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HORTSCIENCE 26(2):133-135. 1991. were soaked for 10 min in deion-

ized water, 500 ppm GA3, 0.5% or 1.0% paclobutrazol, or a combination of 500 ppm Paclobutrazol, Gibberellic Acid, and GA, and 0.5% or 1.0% paclobutrazol. The paclobutrazol concentrations were chosen on Size Affect Growth and the basis of preliminary experiments that in- dicated that 0.5% and 1.0’% solutions would Flowering of Zantedeschia result in an average uptake of 2 or 4 mg of paclobutrazol per rhizome, respectively. Brian E. Corr1 and Richard E. Widmer2 Rhizomes were planted the following day Department of Horticultural Science, University of Minnesota, St. Paul, (10 Oct. 1986) in 15-cm pots (1.15-liter) in a medium of 1 soil : 1 sand : 2 sphagnum MN 55108 peat (by volume). When shoots were 2 to 3 Additional index words. , lily, floriculture, flowering potted , cm long, one-half of the rhizomes from the growth regulators, , deionized water and the GA3 presoak treat- ments were treated with a soil drench of 4 Abstract. Growth and flowering of Zantedeschia elliottiana W. Wats. and Z. rehmannii mg paclobutrazol in 240 ml water per pot as Engl. were studied. Rhizomes of both species were produced either in a glasshouse or described by Tjia (1987b). Plants were grown outdoors in California. Plants grown from glasshouse-produced rhizomes flowered in an unshaded glasshouse with ambient within 90 days only when a preplant rhizome soak of 500 ppm GA, was applied. Control photoperiod (45° N latitude), at a minimum plants of both species flowered when grown from field-produced rhizomes, but a GA 3 of 20C with a daytime increase of up to 7C. preplant rhizome soak significantly increased the number of (spathe and ) Growth data were taken at 90 days after produced. Paclobutrazol, applied as a preplant rhizome soak or as a soil drench when planting. There were five replications per shoots were 2 to 3 cm long, significantly limited plant height of Z. rehmannii from treatment, with data analyzed as a two-way either source if not treated with GA,. Paclobutrazol and GA, treatments interacted 2 × 4 factorial analysis of variance, and significantly to affect height and number of flowers of Z. rehmannii grown from field- mean separation by Tukey’s HSD. produced rhizomes. Treatment with GA3 overcame the dwarfing effect of paclobutra- Field-produced rhizomes. Rhizomes of both zol, while paclobutrazol treatment limited production. Z. rehmannii rhizomes species were harvested in late Nov. 1986 by >6.5 cm in diameter produced more shoots and than smaller rhizomes, regard- a commercial California producer and stored less of GA3 treatment. Emergence, number of shoots, and number of leaves from Z. at » 8C until shipment on 4 Feb. 1987. Rhi- elliottiana were not significantly affected by the rhizome size-GA3 variable combina- zomes were treated on arrival, stored over- tion. Production of normal flowers was increased by GA3 treatment of all sizes of Z. night, then planted the following morning as rehmannii rhizomes except the smallest, with the most flowers being produced by plants described previously for glasshouse-grown from the largest rhizomes. Production of deformed flowers was greatest from rhizomes rhizomes. There were five replications per treated with 500 ppm GA3, with no deformed flowers on control plants. treatment, with data analyzed as previously described. The calla lily (Zantedeschia spp.) is pro- curved abnormally and spathes developed To determine if rhizome size influences duced and marketed as a cut flower and a abnormally or had additional appendages on the response to GA3, additional rhizomes from

flowering potted plant for its attractive plants that received GA3 as a foliar spray at California were graded by diameter (<2.5,

spathes, commonly referred to as flowers. 250, 500, or 1000 ppm. Application of GA3 2.5 to 4.4,4.5 to 6.5, and >6.5 cm), soaked

Critical factors for Zantedeschia as a potted to Achimenes longiflora increased the num- in O, 100, or 500 ppm GA3 for 10 min., floricultural crop include flower number, plant ber of deformed flowers without increasing planted on 15 Mar. 1987, and grown for 120 height, and shoot and number. the total number of flowers (Vlahos, 1985). days as described above. Because of a short- Maximal flower production- from Zante- When Zantedeschia are grown as flower- age of large rhizomes, the > 6.5-cm-diame- deschia elliottiana and Z. rehmannii was ob- ing potted plants, height control by appli- ter rhizomes were treated with only O and

tained by treatment with 500 ppm GA3 as a cation of a plant growth retardant may be 500 ppm GA3. Previous research has shown preplant rhizome soak (Corr and Widmer, necessary. Paclobutrazol effectively con- 500 ppm to be the optimal concentration for

1987). Tjia (1987a) reported that GA3 treat- trolled height, but ancymidol did not in the flower production for 6- to 7-cm-diameter ment may increase the number of deformed concentrations tested (Tjia, 1987b). rhizomes (Corr and Widmer, 1987). Data

flowers produced. Application of GA3 to Zantedeschia rhizomes are graded by di- were taken at first flower and 90 days post- Spathiphyllum induced flowering in plants ameter. We found no reports in the literature planting. Total flower production was re- that otherwise would not flower, but in- relating growth or flowering to rhizome size. corded at 120 days after planting. Flowers

florescence distortions were noted on GA3- In Colocasia, another of the Araceae, were categorized as normal (no abnormality treated plants (Henny, 1981). Peduncles larger rhizomes emerge more quickly, pro- of the spathe) or deformed (spathe incom- duce taller plants with more shoots, and yield plete, partially open, or crinkled). There were more than do smaller rhizomes (Lee et al., five replications per treatment, with data Received for publication 14 Aug. 1989. Scientific 1979). In the , control of flowering analyzed as a one-way completely random- Journal Series Paper no. 17,230, Minnesota Ag- of longiflorum is partially determined ized design, and mean separation by Tukey’s ricultural Experiment Station, Univ. of Minne- HSD. sota, St. Paul, MN 55108. We thank Brown by bulb size. Larger produce more Co., Capitola, Calif., and the New Zealand Calla leaves and flowers than smaller bulbs (Kohl, Glasshouse-produced rhizomes. Z. reh- Producers Assn. for donating the rhizomes used 1967). mannii, but not Z. elliottiana, treated with in this study. Portions of this research were funded The objectives of this study were to ex- paclobutrazol only were shorter than plants

by the American Floral Endowment and the New amine the effects and interactions of GA3 not treated with either paclobutrazol or GA3 Zealand Calla Producers Assn. The cost of pub- and paclobutrazol treatments and source and (control) at 90 days after planting (Table 1). lishing this paper was defrayed in part by the pay- size of rhizomes on growth and flowering of There was no significant effect of paclobu- ment of page charges. Under postal regulations, Zantedeschia, and to use the results to better trazol on total number of flowers (Table 1), this paper therefore must be hereby marked ad- understand the control of flowering. date of emergence, days from plant to first vertisement solely to indicate this fact. 1 flower, date of first flower, peduncle length, Graduate Research Assistant. Current address: Glasshouse-produced rhizomes. Zante - Univ. of Tennessee, Dept. of Ornamental Hor- deschia elliottiana and Z. rehmannii rhi- spathe length, spathe width, number of leaves ticulture and Landscape Design, Knoxville, TN zomes were harvested from plants grown at per rhizome, number of shoots per rhizome, 37901. 20C minimum, then held for 8 weeks at 22 or number of leaves per shoot for either spe- 2Professor Emeritus. ± 2C until preplant treatments were applied. cies (data not presented).

HORTSCIENCE , VOL. 26(2), FEBRUARY 1991 133 Table 1. Effect of 10-min 500-ppm GA3 preplant rhizome soak and paclobutrazol treatments on height and number of flowers of Zantedeschia elliottiana and Z. rehmannii 90 days after planting. Plant ht (cm) Flowers (no.) Plant ht (cm) Flowers (no.)

Paclobutrazol z Source of rhizomes (mg/rhizome) Glasshouse Field Glasshouse Field Glasshouse Field Glasshouse Field

zPaclobutrazol preplant rhizome soak or soil drench at shoot emergence. yNS, *, **, ***, F test nonsignificant or significant at P = 0.05, 0.01, or 0.001, respectively. xSignificance could not be calculated due to reduction of sample size by loss of plants to Erwinia soft rot.

Table 2. Effect of rhizome size and 10-min 100- or 500-ppm GA 3 rhizome preplant soak on growth and flowering of Zantedeschia elliottiana and Z. rehmannii.

Treatment of rhizomes with GA3 over- number of shoots, or number of leaves per treatment for Z. rehmannii (Table 1). Be- came the limitation of plant height caused by shoot (data not presented). cause of losses of Z. elliottiana to bacterial paclobutrazol (Table 1). The most profound Field-produced rhizomes. In contrast to soft rot (Erwinia sp. ), multiple comparison effect of GA3 treatment was the promotion results with glasshouse-produced rhizomes, statistics could not be calculated for number of flowering of glasshouse-produced rhi- all plants grown from field-produced rhi- of flowers produced for that species. Z. reh- zomes. Plants grown from untreated glass- zomes flowered, with or without GA3 treat- mannii produced significantly more flowers house-produced rhizomes flowered sparsely ment, although GA3 treatment increased when treated with GA3, while paclobutrazol or not at all during the 90-day growth period flower production (Table 1). All other results treatment significantly limited the number of (Table 1). Gibberellic acid treatment of rhi- were similar to those obtained with glass- flowers produced. Paclobutrazol also inter- zomes of either species did not significantly house-produced rhizomes. Paclobutrazol acted with GA3 treatment (Table 1). affect date of emergence, number of leaves, treatment significantly interacted with GA3 Rhizome size and gibberellin. Days to first

134 H ORTS CIENCE, VOL. 26(2), FEBRUARY 1991 flower tended to be fewer with larger Z. el- tween glasshouse- and field-produced rhi- nation with paclobutrazol to produce plants liottiarra rhizomes, although significantly so zomes can be explained simply by storage with an aesthetically pleasing shape and ad- only when comparing untreated rhizomes temperature difference. equate flower production.

<2.5 cm to GA3-treated rhizomes >6.5 cm Since all tested rhizome sizes flowered, (Table 2). Z. elliottiana spathe width was smaller sizes, which are less expensive, may Literature Cited greatest on plants grown from untreated rhi- be useful for commercial production. Sev- Corr, B.E. 1988. Factors influencing growth and zomes >6.5 cm and significantly smaller on eral smaller rhizomes planted in a single pot flowering of Zantedeschia elliottiana and Z. plants grown from rhizomes <2.5 cm, re- may be more profitable than a single larger rehmannii. .PhD Diss., Univ. of Minnesota, St. Paul. gardless of GA3 treatment (Table 2). Days rhizome for flowering potted-plant produc- to emergence, shoot and leaf number, height tion. The cost per flower produced, rather Corr, B.E. and R.E. Widmer. 1987. Gibberellic than cost per rhizome, needs to be consid- acid increases flower number in Zantedeschia at first flower, and number of flowers from elliottiana and Z. rehmannii. HortScience Z. elliottiana rhizomes were not significantly ered. 22:605-607. affected by rhizome size-GA3 treatment The increased production of misshapen Corr, B.E. and R.E. Widmer. 1988. The effect combinations (Table 2). flowers as a result of GA3 treatment agrees of rhizome storage on growth of Zantedeschia Shoots tended to emerge more quickly and with previous work (Tjia, 1987a). The large elliottiana and Z. rehmannii. HortScience have more shoots and leaves from Z. reh- increase in total flower production outweighs 23:1001-1002. mannii rhizomes >6.5 cm than from smaller the relatively small increase in deformed Henny, R.J. 1981. Promotion of flowering in Spa- thiphyllum ‘Mauna Loa’ with gibberellic acid. rhizomes, regardless of GA3 treatment (Ta- flowers. The increase in deformed flowers ble 2). Plants grown from rhizomes >6.5 cm was similar to the response of Achimenes to HortScience 16:554-555. flowered the most quickly, regardless of GA GA , although in Achimenes the number of Kohl, H.C. 1967. Correlation between rate of leaf 3 3 initiation and apex diameter of Lilium longiflo- treatment (Table 2). The shortest Z. reh- normal flowers was unchanged with GA3 ap- rum cv. Ace. HortScience 2:15–16. mannii plants at first flower were grown from plication (Vlahos, 1985). Lee, M.S., J.H. Lee, and S.O. Yu. 1979. Effect rhizomes <2.5 cm in diameter (Table 2). The results of these experiments are com- of seed age and weight on major charac- Production of normal flowers was increased patible with other data (Corr, 1988) that show ters in different local strains of tare, Colocasia

by GA3 treatment of Z. rehmannii rhizomes that flower initiation of GA3-treated rhi- antiquorum (Schott)(in Korean with English of all sizes except the smallest, with the most zomes occurs at the time of planting and summary). J. Korean Soc. Hort. Sci. 20:134- flowers produced from the largest rhizomes continues for » 4 to 6 days after planting. 141. (Table 2). Production of deformed flowers Paclobutrazol rhizome presoak appears to in- Tjia, B. 1987a. The acid test. Greenhouse Man- was greatest from rhizomes treated with 500 hibit the initiation that occurs after planting. ager 5:128-134. Paclobutrazol applied as a soil drench, » 4 Tjia, B. 1987b. Growth regulator effect on growth ppm GA3 less from rhizomes treated with and flowering of Zantedeschia rehmannii hyb. 100 ppm, and none from untreated rhizomes weeks after planting, had a lesser effect on HortScience 22:507-508. (Table 2). At 500 pm GA more deformed , flower production. Commercial producers of 3 Vlahos, J.C. 1985. Effects of GA3 and BA on two flowers were produced from smaller than from Zantedeschia as flowering potted plants may of Achimenes longiflora under two levels

larger Z. rehmannii rhizomes, although the wish to consider the use of GA3 in combi- of irradiance. Acta Hort. 167:225–235. difference was not significant (Table 2). Spathe width of Z. rehmannii was not sig-

nificantly affected by the rhizome size-GA3 treatment combination (Table 2). Our results confirm previous research (Tjia, 1987b) indicating that paclobutrazol pro- vides effective height control on Z. rehman- nii and Z. elliottiana. Paclobutrazol applied as a preplant rhizome soak was of equal or greater effectiveness than the-commercially recommended post-emergence drench for height control of Zantedeschia, but it de- creased flower production from field-pro- duced Z. rehmannii rhizomes (Table 1) by > 60%. The preplant soak maybe more cost- effective, however, since the cost of labor and plant growth regulator used likely would be lower. . Gibberellin treatment overcame an un- known block to flowering in plants grown from glasshouse-produced rhizomes. Pre- sumably, an environmental requirement was missing during the growth or storage of these plants, since none of the untreated plants produced flowers in the quantity expected. According to preliminary research, length of storage of Zantedeschia rhizomes can influ- ence days to flower and number of flowers produced per rhizome (Corr, 1988). Glass- house-produced rhizomes were stored for 8 weeks, which is sufficiently long to cause rapid vegetative growth (Corr and Widmer, 1988), but may not have been long enough to cause flowering within 90 days of plant- ing. We have noted no effect of rhizome storage temperature on subsequent flowering (Corr and Widmer, unpublished). Therefore, it is unlikely the difference in flowering be-

H ORTSCIENCE, VOL. 26(2), FEBRUARY 1991 135