Using sumagic on bedding plants

Editor’s note: This article is from the archives of the MSU Crop Advisory Team Alerts. Check the label of any pesticide referenced to ensure your use is included.

Sumagic (uniconazole, Valent USA Corp.) is a plant growth regulating chemical that inhibits stem elongation and is used to control height of greenhouse crops. Sumagic is one of the more active chemicals available for controlling plant height. We performed experiments at MSU to determine suggested rates for use on greenhouse crops grown in Michigan during the finish stage.

We applied different rates of Sumagic as a single foliar spray (2 quarts per 100 ft2) to celosia ‘Apricot Brandy,’ marigold ‘Inca II Orange,’ petunia ‘Prostrate Wave Rose,’ and salvia ‘Vista Red’ grown in 4-inch pots. Applications were made eight days after transplant from a 288-cell plug. The rates of Sumagic used ranged from 1 to 20 ppm. In addition, we also used Bonzi as a spray at 8 ppm for comparison. Plants were grown in the late spring under a 16-hour day in a glass greenhouse set at 68°F.

We found that Sumagic can be used on these bedding plants as a spray at low rates soon after transplant to achieve a moderate reduction in height with little or no delay in flowering. Based on our results, the accompanying table provides suggested rates of Sumagic when used as a single foliar spray soon after transplant into the finish container.

Bedding plant

Suggested rate of Sumagic as a single foliar spray

Celosia 'Apricot Brandy'

1/2 to 1 ppm

Marigold 'Inca II Orange'

5 to 10 ppm

Petunia 'Wave Rose'

2 1/2 to 5 ppm

Salvia 'Vista Red'

1 to 2 1/2 ppm

If a stronger height reduction is desired, or for more aggressive plants, we suggest making a second application as needed. For less aggressive plants, lower rates (¼ to ½ ppm) of Sumagic may be more appropriate. Sumagic begins controlling stem elongation soon after application, so the magnitude of response is evident within one week, and the need for more applications can then be determined. The effects of Sumagic on stem elongation may persist for three to five weeks or even longer, depending on the rate, the plant treated and its growing conditions.

Sumagic is absorbed primarily by stems, so good stem coverage is critical for effective control of elongation. Uniform spray volume is important because roots readily absorb Sumagic, and excess solution that drips into the media can be taken up by the plants. We recommend that you conduct your own trials on a small scale first to determine appropriate rates for your conditions.

For a more complete report and to see photos of treatment results from this experiment, please see this article, which originally appeared in the April 2005, issue of GPN magazine.

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