Shade, generally speaking, can be dark, dreary and difficult to garden in. It’s hard enough finding a plant that requires not all that much sunlight, let alone one that has light coloring to its foliage. But these rare birds are essential to making a good shade garden truly great. Plants with white, silver, or even light green variegation brighten up the dimmest of spots and instantly get elevated to focal point status. Have you always thought your shade was lacking something? Chances are, it’s some variegation and this episode has plenty of options to pick from.   Expert testimony: Susan Calhoun, owner of Plantswoman Design in Bainbridge, Washington.