Reprinted from Proc. Fla. StateHort. Soc. 91: 220-222. 1978.

HEIGHT REGULATION OF POINSETTIA WITH AGROWTH RETARDANT INCORPORATED IN THE

SOIL MEDIUM1

Gary J. WilfretIFAS, University of Florida,

Agricultural Research & Education Center,5007 60th Street E, Bradenton, Florida 3350S

Additional index words:phorbia pulcherrima.

ancymidol, chlormequat, Eu-

Abstract. Multi-branched poinsettia 'Annette Hegg Supreme' plants grown in 15 cm pots were evaluated following treatment with a granular 0.01% formulation of ancymidol (A-Rest"n) incorporated in the soil medium. Comparisonswere made with ancymidol or chlormequat applied as a soildrench or foliar spray. Plant heights for the granular, drench,and spray applications of 0.5 mg ai ancymidol per pot were24.8, 25.7, and 35.0 cm, respectively, compared to 42.1cm for the untreated plants. Chlormequat applied as afoliar spray (2000 ppm) and a soil drench (3000 ppm) in 2applications produced plants 31.9 and 30.9 cm tall, respectively. Inflorescence diameter was reduced only by theancymidol drench treatment of 0.75 mg ai/pot and granulartreatment at 2.0 mg ai/pot.

Demand for potted poinsettias (Euphorbia pulcherrimaWilld.), a traditional symbol of the Christmas season, hasincreased national sales from 15.7 to 20 million pots from1976 to 1977 (10). Florida production has paralleled thisnational trend and 780 thousand potted poinsettias weresold in Florida in 1977 (10). Since the development of theself-branching 'Annette Hegg' and 'Mikkelsen' cultivars inthe 1960s (4), many growers plant a single cutting in a 15cm pot, selectively prune it to 5-6 nodes, and apply a growthregulator to maintain a plant:pot height ratio of 1.5 to 2.Chlormequat (2-chloroethyl trimethylammonium chloride),applied as a foliar spray or soil drench, is used most fre-quentlv (2, ?>). Ancvmidol (a-cyclopropyl-o;-(4-methoxy-phenvl)-5-pyrimidine) is useful as a soil drench but is noteffective as a foliar spray (1, 9). Both current applicationmethods of the growth retardant require an additionaloperation in the crop cycle. Attempts to eliminate thislabor-consuming step have included: 1) treating stock plantswith chlormequat (8): 2) soaking pots and propagationblocks in ancymidol (5, 12); and 3) applying chlormequatand ancvmidol through the irrigation system (6, 7). All ofthese methods either adversclv affected plant growth or required an impractical quantity of the chemical. A recentreport indicated that a granular formulation of ancymidolincorporated in the soil medium would properly maintainplant height of multi-branched poinsettias grown in 10 cmpots for 9 weeks (11).

This study was conducted to test the effectiveness of agranular formulation of ancymidol amended to the soilmedium in comparison with chlormequat and ancymidolfor height retardation of multi-branched poinsettias grownin 15 cm pots.

Materials and Methods

A 0.01% granular formulation of ancymidol was prepared by spraying the concentrate on finely ground clay(Florex 30/60).- The granular material was incorporatedinto the medium at concentration of 0, 0.25, 0.50, 0.75, 1.0,

BPI News - June, 1980

and 2.0 mg ai/pot. Each 15 cm diam pot contained 1200 cc,by volume, of a peat moss, vermiculite, sand, perlite (6:3:2:1,v/v) medium. Medium was amended with Osmocote(R>14-11.6-5.7, Osmocote(R) 18-2.6-10, ordinary superphosphate,dolomite, hydrated lime, and Perk<R>3 at 3.18, 4.95, 1.36,3.02, 1.13, and 1.13 kg/m3, respectively. Initial soil pH was6.2. A randomized design with 3 replications of 3 pots eachwas established and each experimental unit consisted of asingle cutting per plastic pot. Similar medium, without thegranular ancymidol, was prepared for comparison with ancymidol and chlormequat foliar sprays and soil drenches.Poinsettia 'Annette Hegg Supreme' cuttings, which wererooted in Oasis Rootcubes(R), were planted in the mediumon August 27, 1977 and were drenched with Truban(R) at2.5 g ai/1 in 150 ml aliquots. Plants were grown on a raisedbed in a polypropylene structure (30% shade) with naturalphotoperiod. Plants were pruned to 5 nodes on September16 and grown to maturity with min night temp of 18°Cand a max temp of 34°C. Pots were spaced on 38 cm centersand hand-irrigated as needed. Ancymidol at 0.50, 0.75, and1.0 mg ai/pot was applied to plants grown in mediumwithout the granular formulation on October 7 as eithera soil drench or as a foliar spray in 150 and 20 ml aliquotsper pot. respectively. Chlormequat was applied as a 2000ppm foliar spray in 20 ml aliquots or as a 3000 ppm soildrench in 150 ml aliquots on October 7 or October 7 and21. Plants were sprayed 'weekly for disease and in:control. Plant height above the pot rim, diameter of tireuppermost inflorescence, and number of bracts per inflorescence in color were recorded on December 12 and datawere analyzed statistically.

Results and Discussion

Plant response to the granular ancymidol was evidentwithin 3 weeks of planting (Fig. 1).Plants grown in mediumcontaining ancymidol were darker green and had shorterinternodes than the controls. No difference in total numberof internodes or premature development of axillary branchesprior to pruning was observed as a result ol the granularancvmidol.

Fig. 1. l.liiTl of granular ancymidol incorporated in medium at0, ().'_'.">. 0.50, and {).1j ni» ai/1") cm pot (from loft to light) 3 weeksafter planting established cuttings of poinsettia cv 'Annette Hegg Supreme.'

All growth regulators retarded elongation of the lateralbranches (Table 1). Only the single application of chlormequat as a soil drench failed to retard lateral shoot elongation. Since the most desirable plant height range for 15 cmpots is 23-20 cm above the pot rim. the control plants weretoo tall and not in proportion to the container. Incorporation ol the granular ancymidol at 0.50 and 0.75 mg ai/potproduced plants within the desired height range (Fig. 2).A difference in height of almost 10 cm was recorded between treatments of 0.25 and 0.5 mg ai/pot, with the latterapproaching the minimum plant height desirable in a 15cm pot. All ancymidol treatments applied as soil drenchesproduced plants from 21.1 to 26.1 cm tall and were notdifferent significantly from granular ancvmidol at 0.5 mgai/pot. Although ancymidol applied as a lobar spray retarded plant elongation, at none of the rates did it produceplants less than 30 cm tall.

Table 1. Effect of growth rclardant on plant height, inflorescencediameter, and number of color bracts of poinsettia cv. AnnetteHegg Supreme.'

\o.

Plant Bract coloredMg ai height diameter bracts

Treatment per pot (cm) (cm) Dec. 8

Control—water drench ._ 12.1 a' 26.8 abc 16.0 bedAncvmidol granular incorp. 0.25 31.5 b 20,1 a 17.8 abc

0.50 2I.S el 26.4 bed 17.7 abc0.75 23.2 ef 28.1 ab 18.1 ab1.0 18,1 Ig 25.0 bede 17.7 abc2.0 15.2 g 23.9 de 17.2 abed

Ancvmidol drench '" 150 ml 0.50 25.7 ct\c 26.5 bed 17.8 abc0.75 20.1 ede 2:i.5 e 16.0 bed1.(1 L'4.1 cf 25.3 ede 10,1 a

Ancvmidol spray '•' lit) ml 0.50 :;:>.<> i> L'0.7 abc lli.l bed

0.75 30.8 bed 20.5 bed 15.2 cd1.0 34.7 1) 21.1 ede 15.(1 bed

Chlormequat drench '" 150 mlOne application 510 .'ifj.O ah 21.5 cdr I 1.8 dI wo applications 1080 30.9 bed 2 1.2 ede 15.7 bed

Chlormequat spvav "* 20 mlOne application •10 34.1 b 25.7 bede 16.0 bedTwo applications 80 31.9 be 21.1 ede 15.0 cd

'Mean separation, within columns, by Duncan's multiple range test,5% level.

Fig. 2. Effect of granular ancymidol incorporated in mediumai 0, 0.25, 0.50. 1.0. and 2.0 mg ai/15 em pot (from left to right) ofpoinsettia cv. "Annette Hegg Supreme."

Diameter of the terminal inflorescence, which includedthe colored bracts, was significantly less only when ancymidol was applied as a granular material at 2.0 mg ai/potor as a soil drench at 6.75 mg ai/pot (Table 1). Duringdevelopment of the lateral branches following the manual

pruning, it was observed that bracts of plants grown inmedium containing granular ancymidol showed color priorto all other treatments. However, the number of coloredbracts per inflorescence on December 12 was not affectedby the treatments. Early development of the colored bractswould be advantageous to growers who produce plants forstore displays, starting in mid to late November.

All media were made in 50 pot lots in a cement mixerand a major concern was the even distribution among thepots of the relatively concentrated formulation of granularancymidol. Plant variability among pots containing specificconcentrations of a growth regulator was minimal, whichsuggested the chemicals were distributed uniformly. An additional observation during the final evaluation of theplants was that plants grown in medium containing > 1.0mg ai/pot of granular ancymidol produced lateral brancheswhich were more prostrate than upright. These laterals,if plants were handled roughly, were broken easily fromthe main stem.

Use of this formulation of ancymidol as an amendmentto the medium prior to planting would eliminate one laborconsuming step in the production of poinsettias and provide similar height control as present methods. Althoughthe major poinsettia cultivars should be evaluated at selected concentrations of this formulation, this study indicated that the maximum amount necessary for the production of 'Annette Hegg Supreme' is 0.5 mg ai/pot whena 0.01% granular formulation is utilized.

'Florida Agricultural Experiment Stations Journal Series No. 1434.-Provided bv Elanco Products. Fli Lilly &.- Co., Indianapolis, IN.•'Perk is a microelement mix manufactured by Kerr-McGee Corp.,

Jacksonville, FL.

Literature Cited

1. Bcscmer, S. T. 1072. Comparison of Quel and Cycocel for reducingheight ol two poinsettia cultivars—progress report. Flor. Rev. 150:.".7-:l8. 77.

L'. Cathey. II. M.. and R. L. Taylor. 1963. Growth control of poinsettias by use of cyclic lighting and (2-chlorocthvI) trimcthyl-ammonium chloride-. /. A nicy. Soc. Hoi I. Sci. 82:532-510.

3. Conover, C. A., and II. M. Vines. 1072. Chlormequat drench andspray applications to poinsettias. J. Amer. Soc. Hort. Sci. 97:316-320.

I. I-.cke. P.. Jr.. ed. 1976. I he Poinsettia Manual. Paul Fckc Poinsettiasi flic iniias. Calif.). 205 pp.

5. F.iiiert. A. I'.. 1070. Slow-release ancymidol for poinsettia by impregnation of clay pots. HortScience 11:374-375.

0. Furuta. I .. W. C. Jones. \\ . Humphrey, and T. Mock. 1071. Applying a growth rclardant through a container irrigation system. Calif.Agr. 28:9.

7. Holcomb. 1'. J., and J. W. White. 1970. A technique for soil application of a growth retardant. HortScience 5:10-17.

8. Larson. R. A., and M. I.. Mclntyre. 19G8. Residual effect of cycocelon poinsettia height control. J. Awcr. Soc. Hort. Sci. 93:667-672.

9. Tjia, 15., S. Ohpanayikool, and J. Buxton. 1976. Comparison of soilapplied growth regulators On height control of poinsettia. HortScience 11:373-374,

10. USDA. 1978. Floriculture Crops. Production area and sales, 1976and 1977; intentions for 1978. Crop Reporting Board, ESCS, SpCr6-1(78). 27 pp.

11. Wilfret, G. J., B. K. Harbaugh, and T. A. Nell. 1978. Heightcontrol of "Pixie" poinsettia with a granular formulation of ancvmidol. HortScience 13:356. (Abstr.).

12. W'itte. W. I ., and 15. Tjia. 1976. Effect of ancymidol impregnatedpropagation blocks on height of poinsettia. Proc. Fla. State Hort.Soc. 80:283-284.

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BPI News - June, 1980