In a 1999 experiment, Salvia x sylvestris ‘May Night’ and Scabiosa columbaria ‘Butterfly Blue’ were treated with the following plant growth retardants (PGRs) or PGR mixes: B-Nine (daminozide) at 5000 ppm (applied twice); B-Nine at 5000 ppm + Cycocel (chlormequat chloride) at 1500 ppm; Florel (ethephon) at 500 ppm (applied twice); B-Nine at 5000 ppm + Florel at 500 ppm; Sumagic (uniconazole) at 20 ppm; or B-Nine at 5000 ppm + Sumagic at 10 ppm. B-Nine effectively suppressed growth of salvia but not scabiosa, while Florel was effective on both salvia and scabiosa. However, Florel delayed flowering of both species by about 10 days. Sumagic at 20 ppm suppressed growth of scabiosa but not salvia. The PGR combination treatments, in general, were no more effective, and frequently less effective than the more effective PGR for a given species applied alone. In 2000 Florel was applied once to both salvia and scabiosa at 0, 250, 500, 750, and 1000 ppm. B-Nine (5000 ppm) was also applied to salvia, and Sumagic (20 ppm) was applied to scabiosa. Plant height of salvia was suppressed linearly with increasing Florel concentrations up to 42 days after treatment (DAT). Salvia also responded with a linear increase in inflorescence numbers at 32 and 42 DAT. Florel suppressed the height of scabiosa ‘Butterfly Blue’ linearly up to 52 DAT without affecting the initial number of inflorescences. When the first set of inflorescences was removed and a second set developed, there was a linear increase in inflorescence numbers with increasing concentrations of Florel.

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Author notes

The authors would like to thank Lancaster Farms Wholesale Nursery, Suffolk, VA, for providing plant material and financial support for this research.

2Associate Professor, Agricultural Research Specialist, and Research Assistant, respectively.