Landscapers use plant growth regulators to solve unique problems

The trick in controlling grass and ornamental bushes is to let them know who’s boss. Willy-nilly, grow-as-they-please plants do not fit profitably into a 21st-century landscape business plan. One tool to keep plants in line through a growing season is application of plant growth regulators, or PGRs.

Growth regulators have been around for half a century. Even so, their use by U.S. landscape maintenance companies is hardly universal today. Utilization varies widely between commercial and residential projects, southern and northern regions of the country – even between different generations of professionals.

“My goal is to get people out there to understand how PGRs work,” says Clint Formby, technical specialist with SePro turf and landscape products. “Young guys are working with plant growth regulators more and are starting to understand the labor savings from doing so. It’s a fairly new concept.”

The idea of slowing the growth of grasses and plants has been explored by horticulturalists since the 1940s with roadside vegetation versions coming on the market in the 1950s. In subsequent decades, the applications were refined so that now they can be used in sophisticated ways on a variety of grasses, plants (including trees) and media. Early regulators were anything but sophisticated.

“The first generation of plant growth regulators in the late 1950s was essentially a herbicide used in low concentrations,” says Bruce Branham, crop science professor at the University of Illinois. “They were more growth inhibitors that actually stopped growth. The things we use today truly regulate growth. They produce the same or better quality grasses or plants as untreated stock, plus they reduce growth. The older ones would reduce quality, too.”

Today’s growth regulators have various end-uses. In grasses, they can reduce grass stress by directing growth into a root system, stymie growth of the annual bluegrass weed (Poa annua), and uniformly stunt overall growth. In plants, a regulator can eliminate fruit production among ornamental trees and encourage fuller, more compact growth in shrubs.

Modern PGR chemistry inhibits the hormones that cause elongation of a stem. The result is slower growing grass or more compact plants that may be darker green than usual because the growth energy is redirected from plant extension to chlorophyll production. “The chemistries of PGR vary depending upon what you are trying to achieve,” says Formby.

Branham notes that PGR development and bioengineering are complementary sciences. “We breed grasses for short stature, but not for slow growth. We breed grasses for continuous quality performance, but when we chemically regulate grasses, we let the grass grow only when we want it to grow. There are times when grass has been injured or has had a lot of foot traffic on it and you want it to grow.”

When you want golf balls to bound ahead on fairways or roll straight on putting greens, regulating the height of grass becomes critically important. It is no wonder that golf course management professionals are keen on using PGRs. “There is no reluctance on the part of golf course superintendents to use Primo on putting greens,” says Dean Mosdell, a technical manager for Syngenta, manufacturer of the Primo MAXX turf grass regulator used widely on golf courses.

Reduces clippings

However, other segments of the landscape and lawn care industry have not as enthusiastically embraced PGRs.

“Where we have seen the greatest acceptance is by full-service lawn care operators. They fertilize and mow a property and they have a lot more grass and clippings to deal with if they are not using PGRs,” observes Mosdell. He adds that educating a homeowner (or a landscaper, for that matter) about the benefits of plant growth regulators is critical to increasing PGR usage.

“There is an education process involved. This is an add-on service provided to property owners and you have to explain the benefits. You have to explain that it is not a one-time application, but must be applied three to five times a season to reap the benefits,” he says, noting that the conversation can be more difficult when a property to be treated is, say, a modest residential yard.

“Unless a homeowner can quantify the benefits, he may not want to pay for the service,” says Mosdell.

Some commercial landscape maintenance firms operating on 12-month contracts employ growth regulation treatment without asking.

“When clients sign a contract, they essentially say they don’t want to have to worry about when to trim or spray a weed or mow the grass. They expect us to do it at the right time. They leave everything to us,” says Kelly Pope of Pope Lawn Care & Landscaping in Jonesboro, Ark. “So PGR is part of our program, more on plants than lawns. If we can slow the growth of plants and thicken them up and don’t have to trim them as many times in the growing season, it helps our labor costs.”

One of the chief business benefits of PGRs is reduced labor cost. Even so, Pope says that he and other green industry association members in the Jonesboro area use PGRs “sparingly,” at least compared to their use by golf course superintendents.

Manufacturers of PGR products report that overall usage is up. However, a brief survey of professionals in the country suggests that selective use of regulators seems to be the rule among many landscape and lawn care professionals.

Spotty acceptance

Kevin McIntyre of Buckeye Landscape in Columbus, Ohio, reports “very, very minimal” use of PGRs. “We have used some regulators on a hillside, but, honestly, we very, very rarely use it.”

Paul Salzmann of Salzmann Farms in Elberta, Ala., says he uses regulator chemicals “very, very little.” That seems reasonable because the enterprise wants to grow sod for homeowners and sports turf applications across the Southeast. Yet Salzmann has used a PGR to thicken a stand of grass or to prepare it for transplant. “But, in general, if you use a regulator, you won’t ever harvest the grass,” he says, a backhanded endorsement of PGR’s effectiveness.

Zach Chandler of Southern Heritage Landscaping in Birmingham, Ala., contracts with a licensed PGR applicator to treat screening shrubbery on commercial properties. The application has reduced his maintenance overhead.

“I started putting the growth regulator on Elaeagnus shrubs and now I only have to cut them back every 45 days. I prefer paying the applicator’s small fee rather than a large fee on labor to trim the shrubs and haul off the clippings,” he relates.

The chemicals in the treatment generally are not an environmental concern because of their short half-life. Build-up is negligible and runoff produces virtually no residual effects, according to manufacturers.

Even so, Branham, the University of Illinois professor, adds that too much of any chemistry can be problematic. Still, no incidents of adverse environmental impact have been reported, nor specific misgivings voiced.

A plant growth regulator is not a placebo, to be sure. It aggressively alters growth. Formby, the SePro technical specialist, reminds his Gulf Coast customers in Texas not to put SePro Cutless on ultra-dwarf bermudagrass. “The grass has been genetically modified not to grow tall and Cutless modifies growth chemically. If you put it on the bermuda, it won’t grow for about a month.” Stunting the growth of grass for a month is not the worst thing that could happen, many homeowners might quickly add.

Various turf grasses do grow at different rates, however, and react differently to chemical growth regulation.

Consequently, marketing of a one-application, season-long regulator is “a pipedream,” Mosdell says. “There is no new PGR on the horizon. The present regulators fill current needs and it is expensive to introduce a new one unless there is an evident need.”

Giles Lambertson is an experienced researcher, editor and writer who lives and works in Winchester, Kan.