VARIETAL RESPONSE OF LANDSCAPE ANNUALS TO GREENHOUSE-APPLIED TRIAZOLE GROWTH REGULATORS

Abstract

Seven to 9 cvs each of Begonia semperflorens, Tagetes erecta, T. patula, and Petunia hybrida (grandiflora and multiflora types) were sown into seedling trays. One to 3 weeks after transplanting to flats (75 cm3/cell), paclobutrazol (PB) was sprayed at concentrations of 10 (begonia), 60 (marigold) or 100 (petunia) mg liter-1 at a 200 ml m-2 rate. Uniconazole (UC) was applied at one-half the PB concentrations. Plant height was measured before planting in the field May 17 and monthly through July. Species were analyzed separately and generally, there were no cultivar by triazole interactions. During the greenhouse phase, the triazoles controlled height of both marigold species compared to control, but in July the PB and UC treated plants were 100 and 91%, respectively, of control plant height. Flowering was delayed up to 4 days for UC treated T. patula plants. Height of triazole-treated petunias was 60-67% of control height during the greenhouse phase and 84-95% after 2 months in the field. Begonia height was reduced by triazoles during both phases. After 2 months in the field, PB and UC treated begonias were 72 and 44%, respectively, of control plant height.