Autumn. The weather may not know what time of year it is, but the trees surely do. Even a huge sugar maple, lounging quietly at the edge of the woods overlooking dry, beaten-down fields, is exhausted. Its leaves are dull and worn, riddled with the wounds of insect wars, mottled with faded yellows and edged with the brown of rot and desiccation. For this old maple there is no more growing to be done this year, not above ground at least.
The trees, the deciduous ones at least, know that it is time to begin to invest their gains, cut their losses and close up shop for the winter. Deciduous trees are like Europeans. Each year, they take an extended vacation at the most advantageous time of the year. It’s part of their nature, their heritage. They use the time to assess, regroup and renew themselves. Evergreens on the other hand, are more like Americans. Evergreens seek to eke out a living continuously, regardless of conditions, with less concern for such frivolities as taking time off. Figuratively, you would never see an evergreen wearing a tiny Speedo at the beach.
Spring seems such a long time ago. But one perfect night last spring, in response to some mysterious combination of increasing day length, the warming of the soil, and the jump-start of the hormone factory, the trees threw open their buds, and unfolded delicate leaves like the damp new wings of a butterfly. These wafer-thin leaves stretched between strong veins exposing thousands of square feet of tiny chloroplasts jammed with chlorophyll to the sun.
Chlorophyll is a complex and relatively unstable compound that is able to perform miracles with sunlight. But for all of chlorophyll’s complexity, its primary function is simply to use the sun’s energy to split open water molecules. In doing so, a cascading stream of hydrogen ions are liberated that rocket around like bowling balls setting a whole new series of sun-capturing reactions into motion. During the summer, chlorophyll is continuously used and must continuously be replaced. It’s rich green color dominates the lesser yellows, oranges and purples of other pigments. But in the fall, when the tree no longer needs to produce energy, the production of chlorophyll ceases, allowing the leaves to finally sport the dramatic fall colors of carotenes, xanthrophylls and other pigments laid bare by chlorophyll’s retreat.
In the fall, those tender young leaves that once provided precious surface area to capture the sun, now pose a liability, and expose thousands of square feet of surface area to the killing winds of winter. The deciduous tree makes the decision. It will rid itself of the leaves, but only after it withdraws all available energy sources back into its interior, deep into the tissues and roots, where it can be stored until it is needed next spring. To be ready for spring, the tree produces tiny buds that spend the winter exposed, like paupers with blankets pulled tightly around their shoulders. They turn their backs to the wind and the cold and hunker down like a small pack of hobos, huddled around a garbage can fire. They reduce their needs and try to outlast winter – the long, long winter - waiting for the day to again lengthen, the soil to warm, and the hormones to again flow.
And then on a perfect night in the spring, when it can wait no more, the tree relaxes. Stripping the blankets off the shoulders of its buds, it unfurls leaves like tiny flags and makes its charge – running screaming to the sun as naked as the day it was born.
