The North American Rock Garden Society Alpine Plant Sale is the Botanic Gardens' undiscovered treasure. While hordes descend upon the gardens during the annual spring sale in May, the atmosphere is much calmer and more congenial during the Alpine Plant Sale just one month earlier, when gardeners come in search of unusual, hardy plants, such as spreading groundcovers, candytufts, succulents, skullcaps and mallows. Though society members get first pick, there are still plenty of hard-to-find species available when the doors open to the public. Can you dig it?