Pineapple lily, a South African flowering bulb, is grown for its showy, pineapple-shaped inflorescences. Traditionally grown as a specialty cut flower, recent interest in pineapple lily as a potted greenhouse crop is because of the same factors that make it an attractive cut flower crop, namely, a unique growth habit and long-lasting inflorescences. The inflorescences of pineapple lily are top-heavy and the scape has a tendency to bend, topple, or break during production or transport (De Hertogh and Le Nard, 1993). This phenomenon is most common and problematic in the large cultivars developed for cut flower production, which are the majority of commercially available pineapple lily cultivars. Unlike cut flowers, very tall stems are not desirable in potted ornamentals (Lee et al., 2015). Although high light intensity during production can modestly reduce leaf and inflorescence length in pineapple lily (Carlson, 2010; Luria et al., 2011), this is impractical in many climates and is unlikely to result in sufficient height control overall.
Anti-gibberellin PGRs are used to restrict stem elongation in a wide variety of floriculture crops. Flurprimidol and paclobutrazol reduce stem and scape elongation in tulip (Tulipa gesneriana), hyacinth (Hyacinthus orientalis), caladium (Caladium bicolor), narcissus (Narcissus pseudonarcissus), and calla lily (Zantedeschia aethiopica) when applied as substrate drenches (Beckman and Lukens, 1997; Miller, 2016; Tjia, 1987; Whipker et al., 2011). Carlson et al. (2015) found that early postemergence substrate drenches of flurprimidol or paclobutrazol caused a 40% reduction in scape length in the dwarf ‘Leia’ pineapple lily at application rates of 1- and 2-mg a.i. per pot, respectively. Filios and Miller (2013) reported similar reductions in scape length in ‘Innocence’ pineapple lily (tall pineapple lily parentage) treated with substrate drenches (per pot) of 2-mg flurprimidol or 8-mg paclobutrazol. Because of the variability in size among commercially available pineapple lily cultivars, different degrees of height control are likely to be desired by growers. As in other ornamental bulbs, pineapple lily responsiveness to commercial PGR active ingredients is likely to vary with application timing and cultivar. The objective of this experiment was to examine the effects of flurprimidol or paclobutrazol drench concentrations on growth of several pineapple lily cultivars originally developed for the cut flower market, when grown as potted plants.
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