The Collaborative International Dictionary of English v.0.48:

Topiarian \Top`i*a"ri*an\, a. [See Toplary.]
   Of or pertaining to the ornamental cutting and trimming of
   trees, hedges, etc.; practicing ornamental gardening. [R.]
   "The topiarian artist." --Sir W. Scott.
   [1913 Webster]

         All the pedantries of the topiarian art. --C. Kingsley.
   [1913 Webster]