‘Osaka White’ or ‘Nagoya Red’. A Kuehny et al. (1998) applied fo- Ornamental uniconazole foliar spray of 16 mg·L–1 liar sprays of ancymidol (∝-cyclopropyl- Cabbage and resulted in 17% shorter ‘Nagoya Red’ ∝-(p-methoxyphenyl)-5-pyrimidine plants and 6% shorter ‘Osaka White’ methanol) (A-Rest, SePro Corp., plants. A daminozide foliar spray of Carmel, Ind.), paclobutrazol, or Kale Growth 2500 mg·L–1, sprayed twice, resulted in 21% shorter plants for both chlormequat (2-chloroethyltrimethyl- Responses to cultivars. Spraying daminozide would ammonium ion) (Cycocel, Olympic provide optimal height control for the Horticultural Products, Mainland, Pa.) Daminozide, retail grower. Although spraying plus daminozide to ornamental kale daminozide twice controlled plant plants grown in 36-cell bedding plant Paclobutrazol, height and costs half the amount of trays. Ancymidol at 25 mg·L–1 and and Uniconazole an uniconazole spray at 16 mg·L–1, paclobutrazol at 15 mg·L–1 were effec- plant diameter was not affected with tive in producing a 20% smaller plant. daminozide, therefore a wholesale Tank mixes of chlormequat + grower who would desire a smaller 1 daminozide produced plants that were James L. Gibson and diameter plant should use a –1 uniconazole spray of 16 mg·L–1. 48% (1,000 + 800 mg·L ),56% (1,250 Brian E. Whipker2 + 1,250 mg·L–1), or 80% (1,500 + 5,000 mg·L–1) smaller when compared to the control, and a darker blue-green rnamental cabbage and foliage color was observed. ADDITIONAL INDEX WORDS. Brassica kale are attractive land- Lang (1998) in Texas, applied oleracea var. acephala, growth retar- scape plants for the fall and dant, B-Nine, Bonzi, Sumagic foliar sprays of daminozide between O –1 early winter garden. Commercial pro- 2,500 and 7,500 mg·L , paclobutrazol –1 SUMMARY. Ornamental cabbage and duction of ornamental cabbage and between 10 and 40 mg·L , and mul- kale (Brassica oleracea var. acephala) kale in the southeastern U.S. occurs tiple combinations of the two chemi- plants of cultivars Osaka White and during the late summer when warm cals to an ornamental kale cultivar in Nagoya Red were treated with temperatures promote extensive plant 8.9-cm (3.5-inch) pots. Daminozide paclobutrazol and uniconazole as growth. Growers face the challenge of (2,500 mg·L–1) plus paclobutrazol (20 foliar sprays or substrate drenches. maintaining a short, yet robust plant, mg·L–1) resulted in 41% shorter plants These treatments were compared to which looks proportional to pot size. when compared to the control. How- the industry standard of daminozide Plant growth regulators (PGRs) ever, plants treated with paclobutrazol foliar sprays. Applying drenches of –1 paclobutrazol (a.i.) at 4 mg/pot or are commonly applied to container- at 40 mg·L were comparable to the uniconazole (a.i.) at 1 mg/pot grown plants to inhibit stem elongation tank mix with a 34% shorter height. (28,350 mg = 1.0 oz) resulted in 6% and produce a more compact plant Whipker et al. (1994) found foliar or 17%, respectively, shorter ‘Osaka (Tayama et al., 1992). Commercial PGR applications of uniconazole ((E)-1-(p- White’ plants while a 2 mg/pot recommendations suggest using chlorphenyl)-4,4-dimethyl-2-(1,2,4- paclobutrazol drench or a uniconazole daminozide (2,2-dimethylhydrazide) triazol-1-yl-1-penten-3-ol)) (Sumagic, drench at 0.25 mg/pot resulted in (B-Nine, Uniroyal Chemical, Valent, USA, Marysville, Ohio) at 5 25% shorter ‘Nagoya Red’ plants. Middlebury, Conn.) at 1,500 to 3,000 mg·L–1 or daminozide at 2,500 and Although effective, the expense of mg·L–1 to achieve desired height control 5,000 mg·L–1 resulted in the shortest substrate drenches for both plant (Luczai, 1992; McAvoy, 1994). A few growth regulators (PGRs) would not plant height of two ornamental kale be economically feasible for growers PGR studies have been conducted on cultivars. This study was conducted in to use. Paclobutrazol foliar sprays at ornamental cabbage and kale, but all the the midwestern U.S. and used only a concentrations of up to 80 mg·L–1 previous work was conducted in geo- limited number of concentrations. (ppm) were ineffective in controlling graphical locations with milder produc- Barcel (1998), Kuehny et al. plant height and diameter of either tion temperatures, or during seasons (1998), and Lang (1998) evaluated other than the typical fall production several PGRs available to growers to- time of the southeastern U.S. day. They did not determine optimal Department of Horticultural Science, Box 7609, North During the winter and spring pro- Carolina State Univ., Raleigh, NC 27695-7609. concentrations of paclobutrazol or duction in California, paclobutrazol ((+)- uniconazole when applied as foliar This research was funded in part by the North Carolina β α Agricultural Research Service (NCARS), Raleigh, NC (R*,R*)- ([4-chlorophenyl] methyl- - sprays or drenches for plants grown in 27695-7643. Use of trade names in this publication (1,1-dimethylethyl)-1H-1,2,4-triazole- a container larger than 15.2 cm (6 does not imply endorsement by the NCARS of prod- 1-ethanol)(Bonzi, Uniroyal Chemical, ucts named nor criticism of similar ones not men- inches). Kuehny et al. (1998) and tioned. Thanks to Ingram McCall for her technical Middlebury, Conn.) drenches (a.i.) of Lang’s (1998) PGR research focused support, Wagner Greenhouses, Minneapolis, Minn. 1.25 to 2.5 mg/pot effectively inhib- on foliar concentrations for small con- for the seedling plugs, Fafard for the root substrate, Scotts for the fertilizer, and for grant support the Fred ited excessive height of ornamental kale tainers used in bedding plant produc- C. Gloeckner Foundation, Uniroyal Chemical Co., grown in 15.2-cm (6-inch) pots (Barcel, tion, and only ornamental kale was and the North Carolina Commercial Flower Growers’ 1998). Foliar sprays of paclobutrazol at evaluated. Recommended concentra- Assn. The cost of publishing this paper was defrayed in –1 part by the payment of page charges. Under postal concentrations up to 200 mg·L were tions of PGRs used in these studies regulations, this paper therefore must be hereby marked ineffective in inhibiting ornamental kale resulted in 20% to 35% shorter plants, advertisement solely to indicate this fact. growth, but the foliage became darker when compared to untreated plants, 1Research assistant. green and the center color intensified and these percentages are common 2Assistant professor. (Barcel, 1998). goals in plant growth regulator re- search (J. Latimer, personal commu- height, plant diameter, and center color plant height, when compared to the nication). Significant differences in diameter were tested by analysis of vari- untreated control (Table 1). Plants plant vigor between ornamental cab- ance by general linear model (SAS Inst., were 12% shorter when treated with bage and kale cultivars have been re- Cary, N.C.). Means for the cultivars and 2,500 mg·L–1 daminozide as a single ported (Whipker et al., 1998). Past treatment were separated by least sig- application, and when sprayed twice, research directed the authors to inves- nificant differences (LSD) at P ≤ 0.05. were 21% shorter, when compared to tigate the effectiveness of PGRs as Plant height and diameter values the untreated plants. Applying foliar sprays and substrate drenches for were regressed using the PROC REG daminozide at 2,500 mg·L–1 twice gave both ornamental cabbage and kale procedure (SAS Inst.) to determine the better control of height (21% smaller grown in the larger 20.8-cm (8-inch) best fit linear or quadratic model for plants) than the single application at pot commonly used by the industry. each PGR (paclobutrazol or 5,000 mg·L–1 (12% smaller plants). uniconazole) and application method PLANT DIAMETER. Plant diameter Materials and methods (foliar spray or substrate drench). Vari- was not controlled by daminozide for Ornamental cabbage and kale ables in the model were plant growth either cultivar and averaged 40.3 cm plugs (2.1 × 2.5 cm [0.8 × 0.95 inch] regulator concentration (Con) and in- (15.9 inches) (data not shown). Com- cells) of cultivars Osaka White and dicator variables for cultivar (Cult) mercial recommendations for Nagoya Red were transplanted into (‘Nagoya Red’ or ‘Osaka White’), with daminozide at 1,500 to 3,000 mg·L–1 2.96-L (0.78-gal) (20.8-cm-diameter β the full model being concentrationi = 0 (Luczai, 1992; McAvoy, 1994) may [8-inch]) round plastic containers on β β β × + 1Cult2 + 2Con + 3Con Cult2 + be appropriate for more northern cli- 20 Aug. 1998. The root substrate was β 2 β 2 × 4Con + 5Con Cult2, where mates. Southeastern U.S. growers may Fafard 4-P (Fafard, Anderson, S.C.), concentrationi = PGR concentration, i need to monitor the height of the which contained (v/v): 4 sphagnum = variable being regressed (plant height ornamental cabbage and kale crop on peat : 2 pine bark : 2 vermiculite: 1 or plant diameter), Cult2 = 1 if cultivar a regular basis when applying perlite. Plants were fertilized at each = ‘Osaka White’, 0 if otherwise (for daminozide. Although daminozide watering with 200 mg·L–1 N mixed β ‘Nagoya Red’), and k = estimated coef- may have no effect on plant diameter, . from Ca(NO3)2 4 H2O (15.5N–0P–0K) ficients (k = 0 to 5). it may be a tool for growth control by and KNO3 (13N–0P–36.5K) (Scotts, Terms of the model were judged retail and wholesale growers because Marysville, Ohio). Once every 2 weeks, to be significant or nonsignificant and of its economic advantage of costing a supplemental application of magne- included in the final model based on a $0.01 to $0.02 per pot, based on a . – α sium sulfate (MgSO4 7 H2O) at 96 mg·L comparison of F values at = 0.05. daminozide cost of $154/kg ($70/ 1 Mg and Peters 20–10–20 (Scotts, The NLIN procedure in SAS (SAS lb). Internode elongation and unde- Marysville, Ohio) (20N–4.4P–16.6K) Institute, 1982), as modified by Cox sirable expansive plant diameters may at 200 mg·L–1 N were applied. The (1992), was used to calculate linear- be avoided with higher concentrations plants were grown under natural plateau functions (model IV) relating than used in this study or multiple daylength. Thirteen PGR foliar sprays plant height and diameter to applications of daminozide. were applied 22 d after potting (using a paclobutrazol and uniconazole sub- volume of 204 mL·m–2 [0.5 gal/100 strate drench concentrations. The qua- Paclobutrazol drenches ft2]): paclobutrazol at 5, 10, 20, 40, or dratic and the linear-plateau models PLANT HEIGHT. ‘Osaka White’ plant 80 mg·L–1; uniconazole at 2, 4, 8, 16 or were compared to determine the best height responded linearly to increas- 32 mg·L–1; daminozide at 2500, 2500 fit based on r2 values. ing paclobutrazol substrate drench (twice, with the second application oc- concentrations (Fig. 1A). The response curring 14 d after the first), or 5000 Results and discussion of ‘Nagoya Red’ plants was best de- mg·L–1; and an untreated control. Ten Daminozide sprays scribed by a linear-plateau model with PGR drench treatments were also ap- PLANT HEIGHT. Plant height of both the smallest plants being 12.7 cm (5 plied 22 d after potting (using a volume cultivars responded similarly to inches) tall at concentrations of 2.7 of 300 mL [10 fl oz]) of solution per daminozide, therefore the data for both mg (the joinpoint) or greater (Fig. pot: paclobutrazol (a.i.) at 1, 2, 4, 8, or cultivars were pooled. Daminozide 1A). No further increases in control 16 mg/pot; uniconazole (a.i.) at 0.125, treatments of 2,500 or 2,500 mg·L–1 occurred at concentrations of 2.7 mg 0.25, 0.5, 1, or 2 mg/pot; or the un- sprayed twice significantly affected or greater, the plateau portion of the treated control. The experiment was a randomized complete-block design with Table 1. Effect of daminozide on growth of ornamental cabbage and kale. five single-plant replications of the 24 treatments. On 1 Nov., total plant height Mean plant ht Treatment (cm)z (measured from the pot rim to the top of the foliage), plant diameter, and the Untreated control 20.1 diameter of the center color (all diam- 2,500 mg·L–1 daminozide 17.6 eters measured at the widest dimension 2,500 mg·L–1 daminozide (twice)y 15.8 and turned 90°, and averaged) were 5,000 mg·L–1 daminozide 17.7 recorded. The suitability of plants for Significance *** the retail or wholesale markets was de- LSD (α ≤ 0.05) 1.6 termined by grower evaluations of the z2.54 cm = 1.0 inch. PGR treatments. yThe second daminozide foliar spray applied 14 d after the first. DATA ANALYSIS. Data for plant ***Significant at P ≤ 0.001. Daminozide was significant only by treatment, n = 10. at 2 mg. Optimal concentrations of paclobutrazol substrate drenches would be 4 mg for vigorous cultivars like ‘Osaka White’ or 1 to 2 mg for less vigorous cultivars like ‘Nagoya Red’. Although paclobutrazol drenches ef- fectively inhibited plant growth, the time involved in drenching a crop and the economic impact needs to be con- sidered. Paclobutrazol substrate drenches of 2 mg would cost the grower $0.06 per pot, while a 4 mg drench would cost $0.12, based on the cost of $116/L ($110/qt). Uniconazole drenches PLANT HEIGHT. The effects of uniconazole drenches were best de- scribed by a linear-plateau model (Fig. 1B). Uniconazole substrate drenches resulted in a significantly shorter plant height of ‘Nagoya Red’, with no fur- ther control above 0.7 mg. At this concentration, ‘Nagoya Red’ plants were 35% shorter, compared to the untreated control. ‘Nagoya Red’ plants had a stunted appearance, but when treated with 0.5 mg, the plants were 26% shorter than the untreated plants and in proportion to pot size. Concen- trations of 1 mg or greater were similar in inhibiting plant height of ‘Osaka Fig. 1. Plant growth regulator effects on plant height of ‘Osaka White’ (OW) White’ with plants being 17% shorter and ‘Nagoya Red’ (NR) ornamental cabbage and kale. Regression lines were than the untreated plants. generated from the best-fit model, and points are means for each treatment (n PLANT DIAMETER. The effects of NS,**,*** ≤ = 5). Nonsignificant or significant at P 0.01, 0.001, respectively; L = uniconazole substrate drenches on linear, Q = quadratic, and LP = linear-plateau, X = joinpoint; (A) 0 plant diameter were best described by paclobutrazol substrate drench for OW: L***, NR: L***Q***LP***; (B) uniconazole substrate drench adjusted for OW: Q**LP***, NR: Q***LP***; (C) a linear-plateau model (Fig. 2B). No paclobutrazol foliar spray for OW: L**, NR: LNS; (D) uniconazole foliar spray further control of diameter was ob- for OW: L***, NR: L***. Substrate drench rates are expressed as mg of active served for ‘Osaka White’ at concentra- ingredient. 2.54 cm = 1.0 inch. tions above 0.7 mg or with 0.5 mg for ‘Nagoya Red’. Plant diameter was 20% smaller for ‘Osaka White’ at 0.7 mg line. ‘Osaka White’ plants were 6% fit on shipping carts and trucks. and 29% smaller for ‘Nagoya Red’ at shorter when treated with 4 mg and CENTER COLOR DIAMETER. Center 0.5 mg, when compared to the un- 11% shorter when treated with 8 mg of color diameter was 49% smaller for treated control plants. paclobutrazol, and the ‘Nagoya Red’ ‘Nagoya Red’ plants treated with Marketable wholesale shipping kale plants were 34% shorter when paclobutrazol drenches of 8 mg (data plants of ‘Osaka White’ were produced treated with 2.7 mg, when compared not shown, P ≤ 0.05). No other PGR with drench concentrations of 0.7 to 1 to the untreated control plants. treatment had an effect on center color mg, while 0.5 mg produced market- PLANT DIAMETER. Both ‘Osaka diameter. able ‘Nagoya Red’ plants. Economi- White’ and ‘Nagoya Red’ plant diam- Although greater height control cally, a 0.5 to 1 mg drench of eters were best described by linear- was observed at 8 mg for ‘Osaka White’ uniconazole would cost $0.12 to plateau models with no additional re- with plants being 11% shorter, when $0.23, respectively, per pot. These sponse in plant diameter being ob- compared to the untreated control, expenses are based on the cost of $116/ served at concentrations of 4.3 mg or the plant diameter was detrimentally L for uniconazole. greater (Fig. 2A). ‘Osaka White’ and affected (60% smaller). Paclobutrazol ‘Nagoya Red’ plants were 33% and drenches of 4 mg or greater were ex- Paclobutrazol sprays 30% smaller in diameter, respectively, cessive and resulted in a stunted ap- PLANT HEIGHT. Paclobutrazol fo- for these concentrations. Smaller di- pearance for ‘Nagoya Red’. Plant di- liar sprays at concentrations of up to ameter plants would be an advanta- ameter was 31% smaller when treated 80 mg·L–1 were ineffective in inhibit- geous trait to wholesale growers be- with 4 mg for ‘Osaka White’ and 14% ing plant height of ‘Nagoya Red’ (Fig. cause a greater number of pots could smaller for ‘Nagoya Red’ when treated 1C). ‘Osaka White’ exhibited a posi- and ‘Nagoya Red’ (Fig. 1D). An 8 mg·L–1 application of uniconazole re- sulted in a 3% shorter plant height for ‘Osaka White’ and 7% for ‘Nagoya Red’. This concentration for both cul- tivars may be appropriate for retail growers who do not need to control height for shipping purposes. A con- centration of 16 mg·L–1 significantly decreased plant height by 6% and 15%, when compared to the untreated con- trol for ‘Osaka White’ and ‘Nagoya Red’, respectively. Wholesale growers may desire concentrations as high as 32 mg·L–1 to control height of vigor- ous ornamental cabbage cultivars like ‘Osaka White’. PLANT DIAMETER. There was a lin- ear relationship between increasing concentrations of uniconazole foliar sprays and plant diameter for both ‘Osaka White’ and ‘Nagoya Red’ (Fig. 2D). The plant diameters for ‘Osaka White’ and ‘Nagoya Red’ were 11% and 17% smaller, respectively, than the untreated control plants when sprayed with 16 mg·L–1 uniconazole. An optimal concentration of uniconazole to produce marketable plants in retail settings would be 8 mg·L–1 for ‘Nagoya Red’. A concen- tration of 16 mg·L–1 limited stem elon- Fig. 2. Plant growth regulator effects on plant diameter of ‘Osaka White’ (OW) gation and lateral expansion of both and ‘Nagoya Red’ (NR) ornamental cabbage and kale. Regression lines were cultivars. Although uniconazole at 16 generated from the best-fit model, and points are means for each treatment (n mg·L–1 did not result in plants be- NS,**,*** ≤ = 5). Nonsignificant or significant at P 0.01, 0.001, respectively; L = tween the threshold of being 20 to linear, Q = quadratic, and LP = linear-plateau, X0 = joinpoint; (A) paclobutrazol substrate drench for OW and NR: L***Q***LP***; (B) uniconazole 30% shorter for ‘Osaka White’, the substrate drench for OW: Q**LP***, NR: Q***LP***; (C) paclobutrazol foliar treatment did result in significantly sprays were not significant; (D) uniconazole foliar spray for OW: L***Q**, NR: smaller plant diameters. Our recom- L**. Substrate drench rates are expressed as mg of active ingredient. 2.54 cm = mended concentrations of 8 to 16 1.0 inch. mg·L–1 for southeastern U.S. growers is slightly higher than the concentra- tive response of greater plant height as PLANT DIAMETER. Paclobutrazol tion of 5 mg·L–1 recommended for the paclobutrazol foliar spray concen- foliar sprays at concentrations of up to northern U.S. growers (Whipker et al., tration increased. The ineffectiveness of 80 mg·L–1 were also ineffective in con- 1994). Based on the cost of $116/L, paclobutrazol foliar sprays in control- trolling plant diameter of either ‘Osaka the 16 mg·L–1 uniconazole spray would ling height was in agreement with Barcel White’ or ‘Nagoya Red’ (Fig. 2C). cost $0.04 per 2.96-L pot, which was (1998) who found 200 mg·L–1 was only Paclobutrazol applied as a foliar 3 times less expensive than the slightly effective on ornamental kale. spray does not appear to be useful to uniconazole drench at 0.5 mg or the These findings are in contrast to those of wholesale growers in the southeastern paclobutrazol drench at 4 mg. Kuehny et al. (1998) and Lang (1998) U.S. for controlling growth of orna- where paclobutrazol foliar sprays of 10 mental cabbage and kale grown in Conclusion to 40 mg·L–1 inhibited plant growth of larger 20.8-cm containers. Similar re- Although substrate drenches of ornamental kale. Greater control of plant sults were reported by Barcel (1998) paclobutrazol at 2 to 4 mg and height with paclobutrazol foliar sprays with foliage color being darker on uniconazole at 0.5 to 1 mg produced of 10 to 40 mg·L–1 by Kuehny et al. plants treated at concentrations of 20 compact plants for the retail and whole- (1998) and Lang (1998) may be a direct mg·L–1 or greater. sale grower, the economic aspect in result of restricting growth through the growing ornamental cabbage and kale use of smaller containers or due to Uniconazole sprays needs to be considered. Method of regional climate differences. This high- PLANT HEIGHT. There was a linear application is an important consider- lights the need to conduct PGR trials in relationship between increasing con- ation in determining the most cost- multiple locations to account for differ- centrations of uniconazole foliar sprays effective way of inhibiting plant growth. ences in climate and timing of the crop. and plant height for both ‘Osaka White’ Daminozide sprayed at 2,500 mg·L–1 was effective in limiting stem elonga- tion of ornamental kale cultivars, and cost $0.004 per pot as a single applica- tion or $0.01 when sprayed twice. Two applications of 2,500 mg·L–1 daminozide may be applicable to wholesale southeastern U.S. growers who desire an economical ($0.01) and effective measure for inhibiting height of ornamental cabbage and kale. A uniconazole foliar spray of 16 mg·L–1 was effective in inhibiting plant growth, but would cost the grower $0.04 per pot. Although more expensive, a uniconazole foliar spray of 16 mg·L–1 resulted in both a smaller plant height and smaller plant diameter, when com- pared to daminozide applied twice at 2,500 mg·L–1.

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