Sunday, October 4, 2009


The sumac leaves have turned a deep red. The Virginia Creeper that twines around small trees and large trunks in the woods are just beginning to turn – one leaf red, one mottled, one still green. Autumn is here. The shorter days have shifted the chemical processes in deciduous trees and bushes to produce a hormone that weakens the cells at the point where the leaf attaches to the branch. The tree forms a layer of cells at that point to block off the circulation of water and nutrients between the roots and leaves. This layer of cells is called the abscission layer (abscission means to cut). Without the flow of water and nutrients, photosynthesis stops and no more chlorophyll is produced. As the chlorophyll breaks down, it changes from green to clear, letting the yellow, gold and red pigments that have always been present in the leaves shine through.

The abscission layer in the branch tips protects the little branches from rapid loss of water during the winter. The plants further protect themselves from winter by a process called hardening. Cells go dormant and the amount of sugar inside the cells increases. With more sugar inside the cells, the liquid freezes at a much lower temperature. It’s the same process that causes salt to melt the ice on our sidewalks because the freezing point of the water is lowered by the salt. Hardening allows plants in our part of the world to survive until spring.

Not all plants can do that. Yesterday I brought in a rosemary bush and my purple basil. They fill the house with wonderful scents and will survive (as long as I can keep them watered) away from the freezing days of winter.

Our sheep don’t have an abscission layer, but they do add layers to keep them warmer. They’ve been growing wool since late February, and many of them have fleeces four inches long or more. Wool is such a good insulator, they stay warm even in the drenching rains of the last few days. I only worry about sheep and warmth when we have ice storms and immediately after shearing. Even in those situations, the animals do pretty well. Sheep lay on extra calories to use during the winter as a layer of fat all around their bodies. The fat will be burned if their bodies need extra calories for warmth or to nourish a fetus or three, but until that time, it also acts as an insulating layer against the cold.

Dave and I, their shepherds are not nearly so well designed. I suppose we could eat on an extra layer of fat for ourselves, but I doubt very much if that layer would be burned away by spring. Instead we layer on clothes. This week I have shifted to long sleeved shirts and hooded sweatshirts. Yesterday when I left home I realized that I should have worn a crew neck shirt instead of a v-neck shirt. It won’t be long before we add long underwear bottoms and turtle neck shirts to our layering. And that’s just in the house. In another month, I’ll have my Thinsulate jacket on and my down coat out of the dry cleaner’s bag. Winter is coming.

Every spring I look back on autumn and marvel that I needed a coat for forty degree weather. Come April, we’ll strip off coats, hats, mittens and scarves and run around in our shirtsleeves at temperatures well below room temp. But for now, as the nights grow longer and the leaves turn from green to gold, we join the trees and the sheep in using layers to protect us from the cold.

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