Perennial Care

ONCE THE GROUND has frozen, cover all your perennials with protective mulch of compost or dry peat moss. In our region, where temperatures can dip into the -20°s (F) [-30°s (C)], we have found a technique that allows the tougher perennials, like alpines, to overwinter right in their pots. First, we cover the pots with Microfoam, a 1/2-inch (1-cm) thick white foam blanket with plastic backing on both sides. Then we scatter a thick layer (about 6 inches [15 cm]) of loose peat moss onto the blanket and put another layer of clear plastic on top. Microfoam is a commercial product not generally available to home gardeners, but by substituting several layers of white spun fabric like Remay, available at most garden centers, you can create the same effect.

Most containers don't have enough soil volume to insulate perennial roots from freezing when winter temperatures drop. Two or three weeks prior to freeze-up, transplant into the garden any perennials growing in all but large containers.