Tender plants may be removed entirely and potted for the coldest months. Harris and her husband, Wade, lug a couple of the troughs to their root cellar, where the troughs stay in the dark, just above freezing, until spring. Troughs with the hardiest plants may stay in place or be set on the ground with a light blanket of pine needles to protect them, or be shifted into a location where winter sun won't burn foliage. For pruning, Harris sometimes uses her hands, pulling off the tips of a dwarf variegated false cypress to shape the tips, and bonsai tools. For cleaning out old foliage in the plant's interior, she employs long-handled tweezers or the chopsticks, as Harris demonstrates on the interior of a dwarf Alberta spruce.
Many nurseries carry rock garden plants.
The North American Rock Garden Society quarterly bulletins have information about rock garden plants, and the group sponsors a yearly seed exchange. For information, contact the executive secretary, North American Rock Garden Society, P.O. Box 67, Millwood, N.Y. 10546. 1994 bulletin was devoted to trough gardening, including information on how to make a trough. A limited supply of copies is available. Detroit Free Press and may not be republished without permission.