PGRs: They’re Not Just for Annuals Anymore

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,” noted Dr. 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.”

Dr. 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

“Perennials give consumers a lot more bang for their buck,” observed 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 perennials species present a constant challenge to
growers striving to ship compact, uniform plants. “In general, perennials are more
vigorous than annuals,” Dr. Latimer stated. “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,” added Dr. Runkle, “In addition to controlling
height and radius, compounds that stimulate branching are a definite need in perennial

Brad Hawcroft of Layman Wholesale Nurseries, Johnson, SC, suggested 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.”

Must-have PGR products

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

“I see Configure (2% 6-BA) and Dazide 85 WSG (85% daminozide) playing key roles
in perennial production,” said Dr. 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, Dr. 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

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,” cautioned Dr.
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,” said Dr. 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, Dr. Latimer
stated, “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.”