Height Control of Potted Aurelian and Tiger Lilies

Height control of potted Lilium lancifolium (Tiger lily) and L. × aurelianense (Aurelian lily) plants would improve their marketability in the garden center and extend their market season. Bulbs (16-18 cm) were treated with Concise (uniconazole) or Piccolo (paclobutrazol). Bulbs were dipped for one minute in a 0, 2, 4, 8, or 16 mg/L Concise solution or for 15 minutes in a 0, 5, 10, 20, or 40 mg/L Piccolo solution. Drenches were applied at 300 ml per 3.4-L pot when shoots had reached ~5 cm in height. Drench rates were 0, 1, 2, 4 or 8 mg/L Concise or 0, 5, 10, 20 or 40 mg/L Piccolo. Concise dips were more effective in reducing Tiger lily plant height than drenches, with dips resulting in a 52% height reduction at six weeks after potting (WAP). Final plant height at 9 WAP was reduced 37% by the 4 mg/L dip rate which was comparable to the growth reduction of the 8 mg/L drench application. In contrast, Piccolo drenches were more effective than dips in controlling Tiger lily plant height. Piccolo applied as 10 mg/L drenches resulted in a 23% reduction in plant height at 6 WAP while dip rates at 20 or 40 mg/L resulted in similar height control. These plants were of acceptable size for marketing as potted plants. Aurelian lilies were less responsive to Concise. The 16 mg/L dip reduced plant height 60% at 6 WAP, resulting in a 46% height reduction at flowering (11 WAP). Concise dip or drench rates between 4 and 8 mg/L resulted in moderate (~30%) height control at 6 WAP that did not persist through flowering. Piccolo had no significant effect on height of Aurelian lily. The treatments did not affect time to flowering, flower number or width of the first open flower in either crop. INTRODUCTION Production of lilies for the home landscape market continues to increase in the United States (Pilon, 2006). There also is interest among breeders and marketers of potted crops to produce more potted lilies, other than Easter lilies, for holiday markets (Wells, 2010). While research on production practices and the use of plant growth regulators (PGRs) is extensive on Asiatic and Oriental lilies (Miller et al., 2005; Krug and Whipker, 2004), less is known about height control during production of other landscape lilies. Spray applications of PGRs require multiple applications to achieve sufficient height control of most lilies (Pilon, 2006). Barnes et al. (2010) reported flurprimidol applied as a bulb dip effective in reducing plant height of Lilium lancifolium ‘Orange Tiger’. Height control of potted L. lancifolium (Tiger lily) and L. × aurelianense (Aurelian lily) plants would improve their marketability in the garden center and extend their market season. Our objective was to evaluate the PGRs, Concise (uniconazole) and Piccolo (paclobutrazol), applied as dips (bulb soaks) or drenches on growth control of containerized ‘Red Twinkle’ Tiger lily and ‘Pink Perfection’ Aurelian lily. MATERIALS AND METHODS Commercial bulbs (16/18 cm) were purchased from K. van Bourgondien & Sons, Inc. (Virginia Beach, Virginia, USA) on 3 March 2010. Concise (uniconazole) or Piccolo (paclobutrazol) (both Fine Americas, Inc., Walnut Creek, California, USA) was applied as a bulb dip prior to planting or as a drench when plants were about 5 cm tall. Bulbs were planted in 3.4-L plastic pots filled with a peatlite medium (Fafard 52, Conrad Proc. II IS on the Genus Lilium Eds.: A. Grassotti and G. Burchi Acta Hort. 900, ISHS 2011 134 Fafard, Inc., Agawam Mass., USA). Plants were watered as necessary to prevent stress and fertilized with each irrigation with 200 mg/L N using 20-10-20. Dips were applied by soaking unwashed bulbs in a solution of Concise at 0, 2, 4, 8 or 12 mg/L for 1 min or Piccolo at 0, 5, 10, 20, or 40 for 15 min. Bulbs were allowed to drain for 1 h, then returned to cold storage overnight. All bulbs were potted 11 March 2010 and placed in the greenhouse. Drenches were applied as 300 ml of PGR solution poured evenly over the surface of moist medium when the plants had reached a height of about 5 cm. Drench rates were: Concise at 0, 1, 2, 4, or 8 mg/L or Piccolo at 0, 5, 10, 20, or 40 mg/L. Drenches were applied to the Tiger lilies on 23 March and to Aurelian lilies on 26 March. Data collected included plant height, date of flowering and flower width when first flower was fully expanded. Each species and PGR was set up as an individual experiment with plants arranged in a completely randomized design with five single plant replications. Data were subjected to PROC-GLM and PROC REG within a species, chemical and application method.