The Collaborative International Dictionary of English v.0.48:

Botanist \Bot"a*nist\, n. [Cf. F. botaniste.]
   One skilled in botany; one versed in the knowledge of plants.
   [1913 Webster]

WordNet (r) 3.0 (2006):

botanist
    n 1: a biologist specializing in the study of plants [syn:
         botanist, phytologist, plant scientist]