hanging on the trees and in the long thin afternoon light they glow, each tree standing in a matching pool of brilliant color. This year’s scarlets and lemon yellows have been some of the best I’ve ever seen, though I imagine I think that every year, and every year it is true. What an incredible gift.

I recently read one of my favorite essays by Henry David Thoreau, Autumnal Tints. This is an annual pleasure. His descriptions bring me right to his side, walking along with the naturalist and sharing his joy at the magnificent colors. However, I do take issue with his dismissal of the science behind nature’s wonders as somehow dry and without soul:

The physiologist says it [ripening of fruit] is "due to an increased absorption of oxygen." That is the scientific account of the matter, -- only a reassertion of the fact.But I am more interested in the rosy cheek than I am to know
what particular diet the maiden fed on.

Most students who pursue the botanical sciences do so out of awe for the natural world, awe that learning science only serves to deepen. Knowing that autumn’s brilliant color show results from the cessation of chlorophyll production doesn’t detract from my appreciation of the stunning array of pigments that remain. That knowledge makes the summer leaves more mysterious, as if they are concealing some delicious secret, waiting for the right time to favor us with a glimpse of their complexity beyond the cool green shade.

When the leaves hang on well into November the chances are good that we may experience that glorious phenomenon of a cold bright morning filled with leaves dropping almost simultaneously.

Under normal circumstances the base of each leaf has by now formed an abscission layer, a layer of thin walled cells that eventually break down through enzyme activity. When this layer is weakened the leaf will eventually drop from the tree. But if the weather cooperates with clear skies and a hard freeze the stage is set for a dramatic and sudden leaf fall. This probably results from moisture freezing in the abscission layer. The cells rupture when the sun warms and melts these ice crystals and suddenly a rainfall of leaves begins. This doesn’t happen every year but it is unforgettable, standing under a big tree, watching the leaves pile up around your feet.

Some trees prefer to keep their leaves through the winter. Pin oak leaves are an example of a mascescent leaf, one that withers without falling off. When walking by pin oak trees on a December night the scratching sound of the dry mahogany leaves in the wind hurries behind me like some winter wraith, conjuring up thoughts of a warm room and lamplight.

In Autumnal Tints Mr. Thoreau seems to express a mistrust of science, as if knowledge could somehow snatch away the mystery and wonder of the natural world. I submit that knowing some of the mechanisms of our natural miracles can’t help but foster more wonder. As we unravel one mystery two more are revealed, hinting that Mother Nature really does have the last word and is smiling all the while.