Effects of Growing Season, Plant Stage of Development, and Substrate Drench Applications of Paclobutrazol as Compared to a Daminozide Standard on Growth and Flowering of Gerbera Daisy ‘Bright Red with Light Eye'1

Abstract

Abstract Paclobutrazol substrate drenches at 0, 1, 2, 3, or 4 ppm were compared to a 2,500 ppm daminozide foliar spray standard in two finishing seasons (fall 2015 and spring 2016) and at two application stages for plant size control and improved market quality of ‘Bright Red with Light Eye' Gerbera daisy (Gerbera jamesonii Hook. f. ‘Bright Red with Light Eye') in 12.7cm (5 in) pots. Stage 1 was when the majority of plants had roots to the bottom of the substrate, and stage 2 was 2 weeks later. A consumer preference survey assessed purchasing preference when plants had two or three open flowers. Plant size index, foliage height, peduncle length, flower diameter, and quality rating at first flower decreased linearly while days to first flower increased quadratically with increasing paclobutrazol concentration, regardless of stage or season. Paclobutrazol applications delayed flowering, and decreased flower diameter and flower and bud counts, but these differences were small and not considered of practical importance. Based on quality rating at first flower and survey results, a 1 or 2 ppm paclobutrazol drench produced the most marketable plants in fall, and 0, 1, 2, or 3 ppm produced the most marketable plants in spring. Index words: plant growth retardant, B-Nine, Bonzi, greenhouse production Chemicals used in this study: B-Nine (daminozide) [butanedioic acid mono (2,2- dimethylhydrazide)] and Bonzi (paclobutrazol) [(±)-(R*,R*)-β-[(4-Chlorophenyl)methyl]-α-(1,1- dimethylethyl)-lH-1,2,4-triazole-1-ethanol] Species used in this study: ‘Bright Red with Light Eye' Gerbera daisy (Gerbera jamesonii Hook. f. ‘Bright Red with Light Eye')