The Effects of Paclobutrazol on the Vegetative and Reproductive Traits of Pycnanthemum1

Pycnanthemum is a relatively new market introduction. Due to a lack of existing production procedures, growers may hesitate to work with the genus. Determining optimal plant growth regulator concentrations could make the plant more accessible. In the study, P. virginianum were drenched with 0, 0.5, 1, 2, 4, 8, and 16 mg a.i./pot of paclobutrazol (Bonzi®), while P. flexuosum were drenched with 0, 6, and 8 mg a.i./pot. The height, growth index, shoot dry weight, density, and inflorescence count were measured to compare growth between treatments. The height was controlled in all treatments except P. virginianum treated with 0.5 mg a.i./pot. The inflorescence count and growth index of P. virginianum increased at lower concentrations, while the shoot dry weight decreased at higher concentrations. Pycnanthemum virginianum plants treated with 8 mg a.i./pot had increased density (mg·cm −3 ) . The height, inflorescence count, and growth index of P. flexuosum decreased when treated with paclobutrazol. Treating P. flexuosum with 6 mg a.i./pot decreased shoot dry weight compared to nontreated plants, although the shoot dry weight was numerically higher when treated with 8 mg a.i./pot compared to 6 mg a.i./pot . Plant introductions can be daunting for growers if plants have no previous protocols for care. Providing information about Pycnanthemum production will enable more efficient production and faster distribution. Species used in this study: Virginia mountain mint, Pycnanthemum virginianum (L.); Appalachian mountain mint, Pycnanthemum flexuosum (Walt.). Chemicals used in this study: paclobutrazol (Bonzi®).