B-Nine + Cycocel: The advantages for poinsettias and pansies By Kelly P. Lewis, Jim Faust and James D. Sparkman IV

Research on B-Nine/Cycocel tank mixes at Clemson University helps determine optimal combinations of these PGRs for use on poinsettias and pansies.

B-Nine and Cycocel have been effectively used as a tank mixgrowth regulator application for many years. The major benefit of this tank mixis that it provides an easy-to-apply, medium-activity growth regulatorapplication. The spray volume is not crucial, so any grower can effectively andsafely use it. The B-Nine and Cycocel tank mix (B-Nine/CCC) is particularlyuseful in situations where B-Nine and Cycocel are individually insufficient tocontrol plant height. Thus, B-Nine/CCC fits a niche between the lower-activityproducts (B-Nine and Cycocel) and the higher-activity products (Bonzi andSumagic).

Growers have different methods of determining the bestB-Nine/CCC combination to use. A common technique is to identify the rate ofCycocel that provides a reasonable measure of control without causing anyphytotoxicity, then to adjust the rate of B-Nine to provide the desiredstrength of growth regulator effect. Our approach was to apply a range ofB-Nine (0-4,500 ppm) and Cycocel rates (0-1,500) to identify the interactiveeffects of these two products when applied as a tank mix. We applied 14combinations of B-Nine/CCC (see Table 1, page 60) to poinsettias and pansieswith the goal of identifying the optimal tank mix combination.


Rooted cuttings of ‘Freedom Red’, ‘SuccessRed’ and ‘Winter Rose Dark Red’ were potted on July 26 andgrown as straight-ups (unpinched). Short days were started on August 14, andgrowth regulators were also applied during the first short day. Growthmeasurements were recorded at first pollen.

B-Nine/CCC affected final plant height and total bract areasimilarly for all three poinsettias grown in this study (see Figure 1, page58). The highest rate of B-Nine/CCC (4,500:1,500 ppm) decreased the heights ofthe three cultivars Á between 16 and 21 percent compared to the control(0:0 ppm; see comparison photos, page 56). B-Nine and Cycocel each had a lineareffect on height reduction, i.e., each additional amount of B-Nine or Cycocelapplied resulted in an additional reduction in height. B-Nine had a greaterimpact than Cycocel on overall height; however, a wider range of B-Nine rates(0-4,500 ppm) were applied compared to Cycocel (0-1,500 ppm).

The total bract area (the total area of the six largestbracts) of Freedom and Success, and the flower head diameter of Winter Rosedecreased by 42, 28 and 19 percent, respectively, when comparing the highestrate of B-Nine/CCC (4,500:1,500 ppm) to the control (0:0 ppm; see Figure 1,above). Individually, B-Nine and Cycocel resulted in a linear decrease in bractarea. B-Nine/CCC did not decrease the internode length between the transitionalbracts, so the flower head was not more vertically compact.

We don’t see many growers using B-Nine alone onpoinsettias, but our data suggest this would be a very effective product to useduring the vegetative stage of poinsettia Á

production, e.g. on stock plants, in propagation or shortlyafter transplant and before short days. Considerable data suggests that B-Ninewill delay flowering of poinsettias. For this reason, we applied B-Nine in thisstudy during the first short day, i.e., the first day of flower initiation, anddid not observe any effect on time to flower. Growers in cooler climates andlower-light conditions will observe potentially greater negative effects ofB-Nine on poinsettia flowering. So, caution is urged. B-Nine should never beapplied after the start of short days, and in Northern climates September 1might be a safe cut-off date for natural-daylength poinsettia crops. Please conductyour own trials before risking an entire crop on a new growth regulatorapplication. 


Plugs of ‘Delta Pure Yellow’, ‘MajesticGiants Purple’ and ‘Colossus Yellow Blotch’ pansies werepotted on August 16. The same 14 B-Nine/CCC treatments were used on the pansiesas were used on the poinsettias. The treatments were applied on August 29 andrepeated on September 5 and September 13. Data were collected when two flowershad fully opened.

With the highest application rate of B-Nine/CCC (4500:1500ppm), height or shoot length of Colossus Yellow Blotch and Delta Pure Yellowdecreased by 29-37 percent compared to the control, but height of MajesticGiants Purple decreased by only 8 percent (see Figure 2, above).

We measured several different morphological characteristics,but found that the potential benefit of B-Nine/CCC was most accuratelyrepresented by the tilt. “Tilt” is our term describing the degreeto which the primary shoot tip slanted away from the center of the pot (seeFigure 3, page 61). Tilt describes the floppiness of the pansy in the pot. Tiltdecreased in Colossus Yellow Blotch, Delta Pure Yellow and Majestic GiantsPurple by 49, 59 and 27 percent with the highest tank mix rate (4,500:1,500ppm) compared to the control (see Figure 2, above).

We also observed that petiole length was slightly reduced bythe growth regulator applications; however, each variety appeared to responddifferently to B-Nine and Cycocel. For example, B-Nine reduced petiole lengthof Colossus Yellow Blotch and Majestic Giants Purple while Cycocel reducedpetiole length of Delta Pure Yellow.

Searching for the perfect combination

Our data suggest that there isn’t a perfectcombination of B-Nine and Cycocel to apply to poinsettias or pansies. Manydifferent combinations will provide very similar results. For example, in ourstudy the 1,000:1,000, 1,500:500 and 2,000:0 B-Nine/CCC treatments producedvery similar results. Thus, we don’t believe there is a perfectcombination. Any combination that provides a total plant growth regulatorconcentration of 2,000-3,000 ppm B-Nine and Cycocel will provide similarresults on the poinsettia varieties used in this study. However, lower ratesare required to control the height of less-vigorous varieties. The bottom lineis that the exact ratio of the two products is not critical. Growers mustidentify the overall strength of application that is required and choose acombination that will provide the desired effect. As a starting point we oftenuse a 3:1 B-Nine/CCC ratio. For example, 1,500:500 ppm provides a low rate,3,000:1,000 ppm provides a medium rate and 4,500:1,500 provides a high rate forpoinsettias. The overall effectiveness depends on plant vigor and the currentgrowing conditions (temperature and light).

Pansies showed more variability between varieties inresponse to B-Nine/CCC, although the reduction in tilt was similar for thethree varieties tested. Relatively high rates of B-Nine/CCC and multipleapplications were required to produce beneficial results on pansies.


Cycocel is typically effective at rates greater than 1,500ppm; however, the potential for phytotoxicity keeps most growers fromexperimenting with higher rates. The typical Cycocel damage produces”bleached-out,” yellowed spots on the leaves or along the leafmargins. Interestingly, we observed Cycocel damage on only one treatment in ourstudy: 0 B-Nine, 1,500 Cycocel on Winter Rose poinsettia. We did not observeany damage to Winter Rose when the same concentration of Cycocel (1,500 ppm)was applied in combination with any rate of B-Nine. We have also heard growersreport less phytotoxicity when B-Nine is combined with Cycocel versus Cycocelbeing applied alone. This suggests that rates greater than 1,500 ppm Cycocelshould be examined in the future when Cycocel is tank-mixed with B-Nine.


The term “synergism” has been used to describethe interactive effectiveness of B-Nine and Cycocel. Synergism implies that theactivity of the two individual products is enhanced when combined. Our datasuggests that B-Nine and Cycocel have an additive effect. In other words, theindividual responses to B-Nine and Cycocel are added together when the productsare combined. There does not appear to be any enhancing effect as a result ofthe tank-mix combination.

Future Work

At Clemson University, we are currently in the process ofscreening an array of bedding plants for their responses to B-Nine/CCC. Thisinformation will published in a future issue of GPN.

Kelly P. Lewis, Jim Faust and James D. Sparkman IV

Kelly Lewis is a research specialist, Jim Faust is an assistant professor and Jay Sparkman is an undergraduate student in the Horticulture Department at Clemson University, Clemson, S.C. They may be reached by phone at (864) 656-4966 or E-mail at jfaust@clemson.edu.

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