WordNet (r) 3.0 (2006):

heath aster
    n 1: common much-branched North American perennial with
         heathlike foliage and small starry white flowers [syn:
         heath aster, Aster ericoides]
    2: common North American perennial with heathlike foliage and
       small white flower heads [syn: heath aster, Aster
       arenosus]