We’ve just set our clocks back, but nature keeps her own time. It’s easy to read that her clock is ticking towards winter. Most of the deciduous trees on the Bent Twig Trail were decked out in autumn colors just last week, but many of these same trees have lost most of their leaves within the last week, and the pawpaw and spicebush trees look ready to let go of theirs any day.
A few years ago, I heard a piece on NPR by Robert Krulwich explaining that a layer of cells forms at the base of the leaf stem or petiole on deciduous trees known as the abscission layer. The development of this abscission layer is triggered by the short and colder days that stimulate the production of a hormone. This hormone acts like a system of little messengers that travel from leaf to leaf. Since leaves are in the production business—producing the food for the tree, receiving this message is a bit like getting the “pink slip” that says your services are no longer needed.
Although the wind may carry the leaves away, they were actually pushed off the trees. You see, it’s risky and costly for deciduous trees to keep their leaves all winter. They risk losing valuable water and enormous amounts of energy should their leaves be killed or damaged by winter freezes, as they’ll have to expend the energy of growing new ones. A factory owner who keeps a large unproductive staff may find their factory operating in the red. Everything in nature has its own economic system of checks and balances. Evergreen trees have a different strategy for accounting and adapting to winter, but that’s a tale for another day. In the meantime, imagine how strange it would be if we celebrated this autumn season as push instead of fall. It might be more accurate, but not as poetic.
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