A study was conducted to compare the growth-retarding effects of paclobutrazol (Bonzi), uniconizole (XE-1019, Sumagic), and daminozide (B-Nine) on container-grown bedding plants. Seedlings of Begonia semperflorens ‘Olympia’, ‘Scarletta’, and ‘Vodka’, Catharanthus roseus ‘Little Bright Eye’, Impatiens sultani ‘Blitz Orange’, and Zinnia elegans ‘Yellow Marvel’ were treated with a paclobutrazol spray at 0.15, 0.3 or 0.45 mg ai/plant, or a drench of 0.15 mg ai/pot. Uniconizole was applied as a spray at 0.025, 0.05, or 0.075 mg ai/plant, or a drench of 0.025 mg ai/pot. The daminozide was applied only as a 5000 ppm spray. Paclobutrazol and uniconizole were very effective in controlling the height of begonia, catharanthus (vinca), and impatiens at relatively low rates compared to daminozide. The height of zinnia was controlled by daminozide, but not by the other compounds at the rates tested.

Growth regulators, growth retardants
begonia (Begonia semperflorens), vinca (Catharanthus roseus), impatiens (Impatiens sultani), zinna (Zinnia elegans)
(±)-(R*,R*)-β(4-chlorophenyl)methyl)-α-(1,1-dimethylethyl)-1H-1,2,4-triazole-l-ethanol, Bonzi, paclobutrazol, (E)-(p-chlorophenyl)-4,4-dimethyl-2-(1,2,4-triazol-1-yl)-1-penten-3-01, Sumagic, uniconizole; butanedioic acid mono(2,2-dimethylhydrazide), B-Nine, daminozide
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Author notes

The authors wish to thank Lancaster Farms Nursery, Inc., Suffolk, VA 23425 for contribution of growth regulator and plants used in this study.

2Associate Professor and Agricultural Research Scientist, resp.

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1988