Greenhouse production of rosemary (Rosemarinus officinalis) as small potted Christmas-tree topiaries for holiday sales have become necessary for many companies marketing to large retail outlets. Topiaries must be sheared multiple times to obtain an acceptable Christmas-tree shape. Most production greenhouses use hand pruning shears or hand-held cordless grass shears to shape topiaries free hand or with the aid of a template. Crop size and uniformity can vary with these shearing methods. To create a more uniform rosemary Christmastree topiary for cultivar evaluations, a mechanical shearing device constructed from over-the-counter parts was developed at the University of Illinois. A detailed description of the design and construction of this mechanical shearing device is presented in this report.