The 2012 ASHS Annual Conference

Liners of sea marigold, Borrichia frutescens (L) DC, were potted into 2.3 L containers filled with pine bark based media and grown in greenhouse conditions.  Plants were drenched with five levels of paclobutrazol (0, 5, 10, 20, or 40  mg/pot a.i.) {(±)-(R*,R*)-β-[(4-Chlorophenyl)methyl]-α-(1,1-dimethylethyl)-IH-1,2,4-triazole-1-ethanol} or uniconazole (0, 0.5, 1,2, or 4  mg/pot a.i.) [(E)-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol- 1-yl)- 1-penten-3-ol].  In a separate experiment, plants in 2.3 L containers were treated with paclobutrazol (0, 50, 100, 200, or 400  mg∙L^-1 a.i.) , uniconazole (0, 25, 50, 100, or 200  mg∙L^-1 a.i.) or daminozide (0, 2500, 5000, 10000, or 20000  mg∙L^-1 a.i.) ([butanedioic acid mono (2,2-dimethylhydrazide)]) as spray applications. Both experiments were a completely randomized orthogonal contrast design. Growth measures included height, width, internode length, flower count, leaf dry mass, stem dry mass, root dry mass, leaf number, leaf area, and ornamental rating for both experiments. Compared to controls, drench applied paclobutrazol (40 mg/pot a.i.), drench applied uniconazole (4 mg/pot a.i.), and spray uniconazole (200 mg∙L^-1 a.i.) decreased shoot mass 53%, 27%, and 43%, respectively. Daminozide and spray applied paclobutrazol did not reduce shoot dry mass compared to controls. Only spray applied uniconazole affected specific leaf area (SLA = leaf area / leaf mass), increasing SLA 21% at 200 mg∙L^-1 a.i. Paclobutrazol applied as a drench (40 mg/pot a.i.) reduced height 55% and uniconazole applied as a drench (4 mg/pot a.i.) reduced height 36%.  Drench applied paclobutrazol had greater discrimination amongst treatment levels and greater height control than uniconazole. Spray applications at tested levels of plant growth regulators (PGR) did not result in height control.  In general, drench application of PGRs resulted in height control of B. frutescensand spray applied PGRs had minimal effect.