Bonzi: Just a Little Off the Top

Chris Fifo

Why is getting a haircut such an issue for some kids? My boys are complete opposites when it comes to haircuts. One loves it, but the other hates getting his hair cut and wants to have it long.

Maybe it’s because I tortured him with a summertime buzz when he was younger. Or maybe he’s seen pictures of his Dad in his younger days. If we could just get the perfect cut and then keep it from growing …

The same goes for our hanging baskets. We would have fewer issues if we could just get them to the perfect size and hold them there.

Flowering annual baskets have always been very labor intensive for us. We rely on giving haircuts to many varieties. In some cases it’s just a little off the top for styling; in other cases, it resembles the summertime buzz. By trimming we get a more compact, well-branched basket with more flowers.

But things are different this year. We’re trying to eliminate as much trimming of our baskets as possible. Obviously, it’ll be a huge labor savings. But more importantly, it’ll reduce the potential spread of virus.

As many of us are aware, there have been reports of Tobacco Mosaic Virus (TMV) in certain vegetative petunia varieties. Despite the supplier’s best efforts and strict protocols, some infected crops have made it into our greenhouses and it’s now up to us to contain the spread.

With the ease that this virus can spread and a host range that includes some of our most popular basket varieties, the best thing we can do—after discarding all symptomatic plants and sanitizing the area—is to minimize our handling. When plants must be handled, it’s been recommended to spray plants with a 10% to 20% non-fat dry milk solution with a spreader/sticker to inactivate the virus on the leaf surfaces.

To increase branching and eliminate premature flowers in the plug stage, we use Florel about two weeks after rooting. One spray at 500 ppm works well, but many varieties still get pinched before planting.

To reduce the amount of trimming we do on our 11-in. baskets, we’ve been using Bonzi (paclobutrazol to be politically correct) as a drench. This has been the standard for PGR drenches for a long time, but I’ve had very little experience.

The majority of my experience was with Supertunia baskets years ago. If they were alive today, they probably wouldn’t have grown yet. So I’ve proceeded with caution by reading literature and, strangely enough for me, the label.

Here’s what I’ve learned:

Bonzi is volume dependent, especially in the soil, so proper calibration of my injector and accurate calculations for the number of baskets on each drip line is critical. Adding dye or iron chelate (red iron) to the Bonzi concentrate helps me determine when the solution has made it to the emitters so I can measure the output. Variable: The baskets closer to the front of the line get more volume than the end of the line.
Rate (ppm) varies greatly.
Lobularia has responded well to 1 ppm; 3 ppm is too much.
Some verbena varieties responded well to 1 ppm; others took a second application.
Calibrachoas are a monster! Three ppm isn’t enough. A second drench was applied three weeks later. Results pending. Next year, I may start with 5 ppm on the more vigorous varieties.
Timing is important. Less than two or three weeks after transplant can stunt growth. I waited three to four weeks until they were going strong before drenching. Early on a sunny day is best to get uptake of the PGR into the plant.
Combo baskets are a challenge, especially if you include a calibrachoa. I waited a little longer and used an in-between rate for the included varieties.
Temperature is a factor. Our warm houses require a higher rate; whereas our perennial houses—with as much as a 20 degrees negative DIF—require much less.
Fascination PGR as a spray can overcome Bonzi overdoses.

With a little Bonzi our baskets have great color and we have overcome many of our “haircut” issues. I wonder if it works on teenagers …? GT

Chris Fifo is Technical Services Advisor for Swift Greenhouses, Inc. in Gilman, Iowa.