2011 journal article
Flurprimidol pre-plant bulb soaks control growth of potted Liliums
Acta Horticulturae, 900, 79–87.
TL;DR:
Flurprimidol preplant bulb soaks for height control of ‘Star Gazer’ oriental lily, ‘Nellie White’ Easter lilies, and vigorously growing tiger lilies (Lilium lancifolium) were determined.
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In a series of experiments, flurprimidol (Topflor, SePRO Inc., Carmel, Indiana, USA) was applied as a preplant bulb soak to determine its efficacy on growth control of ‘Star Gazer’ oriental lily (Lilium hybrids), ‘Nellie White’ Easter lilies (Lilium longiflorum), and vigorously growing tiger lilies (Lilium lancifolium). Emergence date was noted, and the plants were measured at bloom for plant height, plant diameter, and flower number. Optimal concentrations varied by species. Preplant bulb soaks of flurprimidol at 25 to 400 mg L were applied to ‘Star Gazer’, and a concentration of 25 mg L resulted in plants 47.7 cm tall, which were 22.7% shorter than the untreated control. ‘Orange Tiger’ lily bulbs were hydrated in 17°C water for 1 h, allowed to drain 1 h, given 10-min soaks of 0 to 160 mg L flurprimidol, and then allowed to drain for 1 h prior to potting. Flurprimidol at 10 to 20 mg L controlled plant stretch. Plants were transplanted into a field, and no residual effect of flurprimidol preplant bulb soaks were found on the second year growth. Rates were confirmed with three additional L. lancifolium cultivars, and cultivar response varied with 10 to 20 mg L being effective for ‘Pink Tiger’ and ‘Yellow Tiger’ while 10 mg L was excessive for ‘White Tiger’. ‘Nellie White’ Easter lilies were more responsive to flurprimidol preplant bulb soaks than other lily cultivars. Optimal concentrations were in the range of 1 to 2 mg L flurprimidol for 9/10 sized bulbs. Not pre-soaking the bulbs in water or prolonged soaking (≥64 min) the bulbs in flurprimidol increased the plant growth regulator efficacy for ‘Nellie White’. INTRODUCTION Preplant bulb soaks using plant growth regulators have been shown to control lily height. Extensive research investigated the effectiveness of ancymidol as a preplant bulb soak (Lewis and Lewis, 1980; Wilkins and Grueber, 1983; Larson et al., 1987; Wulster et al., 1987). Ancymidol preplant bulb soaks were not adopted commercially because of inconsistent results (Larson et al., 1987). Uniconazole has an advantage over ancymidol due to higher activity at lower doses (Bailey and Miller, 1989a). Preplant uniconazole soaks to Asiatic hybrid lilies have been reported to be more effective than substrate drenches (Bearce and Singha, 1990). Uniconazole preplant bulb soaks of 0.25 to 10 mg L ranging from 1 to 30 min, with lower concentrations soaked for longer durations, were found to be effective in controlling excessive plant growth of Easter lilies (Bailey and Miller, 1989b) and hybrid lilies (Ranwala et al., 2002). Flurprimidol (Topflor, SePRO Corp., Carmel, Ind.) has been available in Europe for over 20 years as a 1.47% formulation and was introduced into the US market as a 0.38% formulation. At this time commercial dose recommendations for potted lilies are not available. Therefore, the objective of this research was to determine the efficacy of flurprimidol preplant bulb soaks for height control of ‘Star Gazer’ oriental lily (Lilium hybrids), ‘Nellie White’ Easter lilies (Lilium longiflorum), and vigorously growing tiger lilies (Lilium lancifolium). Proc. II IS on the Genus Lilium Eds.: A. Grassotti and G. Burchi Acta Hort. 900, ISHS 2011 80 MATERIALS AND METHODS ‘Star Gazer’ 1. Experiment 1. Cased cooled ‘Star Gazer’ oriental lily bulbs (12/14 cm) were potted, 2 bulbs per pot, in 15.2 cm (6 inch) diameter round plastic pots with a volume of 1.9 L (2.01 quarts) on 22 January 2003. The root substrate was Berger BM 6 (Berger Peat Moss, St. Modeste, Quebec, Canada). Plants were placed in a greenhouse under natural day lengths after potting with day/night temperature set points of 20.0/18.3°C (68/65°F). Plants were fertilized weekly with 150 mg L N using 15-0-15. On 22 January 2003, preplant bulb soaks (in mg L) were applied for 10 min: flurprimidol (0.38%) at 25, 50, 100, 200, or 400. An untreated control was also included. The experiment was a completely randomized design with six single plant replications of the 6 treatments. Emergence dates (for bulbs treated with soaks), anthesis date (one flower per plant fully opened), plant height at anthesis (measured from the soil line to the uppermost tip of the inflorescence), and number of buds on the stem with the first open flower were recorded. Lilium lancifolium 1. Experiment 2. Flurprimidol was applied to size 16/18 ‘Orange Tiger’ lilies (Lilium lancifolium) on 13 February 2009. Bulbs were hydrated in 17°C water for 1 h, allowed to drain 1 h, given 10-min soaks of 0, 5, 10, 20, 40, 80, or 160 mg L flurprimidol, and then allowed to drain for 1 h prior to potting. Bulbs were planted into 16.5 cm wide (2.72 L) pots containing Fafard 4P (Conrad Fafard, Inc., Agawam, MA). Plants were grown under a regime of 21.1°C days and 15.5°C nights. Plants were fertilized daily using 13-2-13 Cal-Mag at 150 mg L. The experiment was randomized with eight replications of each of the seven treatments. Data were collected on date of emergence, anthesis date, height at anthesis, and number of buds. All data were subjected to PROC GLM and PROC REG (SAS Inst., Cary, NC). Where the F test indicated evidence of significant difference among the means, LSD (P0.05) was used to establish differences between means. 2. Experiment 3. After the completion of Experiment 2, five plants treated with 0, 5, 10, 20, or 40 mg L flurprimidol were planted out in landscape beds on 23 June 2009 to evaluate the residual effects of flurprimidol. Plants were installed in a randomized block design and spaced at 45 cm centers apart. Plants were irrigated as needed. In 2010 data were collected on flowering date, height at flowering, shoot number, and number of buds. 3. Experiment 4. In 2010, the same first season (Experiment 1) growing procedures were used with the following modifications. Lilium lancifolium ‘Pink Tiger’, ‘White Tiger’ and ‘Yellow Tiger’ bulbs were treated with 0, 10, 20, and 40 mg L flurprimidol on 19 February. Lilium longiflorum ‘Nellie White’ Preplant Soaks 1. Experiment 5. Cased cooled ‘Nellie White’ Easter lily bulbs (9/10 cm) were used. On 13 December 2005, preplant bulb soaks of flurprimidol (0.38%) at 1.25, 2.5, 5, 7.5, 10, or 20 mg L were applied for 5 min. The bulbs were allowed to air dry overnight prior to potting. Untreated controls were also included. The bulbs were potted with one bulb per pot, in 15.2 cm diameter round plastic pots with a volume of 1.9 L (2.01 quarts) on 14 December 2005. The root substrate was Berger BM 6 (Berger Peat Moss, St. Modeste, Quebec, Canada), which contained (v/v) 75% to 80% Canadian sphagnum peat and 20% to 25% perlite. Plants were placed in a greenhouse under natural day lengths after potting with day/night temperature set points of 20.0/18.3°C. Plants were fertilized weekly with 150 mg L N using 15-0-15. The experiment was a completely randomized design with six single plant replications of the seven treatments. Emergence dates (for bulbs treated with soaks), anthesis date (one flower per plant fully opened), plant height at anthesis (measured from the soil line to the uppermost tip of the inflorescence), and number of buds on the stem with the first open flower were recorded.