Studies were conducted to evaluate the effects of trinexapac-ethyl (TE) on height reduction, tillering, chlorophyll content, color, flowering, and root development of three ornamental grasses: Calamagrostis ×acutiflora 'Karl Foerster', Miscanthus sinensis 'Variegatus', and Pennisetum ×advena 'Rubrum'. Two applications of TE reduced height in all grasses and improved chlorophyll content in C. 'Karl Foerster' while delaying flowering in M. 'Variegatus' and P. 'Rubrum'. Tillering was slightly increased in M. 'Variegatus' with two TE applications. Shoot dry weight (SDW) and root dry weight (RDW) were reduced in C. 'Karl Foerster', SDW was reduced in P. 'Rubrum' and SDW and RDW were unaffected by applications of TE in M. 'Variegatus'. TE is effective for growth control in ornamental grass production systems; however, the results are species specific and should be tested further before widespread use on other ornamental grass species.