Influence of Benzyladenine, Trinexapac-ethyl, or Uniconazole Applications on Height and Tillering of Six Ornamental Grasses

Abstract

Three ornamental grasses, each within the families Cyperaceae [leatherleaf sedge (Carex buchananii), ‘Frosted Curls’ sedge (Carex comans), and ‘Toffee Twist’ sedge (Carex flagellifera)] and Poaceae [‘Rosea’ pampas grass (Cortaderia selloana), ‘Gracillimus’ miscanthus (Miscanthus sinensis), and muhly grass (Muhlenbergia capillaris)], received two foliar sprays 2 weeks apart of benzyladenine (BA) at 500 or 1000 mg·L−1, trinexapac-ethyl (TE) at 220 mg·L−1, or uniconazole at 20 or 40 mg·L−1. The influence of these spray applications on plant height and tiller number was assessed 0, 2, 4, and 8 weeks after the initial treatment (WAIT). Benzyladenine applications did not suppress the height of leatherleaf sedge or ‘Gracillimus’ miscanthus, yet did suppress the height of the other ornamental grasses by <15% compared to the controls, depending on the concentration used and the time. Applications of BA increased tiller production only in ‘Toffee Twist’ sedge at 2 and 4 WAIT compared to the controls; however, at 8 WAIT, this increase was diminished. Depending on the species, uniconazole suppressed the height of the Cyperaceae grasses by 11% to 22% compared to the controls at 8 WAIT. In Poaceae species, uniconazole suppressed the height of only ‘Rosea’ pampas grass by up to 32% compared to the controls. Uniconazole applications did not increase the tillering of any ornamental grasses tested, except ‘Toffee Twist’ sedge at 8 WAIT. Within Cyperaceae, TE suppressed the height of only ‘Toffee Twist’ sedge compared to the controls, while TE effectively controlled the height of all Poaceae grasses. Based on the species and time, TE application elicited up to 37% height suppression compared to the controls of Poaceae grasses, while it did not influence the tiller number of any ornamental grasses in this study.