Pre-Plant Bulb Dips for Height Control in LA and Oriental Hybrid Lilies

Pre-Plant Bulb Dips for Height Control in LA and Oriental Hybrid Lilies W.B. Miller, A. Chang, G. Legnani, N. Patel, A.P. Ranwala, M. Reitmeier, S.S. Scholl, and B.B. Stewart Department of Horticulture Cornell University Ithaca NY 14853 Tel: 607-255-1799 Fax: 607-255-9998 E-mail: wbm8@cornell.edu Keywords: ancymidol, Lilium, paclobutrazole, plant growth regulators, uniconazole Abstract Height control is a crucial element for successful production of containerized lilies (Lilium sp.). While it has long been known that pre-plant dips in chemical Plant Growth Regulators (PGRs) can be effective for height control, new active ingredients, new cultivars, and new classes of lilies have necessitated a re-examination of this technique for height control. Advantages of pre-plant PGR dips are time and labor savings, accurate dosages, reasonable cost and perhaps most important, legality (at least in the United States). Disadvantages are that the treatment is applied well before there is a known height excess and questions of disposal of the used dip solution (environmental concerns). In this work, we investigated several commercial products (ancymidol, paclobutrazole and uniconazole) and a range of concentrations on the Oriental hybrid cultivars Aubade, Berlin, Sissi, Stargazer, Tom Pouce and Muscadet and the LA s Royal Perfume, Best Seller, Royal Dream, Aladdins Dazzle, Salmon Classic and Royal Parade. From these experiments, we have determined that 1) bulb dips, especially with paclobutrazole and uniconazole, can be a highly effective means of height control, 2) LA hybrid lilies are much more sensitive than Oriental hybrids and require lower rates, 3) care to not over-dose should be exercised in a commercial setting. INTRODUCTION In the United States, lilies are commonly forced as containerized (pot) plants. While dwarf lily cultivars are available that are well-suited to pot culture, the desire for new cultivars and new colors leads growers to choose cut flower cultivars for use as pot specimens. Therefore, it is critical for growers to reduce shoot growth so that the plant is in aesthetic proportion to the container (Sachs et al., 1976). Transportation is also an issue because shorter plants allow better volume utilization of a truck and therefore are more economical. The general preferred height of a lily in a 15 cm diameter container is ca. 52-55 cm, including the pot. Several methods are available including negative DIF (Erwin and Heins, 1990), photoperiod control/reduction of far red light (Blom, et al., 1995), and PGR s. In the case of PGR s, foliar sprays and substrate drenches are well-known techniques for application of the active ingredient. Interest in pre-plant bulb dips has been ongoing for many years. Most of the research that has been published on lily PGR dips has been done with Lilium longiflorum and ancymidol (Simmonds and Cumming, 1977, 1978; Lewis and Lewis, 1980, 1982; Larson et al., 1987; Lewis and Gilbertz, 1987), although others such as ethephon have also been evaluated (Simmonds and Cumming, 1977). Over the years a wide range of experimental approaches have been tried, with some treatments lasting as long as 12 hours (Simmonds and Cumming, 1977) or as little as 2 seconds (e.g. Lewis and Lewis, 1982). Little has been published on the effectiveness of uniconazole (Sumagic) and paclobutrazole (Bonzi) as pre-plant dips for hybrid lilies. The objective of this work was to Proc. 8th Int. Symp. on Flowerbulbs Eds. G. Littlejohn et al. Acta Hort. 570, ISHS 2002 351

evaluate a range of concentrations of uniconazole (Sumagic), paclobutrazole (Bonzi), and ancymidol (A-Rest) as pre-plant bulb dips on 6 LA and 6 oriental hybrid lily cultivars grown as pot plants. MATERIALS AND METHODS Lily bulbs for this work were held in the original packaging at 3-4ºC until used. The basic procedure was to immerse 5 bulbs for 1 minute in 1 L of the growth regulator solution. Previous experiments indicated very little growth difference between a 1 min or a 5 min. treatment. Fresh growth regulator solution was used for each cultivar x PGR combination. After dipping, bulbs were allowed to dry 3-5 hrs before planting in 15 cm pots using a commercial soil-less media (Metro mix 360). All oriental hybrid cultivars ( Aubade, Berlin, Sissi, Stargazer, Tom Pouce, Muscadet ) were treated on March 10. For LA cultivars Royal Perfume, Best Seller, Royal Dream and Aladdins Dazzle, the control, Bonzi and Sumagic treatments were done on 29 March and the A-Rest treatments on 2 April. For the LA s Salmon Classic and Royal Parade, all treatments were done on 2 April. The LA hybrid bulbs were, on average, sprouted to ca. 1.5-2 cm, with Royal Perfume sprouted to ca. 4.5 cm at the time of dipping; sprouts on oriental bulbs were <1 cm. After planting, plants were forced in an 18ºC (65F) night temperature greenhouse with day temperatures approximately 22ºC. Standard fertilization, insect control (imidacloprid) and other cultural practices were followed. No fungicides were used. Data were collected as follows: 1) weekly height (pot rim to top of plant), 2) dates of emergence and anthesis, 3) height at anthesis, 4) number of leaves, chlorotic leaves, buds, aborted buds. RESULTS Emergence Date Treatments did not affect the date shoots emerged from the substrate (data not shown). Flowering Date In some cultivars, the highest Bonzi and Sumagic treatments caused a slight delay in flowering, never more than 2-3 days. This would not be considered a major commercial problem. Number of Flower Buds, Aborted Buds, leaves, and Yellow/Chlorotic Leaves Overall, plant quality was good with all cultivars. There were few aborted buds, little lower leaf chlorosis, and no treatment effects were apparent. The number of buds and total number of leaves varied by cultivar, but PGR treatments had no major effect (data not shown). There was no difference seen between treatments in flower bud size of the size of open flowers. Height The three active ingredients used varied in their effectiveness as height control agents when applied as pre-plant dips. Ancymidol (A-Rest) was the least effective product within the concentrations (11 to 33 mg/l) used, and with many cultivars gave very little height reduction within this range (Tables 1 and 2). Both Bonzi and Sumagic were broadly effective for reducing height of all 12 cultivars. A notable exception is the LA Bestseller, where paclobutrazole (Bonzi) had little effect in the concentration ranges tested. On an absolute active ingredient basis, uniconazole (Sumagic) was most effective, causing height reductions of as much as 43% when used at 10 mg/l ( Aladdins Dazzle and Royal Dream ). While paclobutrazole was very effective with many cultivars, somewhat higher concentrations of active ingredient were required (Tables 1 and 2). In many cases, the level of height reduction seen by these products would be considered excessive, but it does point out the much more powerful effects the triazoles have on lilies compared to ancymidol. 352

Growth Patterns Striking differences existed in the growth patterns of oriental vs. LA-hybrid lilies. For example, Fig. 1 shows weekly crop height of the oriental Aubade which was typical of the oriental hybrid cultivars used. It is clear that the orientals exhibit a sustained, in some cases, increasing growth rate in the first part of the crop (in this case, the first 2/3 or 60 days), followed by a sharp plateau (last 1/3 of the crop) where little additional growth occurs. This plateau corresponds to a period somewhat after attainment of the visible bud stage. In contrast, the LAhybrids do not have a plateau growth pattern, and the plant continues to elongate until flowering, as typified by the cultivar Royal Dream (Figure 2). In general, effective PGR treatments appeared to reduce the slope of the crop height curve, as shown in Figure 1. DISCUSSION Optimum dip rates varied by cultivar, and by hybrid group. Cultivar variability is a difficulty with PGR dips, and each cultivar needs to be tested individually. While we don t have specific data per se, we were generally impressed with the uniformity of treatment effects within a given cultivar, and the uniformity was certainly within the range of commercial acceptability. In general, Oriental hybrid lilies require somewhat higher concentrations of active ingredient than do LA hybrids. Asiatic hybrid cultivars require the least of all, and in many cases are hyper sensitive to dips and were severely stunted by Sumagic or Bonzi (unpublished data). A main liability of pre-plant dips is still the obvious fact that they are applied well before the grower knows there is a height problem, although tall cultivars will probably always need growth regulation. Another effective strategy might be to use a low, partially effective dip treatment, then apply additional foliar sprays as the crop develops. In this way, a relatively longlasting dip effect can be modified with the additional, short term control of a foliar spray. ACKNOWLEDGEMENTS We are grateful to the Royal Dutch Wholesalers Association for Flowerbulbs and Nursery Stock, SePro, Inc., Uniroyal Chemical Company, and Valent USA for financial and materials support of this research and to the greenhouse staff of the Kenneth Post Laboratory for care of plant material. Literature Cited Blom, T.J., Tsujita, M.J. and Roberts, G.L. 1995. Far-red at end of day and reduced irradiance affect plant height of Easter and asiatic hybrid lilies. HortScience 30:1009-1012. Erwin, J.E. and Heins, R.D. 1990. Temperature effects on lily development rate and morphology from the visible bud stage until anthesis. J. Amer. Soc. Hort. Sci. 115:644-646 Larson, R.A., Thorne, C.B., Milks, R.R., Isenberg, Y.M. and Brisson, L.D. 1987. Use of ancymidol bulb dips to control stem elongation of Easter lilies grown in a pine bark medium. J. Amer. Soc. Hort. Sci. 112:773-777. Lewis, A.J. and Gilbertz, D.A. 1987. Hybrid lily response to various methods of ancymidol application. Acta Hortic. 205:237-240. Lewis, A.J. and Lewis, J.S. 1980. Response of Lilium longiflorum to ancymidol bulb-dips. Sci. Hortic. 13:93-97. Lewis, A.J. and Lewis, J.S. 1982. Height control of Lilium longiflorum Thunb. Ace using ancymidol bulb-dips. HortScience 17:336-337. Sachs, R.W., Kofranek, A.M. and Hackett, W.P. 1976. Evaluating new pot plant species. Flor. Rev. 159(4116):35-36, 80-84. Simmonds, J.A. and Cumming, B.G. 1977. Bulb-dip application of growth-regulating chemicals for inhibiting stem elongation of Enchantment and Harmony lilies. Sci. Hortic. 6:71-81. Simmonds, J.A. and Cumming, B.G. 1978. The interaction of a dormancy-breaking cold treatment, ancymidol, and ethephon in relation to stem elongation and flower production of Lilium cultivars. Sci. Hortic. 8:57-64. 353

Tables Table 1. Height of six LA-hybrid lily cultivars at flowering. Bulbs were dipped for 1 min. in the growth regulator solutions indicated prior to planting. All bulbs were 14/16 cm, except Bestseller at 12/14 cm. Aladdin's Royal Royal Royal Salmon Dazzle Bestseller Dream Parade Perfume Classic Control 80.3 a 70.6 a 52.8 a 58.9 a 68.4 a 60.8 a Bonzi 50 mg/l 77.4 ab 64.6 bcd 53.8 a 52.4 bc 51.4cd 60.0 ab 100 mg/l 75.3 abc 69.6 abc 47.0 b 48.3 c 47.2 de 59.0 ab 200 mg/l 58.4 e 67.2 abcd 44.2 bc 42.3 d 42.2 efg 57.8 ab 300 mg/l 63.2 de 61.8 de 34.6 de 36.2 e 38.6 fgh 56.8 ab Sumagic 2.5 mg/l 46.2 f 58.6 e 39.6 cd 36.2 e 43.0 ef 54.0 bc 5.0 mg/l 39.8 gh 45.8 f 28.2 f 34.2 ef 36.4 ghi 48.4 c 7.5 mg/l 45.2 fg 43.6 f 31.2 ef 29.2 f 35.8 hi 40.8 d 10.0 mg/l 34.2 h 42.2 f 22.4 g 29.9 f 32.3 i 38.0 d A-Rest 11 mg/l 77.3 ab 70.0 ab 48.9 ab 54.0 ab 59.0 b 61.8 a 22 mg/l 69.4 cd 63.8 cde 47.0 b 54.0 ab 51.8 cd 60.6 ab 33 mg/l 76.0 bc 62.5 de 45.8 b 53.4 bc 55.4 bc 59.0 ab Values are means of 5 plants per treatment. Letters indicate mean separation in columns by Least Significant Difference (P 0.05) 354

Table 2. Height of six oriental hybrid lily cultivars at flowering. Bulbs were dipped for 1 min. in the growth regulator solutions indicated prior to planting. Bulbs of Berlin and Stargazer were 14/16 cm, all others were 16/18 cm. Tom Aubade Berlin Muscadet Sissi Stargazer Pouce Control 67.4 a 74.5 ab 62.6 abcd 72.0 a 67.0 a 61.0 a Bonzi 50 mg/l 60.2 b 77.6 a 63.4 abcd 61.6 bcde 58.6 bcde 54.6 b 100mg/L 47.2 c 63.8 bcd 63.4 abcd 58.6 cde 65.0 abc 48.6 cd 200 mg/l 30.8 e 56.2 cd 58.4 de 57.2def 44.2 fg 40.0 e 300 mg/l 24.4 e 43.6 e 54.4 ef 45.4 g 43.8 g 33.6 f Sumagic 2.5 mg/l 49.6 c 74.4 ab 60.4 bcd 65.8 abc 60.6abcd 47.8 d 5.0 mg/l 43.2 cd 65.6 bc 59.2 cde 55.8 def 58.0 cde 39.8 e 7.5 mg/l 40.2 d 64.8 bc 62.0 abcd 54.2 ef 54.0 de 37.0 ef 10.0 mg/l 38.5 d 52.4 de 52.2 f 50.0 fg 51.6 ef 38.2 ef A-Rest 11 mg/l 63.6 ab 70.8 ab 66.2 a 70.0 ab 64.0 abc 55.8 ab 22 mg/l 60.8 b 77.8 a 65.8 ab 67.0 abc 66.4 ab 52.4 bcd 33 mg/l 62.4 ab 69.3 ab 64.4 abc 63.2 bcd 64.2 abc 54.2 bc Values are means of 5 plants per treatment. Letters indicate mean separation in columns by Least Significant Difference (P 0.05) 355

Figurese 70 60 Plant Height (cm) 50 40 30 20 10 0 10 20 30 40 50 60 70 80 90 100 Day after planting Control Bonzi - 50 Bonzi - 100 Bonzi - 200 Bonzi - 300 Sumagic - 2.5 Sumagic - 5.0 Sumagic - 7.5 Sumagic - 10 A-Rest - 11 A-Rest - 22 A-Rest - 33 Fig. 1. Growth patterns of the oriental hybrid lily Aubade after dipping for 1 minute in the indicated growth regulators prior to planting. Flowering occurred on days 90-92. 356

60 50 40 Height (cm) 30 20 10 0 30 35 40 45 50 55 60 65 70 Day after planting Control Bonzi - 50 Bonzi - 100 Bonzi - 200 Bonzi - 300 Sumagic - 2.5 Sumagic - 5.0 Sumagic - 7.5 Sumagic - 10 A-Rest - 11 A-Rest - 22 A-Rest - 33 Fig. 2. Growth patterns of the LA-hybrid Royal Dream after dipping for 1 minute in the indicated growth regulators prior to planting. Flowering occurred on days 62-65. 357