Published in the six Nashoba Publishing papers on Wenesday, January 3, 2001
Some plants die when the temperature hits freezing; others have means of adaptation. How do the hardy plants live through the winter?
Plant cells have a lot of water in them, and can be ripped apart when it freezes. To avoid this, many move water out of the cells. Some plants simply reduce their total water content; others move the water into the space between the cells, where ice crystals do much less damage. For this to work, plants need the temperature to drop gradually.
Another way plants resist frost damage is with antifreeze. Kale and turnip greens, for example, taste better after the first frost because they convert starches in the cells to sugars, for their antifreeze properties. Winter rye makes several different proteins which bind to ice crystals preventing their growth.
A third mechanism for cold hardiness sounds like a popular kind of human dietary supplement: antioxidants. When plants are exposed to cold, theres more danger than just from ice crystals. In 1999 scientists reported to the Nordic Association of Agricultural Scientists in Iceland, that in plants under stress from cold, molecules of certain metals create free radical ions, which then wreak havoc by oxidation. A group of proteins which plants manufacture in the cold, called dehydrins, were discovered to neutralize these metals, preventing the oxidation.
Many plants simply abandon all their stems and leaves, and retreat to their roots for the duration. Top growth slowly dies. When its finally all brown, dried out, and brittle, it can be safely cut to the ground. Its always a temptation to cut it down before it gets so ugly, but I figure as long as theres any green left, there may be photosynthesis going on. The carbohydrates made from that get sent to the roots, which store it for the energy they need to survive the winter, and then in spring to put out new top growth.
Another kind of winter damage to plants comes from roots being torn and exposed in frost heaves. For plants which are marginally hardy, prevent this stress by laying down a two- to four-inch layer of loose, bulky organic material, after the ground is frozen. Leaves unfortunately tend to mat together and smother plants, but if you shred them they wont. The best materials for winter mulch are salt marsh hay (regular hay gives you crabgrass), and your discarded Christmas tree, or other evergreen boughs.
© Copyright 2001 Catherine Holmes Clark