Winter dormancy. For a tree in our local climate we know that preparation for winter involves draining water from living tissues into intercellular spaces and transporting sugars into the roots for storage. Water loss from a cell has the effect of increasing the density of the cell sap and lowering its freezing point.

At extreme low temperatures, however, even water bound structurally to other molecules in the cell sap may be removed, resulting in irreversible cell damage.

During a winter I spent on the Great Plains years ago, I recall days, with temperatures 40 degrees below zero, when bark actually popped from cottonwood trees along White Clay Creek—during a month the Sioux call the “Moon of the Popping Trees.”

Closer to home, skunk cabbage shoots in frozen swamps are reminders of the subtle biochemistry that keeps life stirring.