Ornamental grasses have gained increasing popularity not only in the landscapes, but they have also become prominent components in mixed containers (Cameron, 2004). Ornamental grasses comprise plants within Poaceae (grass family) and monocotyledonous grass-like plants within several families, including Cyperaceae (the sedge family), Juncaceae (the rush family), Restionaceae (the restio family), and Typhacea (the cattail family) (Darke, 1999). Many ornamental grasses are tall and vigorous during greenhouse or nursery production, hence suppressing plant height is necessary. Controlling the height of ornamental grasses has multiple benefits, including avoiding container lodging, maintaining height proportional to the container to improve quality, and increasing transportation efficiency by accommodating the maximum number of containers per cart. Published information on height control of ornamental grasses using plant growth regulators (PGRs) is limited. Sellmer et al. (2001) reported that the height of pampas grass was controlled with substrate drenches of ancymidol, paclobutrazol, or uniconazole. The height of purple fountain grass (Pennisetum ×advena ‘Rubrum’) was controlled by spray applications of 50 mg·L−1 ancymidol or paclobutrazol, 6000 mg·L−1 chlormequat chloride, or 40 mg·L−1 uniconazole (Wang et al., 2000). Uniconazole is a very active PGR that is effective on a wide range of species (Barrett, 2001), including pampas grass (Sellmer et al., 2001) and purple fountain grass (Wang et al., 2000). Uniconazole is a preferred PGR for vigorous species such as lily (Lilium spp.) and chrysanthemum (Chrysanthemum ×morifolium) because it is effective at a 10- and 9-fold less concentration compared to paclobutrazol, respectively (Barrett, 2001). To our knowledge, the efficacy of uniconazole on height control of a wide range of vigorous ornamental grasses is unknown. Trinexapac-ethyl (TE) effectively controlled the height of several species of turfgrass (Fagerness and Penner, 1998; McCullough et al., 2007). However, the efficacy of TE on the height regulation of ornamental grasses remains unknown. Commercial growers are interested in research-based information on the efficacy of PGRs for the height control of ornamental grasses (D. Dagen, personal communication).
Crop production time for ornamental grasses consists of the time required for sufficient tiller production to fill containers. Therefore, promoting tillering by applications of PGRs can be of great significance. Additionally, increased tillering can improve propagule yield of ornamental grasses propagated by divisions. Benzyladenine (BA) promoted branching of many dicotyledonous species (Carpenter, 1975; Emongor et al., 2004; Latimer and Freeborn, 2008; Little, 1985; Padhye et al., 2008) and hosta (Hosta spp.), a monocotyledonous species (Keever, 1994), and TE applications increased tillering in turfgrasses (Erwin and Koski, 1998; Erwin et al., 2002). To our knowledge, there is no published information available on the influence of BA or TE on the tillering of ornamental grasses.
The objective of this study was to quantify the influence of foliar spray applications of BA, TE, or uniconazole on height control and tillering of ornamental grasses. For this study, we used three commercially important ornamental grasses, each within Cyperaceae (leatherleaf sedge, ‘Frosted Curls’ sedge, and ‘Toffee Twist’ sedge) and Poaceae (‘Rosea’ pampas grass, ‘Gracillimus’ miscanthus, and muhly grass).
Barrett, J. 2001 Mechanisms of action 32 41 Gaston M.L., Konjoian P.S., Kunkle L.A. & Wilt M.F. Tips on regulating growth of floriculture crops Ohio Florists' Assn. Serv Columbus, OH
Blanchard, M.G. & Runkle, E.S. 2007 Dipping bedding plant liners in paclobutrazol or uniconazole inhibits subsequent stem extension HortTechnology 17 178 182
Emongor, V.E., Mutunga, C.M.M. & Chweya, J.A. 2004 Effect of benzyladenine on growth and flower yield of chamomile plants Trop. Agr. 81 1 6
Erwin, E.H., Ok, C.H., Fresenburg, B.S. & Dunn, J.H. 2002 Trinexapac-ethyl restricts shoot growth and prolongs stand density of ‘Meyer’ zoysiagrass fairway under shade HortScience 37 502 505
Gardner, D.S. & Metzger, J.D. 2005 Use of the trinexapac-ethyl for growth regulation of chrysanthemum (Dendranthema ×grandiflora) HortScience 40 670 674
Fagerness, M.J. & Penner, D. 1998 Evaluation of V-10029 and trinexapac-ethyl for annual bluegrass seedhead suppression and growth regulation of five cool-season turfgrass species Weed Technol. 12 436 440
Li, A. & Liu, Z. 2003 Effects of benzyladenine and naphthalene acetic acid on growth and camptothecin accumulation in Camptotheca acuminate seedlings J. Plant Growth Regul. 22 205 216
Little, C.H.A. 1985 Increasing lateral shoot production in balsam fir Christmas trees with cytokinin application HortScience 20 713 714
McCullough, P.E., Liu, H., McCarty, L.B. & Toler, J.E. 2007 Trinexapac-ethyl application regimens influence growth, quality, and performance of bermudagrass and creeping bentgrass putting greens Crop Sci. 47 2138 2144
Sellmer, J.C., Adkins, C.R., McCall, I. & Whipker, B.E. 2001 Pampas grass responses to ancymidol, paclobutrazol, and uniconazole substrate drenches HortTechnology 11 216 219
Wang, S., Carlson, W., Gao, H., Cameron, A. & Heins, R.D. 2000 Cultivating purple fountain grass 104 105 Heins R.D., Cameron A. & Carlson W. Firing up perennials 2000 ed Meister Media Willoughby, OH