When Less is More

Joanne Lutz

How to use Bonzi micro-drenches on poinsettia.  
To avoid problems at retail with your poinsettia crop, it’s key to control plant height throughout the growing cycle. Research has shown that most plant stretch occurs in the first three hours of the day, beginning at first light.
One method that greatly reduces stretch is to drop the temperature during this time frame, by 5F below the night temperature. Discontinue this technique when the cyathia become
When it comes to maximizing bract expansion, poinsettias benefit from as little PGRs as possible—the less applied, the better. Foliar sprays of PGRs are more likely to reduce bract size than drenching. Bonzi drenches can be utilized to encourage uniform poinsettias of ideal height without significant reductions in bract size.
Bonzi “micro-drenches” were developed and named by Dr. Jim Barrett from the University of Florida. This technique utilizes drenches of low rates of Bonzi, usually in the range of 1/10 to 1/8 ppm, which can be made as often as weekly if required throughout the production cycle. (After October 25, higher rates can be used as needed with a reduced impact on bract size. Read on for details.)
Graphical tracking is very helpful in managing plant height among varieties of varying vigor. Such tracking ensures that data-based decision making is employed. Graphical tracking is available at

Starting after October 25, higher drench rates (0.25 to 1.0 ppm) may be used to provide stronger hold if needed with only a slight reduction in bract size. Very vigorous varieties, for example, would apply a Bonzi drench at a rate of 1.0 ppm. Consult with your supplier for varietal response information to determine if a Bonzi drench rate would be beneficial or necessary to avoid late-season stretch in your crop. GT

Joanne Lutz is a GGSPro Technical Support Representative for Griffin. She can be reached at