PGRs: They’re Not Just for Annuals Anymore By Steve Engle

It's a well-known fact that herbaceous perennials are growing in popularity with today's consumers. The reasons are many, from the inherent convenience and value of perennials to the ever-expanding variety of perennials available to homeowners and landscape professionals.

"The popularity of herbaceous perennials has been increasing steadily over the past 20 years," notes Joyce Latimer, extension specialist for greenhouse crops at Virginia Tech University and a nationally recognized expert on perennial production. "Today's educated consumers appreciate the convenience and value of perennial plants. Plus, there's been a lot of breeding work done with perennials in recent years, leading to more and more beautiful colors and longer bloom periods."

Erik Runkle, associate professor of floriculture at Michigan State University, sees many of the same market forces working in northern climates. "While many homeowners are spending less time in their gardens, they still want beautiful landscaping. So there's a growing interest in the things perennials can offer, from a lower amortized cost and less maintenance to a wider range of sizes, shapes and colors."

"Perennials give consumers a lot more bang for their buck," says Jeff Lewis of Riverview Flower Farm in Riverview, Fla. "In this area, we've seen a big increase in the demand for tropical perennials like pentas, lantana, Persian shield and others. Most of our varieties over-winter well here in Florida, so they offer consumers several years of color from their initial investment."

Managing Growth a Must

By their very nature, most perennial species present a constant challenge to growers striving to ship compact, uniform plants. "In general, perennials are more vigorous than annuals," states Latimer. "While current breeding programs are working to develop more manageable varieties, plant growth regulators are a key to producing compact, marketable plants."

"There are so many aggressive perennial varieties, something needs to be done by growers to inhibit extension growth," adds Runkle, "In addition to controlling height and radius, compounds that stimulate branching are a definite need in perennial production."

Brad Hawcroft of Layman Wholesale Nurseries, Johnson, S.C., suggests another reason for incorporating PGRs into most perennial production programs. "Since most perennials are grown outdoors, you have more variability in temperature, light and moisture than you do with greenhouse annuals. And with perennials, you can't 'schedule' PGR applications like you can with greenhouse crops. You have to go more by what the plant needs, when it needs it."

Perennial Program Production Choices

When asked which PGRs should be part of any perennial grower's production program, Latimer and Runkle listed a handful of well-known brands.

"I see Configure (2 percent 6-BA) and Dazide 85 WSG (85 percent daminozide) playing key roles in perennial production," says Latimer. "Configure is an excellent branching agent for many perennial species, while Dazide helps growers produce stronger, more compact plants with the greener leaves retailers and consumers prefer."

In the Great Lakes region, Runkle sees uniconazole (Concise and Sumagic) as one of the more versatile PGR compounds on the market. "I'd say perennial growers in this area lean more toward uniconazole because of its wide range of uses. Of course, Configure and Augeo are becoming increasingly popular as branching agents."

While Configure and Augeo both serve as branching agents, each product has its own unique mode of action. Configure contains the active ingredient benzyladenine, a synthetic cytokinin that interrupts apical dominance and stimulates auxiliary buds to break. Meanwhile, the active ingredient in Augeo (dikegulac-sodium) works by disrupting cell wall integrity, resulting in a pinching effect on the plant.

From a grower's perspective, Marc Verdel of Battlefield Farms in Rapidan, Va., lists Augeo, Configure, Dazide and Florel as the cornerstone PGRs in his operation. "In addition to controlling height, these products help us grow a fuller, better-looking plant. It's all about meeting retailer and consumer expectations, and PGRs certainly help us do that."
In South Carolina, Brad Hawcroft counts on drench applications of Piccolo (paclobutrazol) and foliar applications of Concise to manage more than 200 acres of hostas, gallardia, dianthus and other perennials. "We use PGRs to keep plants smaller, so they ship better with more branches and a deeper, greener color."

Further south, Florida grower Jeff Lewis uses PGRs to meet the stringent quality control standards of large retail chains. "When it comes to the big box stores, size really does matter. So we mostly use Piccolo 10 XC and Concise as our main PGRs and then come in with Dazide for added synergy. By doing so, we're able to produce compact, well-toned plants with excellent shipping characteristics and a longer shelf life."

Conduct Your Own Trials

University researchers counsel growers to conduct their own trials to determine appropriate PGR application rates, timing and methods for their operations. "What's effective for growers in one area might not work as well in another," cautions Runkle. "Do your own on-site trials. Learn as much as you can about each PGR. Set some untreated plants aside as controls so you can have something to compare your treated plants to in terms of growth response."

"Certain species such as veronica and hibiscus are uniformly sensitive to certain PGRs, such as paclobutrazol," says Latimer. "So I always advise growers to test lower rates to start with and observe the response of different varieties to different PGRs. It's really the only way to fine-tune your PGR program for optimum results."

In summarizing the growing adoption of PGRs by perennial growers, Latimer states, "On average, nursery growers have less experience with plant growth regulators than greenhouse operations. But as more and more perennial growers get comfortable with PGRs, I think you'll see perennials with better shape, better shipability and better shelf life."

PGRs: They’re Not Just for Annuals Anymore

Steve Engle

Steve Engle is president and chief creative officer of Engle Creative Solutions LLC. He can be reached at [email protected] or 573.823.4723.

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