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Have your PGR plans ready before the spring push
By Dave Barcel, Senior Technical Manager, OHP, Inc.

Many of you have spring crop seeds planted and/or will soon pot-up vegetative cuttings to begin rooting. In a quick 6-to-8 weeks the crop is finished and out the door to sales. From start to finish sounds like a long time (12 weeks maybe more) but in reality it goes fast. Now is the time to review your production notes from last year. Many of our spring crops benefit from one or more PGR applications, which can be used to control growth, tone up the crop or simply hold a crop over if poor sales weather exists. There are several methods to consider when using PGRS.

Early media spray applications and plug and liner dips can provide early control of hypocotyl stretch of problematic plants like cosmos, marigold, snapdragon, salvia etc. Typically, growers use low rates of paclobutrazol (Paczol®) for dips – e.g. for salvia sp. use 1/2 to 1 PPM soak for 15 seconds. Another technique is to apply PGR sprays or drenches about a week after transplant into the finish pot. As an example for petunia, a general spray of Paczol sprayed at 15-30 PPM will finish the plant height nicely given a 6-to-8 week finish program.

Similarly, a Paczol drench at 2-4 PPM should work equally well. A handy tip for Paczol use is: Paczol sprayed at 10PPM is equal to about 1 PPM drenched. For those of you not familiar with the use of the very active PGRs like Paczol, you may want to try B-Nine® or Cycocel® or even a tank mix of the two, which provides a greater PGR response. Using the petunia example, B-Nine at 2500- 5000 PPM, or Cycocel at 800-1250 PPM should provide good growth control to finish. The combination of B-Nine and Cycocel at 2500 and 1250 PPM, respectively,would be 20-to-30 percent more active than the two applied separately.

Evaluate your PGR applications about two weeks after application.You should see darker green color forming, slower growth, etc. If activity is less than desired, then re-apply your PGR treatment at the initial rate. Toning up the crop can be done with a 1/2 rate application two-to-three weeks from sale. This lower rate also helps hold size if weather is not conducive to sales. These rate recommendations are general in nature; those in the north may use lower rates and those in the south will use higher rates.

Paczol and B-Nine are registered trademarks of Chemtura Corp.Cycocel is a registered trademark of BASF Corp.