The Collaborative International Dictionary of English v.0.48:

Botanic \Bo*tan"ic\, Botanical \Bo*tan"ic*al\, a. [Cf. F.
   botanique. See Botany.]
   Of or pertaining to botany; relating to the study of plants;
   as, a botanical system, arrangement, textbook, expedition. --
   Bo*tan"ic*al*ly, adv.
   [1913 Webster]

   Botanic garden, a garden devoted to the culture of plants
      collected for the purpose of illustrating the science of
      botany.

   Botanic physician, a physician whose medicines consist
      chiefly of herbs and roots.
      [1913 Webster]

WordNet (r) 3.0 (2006):

botanic
    adj 1: of or relating to plants or botany; "botanical garden"
           [syn: botanic, botanical]

Moby Thesaurus II by Grady Ward, 1.0:

29 Moby Thesaurus words for "botanic":
   bulbous, cereal, farinaceous, fruitlike, fruity, herbaceous,
   herbal, herbose, herbous, herby, leguminose, leguminous,
   phytobiological, phytochemical, phytologic, plantlike, pomological,
   radicated, radiciform, radicular, rhizoid, rootlike, tuberous,
   vegetable, vegetal, vegetarian, vegetational, vegetative, weedy