What two words strike fear in the hearts of the most intrepid gardeners? Dry shade. That’s what Graham Rice thinks. Rice, author of “Planting the Dry Shade Garden: The Best Plants for the Toughest Spot in Your Garden” (2011, Timber Press), has perfected the art of planting lush, dry-shade gardens in several different hardiness zones. He understands why gardeners are reluctant to plant under trees or on the north side of their homes. Little sunlight, tree roots, lack of nutrients, no air circulation and dry soil make for inhospitable conditions.