Easter lilies are an important flowering potted crop in the United States with a wholesale value over $26.8 million for the 15 largest-producing states in 2010 (U.S. Department of Agriculture, 2011). Plant height can reach up to 1 m and must be controlled to produce plants for aesthetic value that are also amenable to packing, shipping, and retailing (Miller, 1992, 1993).
Easter lily height control may be achieved environmentally or culturally by manipulating the difference between the day and night air temperature, increasing light, enhancing plant spacing, minimizing exposure to far-red light, or using cold water in overhead irrigation (Blom et al., 1995, 2004; Erwin et al., 1989). However, chemical PGR applications may be used to produce compact potted easter lilies (McAvoy, 2001). Though foliar sprays and bulb dips are effective PGR application methods for bulb crops, substrate drenches provide more uniform height control over a longer duration (Boldt, 2008; Gent and McAvoy, 2000). Substrate drenches containing ancymidol, paclobutrazol, or uniconazole have been shown to successfully control easter lily height (Bailey and Miller, 1989; Gianfagna and Wulster, 1986; Jiao et al., 1986, 1990; Larson et al., 1987; Sanderson et al., 1975; Wilfret, 1987; Wilfret and Reiser, 1996).
Flurprimidol (Topflor; SePRO Corp., Carmel, IN) is available in the U.S. market as a 0.38% liquid formulation. In addition to ancymidol, paclobutrazol, and uniconazole, flurprimidol inhibits the conversion of ent-kaurene into ent-kaurenoic acid in the gibberellin biosynthesis pathway (Rademacher, 2000) and is active when applied as a foliar spray, bulb dip, and substrate drench (Currey and Lopez, 2010). Flurprimidol substrate drenches effectively suppressed the height of bulb crops such as tulip [Tulipa gesneriana (Krug et al., 2005b)], narcissus [Narcissus pseudonarcissus (Krug et al., 2006)], and lilies including Asiatic lily (Lilium ×asiatica), oriental lily (L. auratum × L. speciosum), and tiger lily (L. lancifolium) (Krug et al., 2005a; Pobudkiewicz and Nowak, 1992; Pobudkiewicz and Treder, 2006). While flurprimidol has been shown to have height-suppressing activity on easter lily when applied as a foliar spray (Whipker, 2004) and bulb dips (Whipker et al., 2011), we have found no reports of using flurprimidol substrate drenches to control height of easter lilies. Therefore, the objective of this research was to quantify how flurprimidol substrate drenches applied to ‘Nellie White’ easter lilies affect height at flowering, time to flowering, and flower number.
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