Branching out

Nursery growers have come a long way when it comes to the use of plant growth regulators. When container nurseries started shifting from growing mainly traditional woody plants to flowering crops, PGRs became more popular. Nurseries focusing on roses, hydrangeas, buddleias, sages and other blooming plants became well-versed in the application of PGRs.

There are several types of PGRs, and they all affect plants in different ways (see sidebar below).

Some nursery growers have been using growth retardants on perennials for years. They may need help with a new crop or cultivar, but for the most part, they have figured out what works for them and are comfortable with their method.

Joyce Latimer, extension specialist for greenhouse crops at Virginia Tech, says the PGRs that are generating the most interest among growers are branching compounds. PGRs that enhance branching include active ingredients like ethephon, benzyladenine, dikegulac sodium or methyl esters.

“After the season starts winding down, I’ll get e-mails from growers who want to do cultivar trials with Configure or with Augeo,” she says.

These growers are seeing new opportunities to use branching enhancers to improve crop quality. They want to know what kind of research has been done for specific PGRs and specific plants, and how to apply that research in their own nursery.
 

What works with branch enhancers

Latimer says many types of perennials would benefit from branching compounds, especially more upright plants that struggle to fill the pot.

Echinacea, for example, was one of the first crops to be labeled for Configure because of this particular issue. Another plant with specific problems is Phlox paniculata. Branch enhancers can be used with lobelia to quicken pot fill. Also, types of plants that are basal branchers like leucanthemum and heuchera can benefit from this type of PGR.

“Anything that is kind of weak to fill the pot,” Latimer says. “For a lot of the more upright plants, it helps them to get the branching. And we’re getting that branching very low in the plant, which is good.”

Plenty of upright plants can benefit from lower branching. Often, increasing the number of branches also improves the number of flowers.

“It looks fuller and aesthetically it’s more attractive than a bush at the top,” Latimer says.

There are some specific tactics with applying branching compounds that can increase your odds of success. For best results, plan for multiple applications. But leave at least two weeks between applications. Latimer encourages growers to perform their first application as early as possible. For liners, it needs to be done as soon as the liners are actively growing, then again two weeks later or shortly after transplanting.

“We are really seeing a huge improvement with multiple applications, particularly with Configure. With Augeo you have to stay in that lower 400-600 part per million range, because if you get into the higher range, 800 or 1,600, you get too much stunting with the second application. I’m convinced that two applications results in better branching. But with Augeo you have to look at growth control as well.”

There are a few cautions to be aware of when applying branching compounds. As with all PGRs, they should only be applied when the plants are not under any kind of stress.

“Any plant being treated by a chemical needs to be healthy and happy,” Latimer says.

For best results, growers should make applications under slow-drying conditions to increase the amount of time for uptake of the material.

“You want the leaves to stay wet as long as they can,” Latimer says. “We prefer early morning, and cloudy days if you get that option, because the highest relative humidity is usually early in the morning, which makes it a good time to make the application.”
 

New research

Some of the newest research into branching compounds involves incorporating ethephon dips and drenches into perennial production. Also, Amy Fulcher of the University of Tennessee’s Department of Plant Sciences recently published the results of her experiments treating Hydrangea paniculata with dikegulac sodium (Augeo), benzyladenine (Configure) and ethephon (Florel).

Latimer is interested in finding out more about how some crops respond to the combination of a PGR and a pinch.

“We’ve done some pinch comparisons, but I think it’s time we looked at some combinations and some of these crops could probably go through multiple pinches,” she says. “If we could eliminate a couple of those and just do one to shape up the plant, we may come out with the highest quality plant.”