WordNet (r) 3.0 (2006):

rock garden
    n 1: a garden featuring rocks; usually alpine plants [syn: rock
         garden, rockery]

Moby Thesaurus II by Grady Ward, 1.0:

31 Moby Thesaurus words for "rock garden":
   Japanese garden, alpine garden, arboretum, bed, bog garden, border,
   botanical garden, dry garden, flower bed, flower garden, garden,
   garden spot, grape ranch, grapery, herbarium, hortus siccus,
   jardin, kitchen garden, market garden, ornamental garden, paradise,
   pinetum, roof garden, shrubbery, sunken garden, tea garden,
   truck garden, vegetable garden, victory garden, vinery, vineyard