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):

botanical
    adj 1: of or relating to plants or botany; "botanical garden"
           [syn: botanic, botanical]
    n 1: a drug made from part of a plant (as the bark or root or
         leaves)

Moby Thesaurus II by Grady Ward, 1.0:

30 Moby Thesaurus words for "botanical":
   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