A PGR Primer

Indispensable as an application and fascinating as a scientific curiosity, plant growth regulators (PGRs) have been making a splash in the lawn care market for their ability to help control the speed at which a plant matures.

The synthetic compounds are used, primarily, to slow or stop the growth of turfgrass and ornamentals by chemically altering the plants’ physiological make-ups. Not only can PGRs save contractors time by eliminating multiple mows, they also can curb the amount of clippings produced.

The hows and whys of any PGR’s specific abilities are best left to the scientists, but learning about the difference they can make in a company’s growing months are worth investigating.

THEY ARE WHAT THEY DO. "Plant growth regulators are products that are applied to turfgrass primarily to slow growth and improve turf quality," says Dennis Shepard, PGR research director, Syngenta Professional Products, Franklin, Tenn. "They slow growth by either slowing cell division or by slowing the production of gibberellic acid, the plant hormone that stimulates cell elongation."

"PGRs interrupt and regulate cell division, causing plants to either create larger, different shaped or more compact cells," adds George Raymond, business manager for herbicide/PGR, Bayer Environmental Science, Montvale, N.J.

This all sounds simple enough and it’s really all the science background a lawn care operator (LCO) needs before looking into how PGRs can help business.

"If an LCO has mowing or maintenance contracts that require a lot of labor to keep them going, sometimes the use of PGRs will knock down the amount of mowing, and that’s a big plus," Raymond says.

Control over growth allows LCOs to better manage their workloads by slowing the rate at which properties need to be maintained. "At the peak of the season, sometimes LCOs find themselves mowing the same properties twice a week," explains Doug Obermann, turf and ornamental products manager, PBI Gordon, Kansas City, Mo. "Some PGRs can be used to slow down this excessive growth so that they’ll only have to mow once a week. In the peak season, this could cut growth by about 50 percent."

"It can be a challenge keeping up with mowing cool-season turfgrasses in the spring when growth is optimum and rainfall normally occurs," Shepard adds, explaining that some PGRs allow LCOs to take on more customers because they can better manage mowing operations.

MINOR MIRACLES. PGRs also can be beneficial in reducing mower clippings since the cost of yard waste disposal has increased in many states, according to Raymond. "Fees have gone up because of city cutbacks," he says. "LCOs are looking for ways to reduce those costs – and PGRs do that."

PGRs can make an LCO more time efficient in other ways as well. For example, Obermann points to PGRs as a method for edging a property. "When PGRs are used for edging, you don’t have to string trim as much, therefore avoiding dead turf or visible soil at the lawn edges," he says, explaining that regulated edge growth is more attractive than normally string-trimmed areas. "There is still some green there."

According to Raymond, some LCOs also have been taking more notice recently of PGRs’ effects on seed-head production. He cites weed-like grasses such as poa annua as one type that can be controlled by using PGRs to suppress seed heads.

Obermann explains that seed heads expend energy on seed production that would otherwise go to turf roots and leaves. "Around mid-April – whenever peak growth is getting ready to happen – you’ll start seeing all of these seed heads popping out of the grass, which can look rather rough and messy," he explains, adding that seed head stalks make up a significant chunk of clippings volume. "But if you prevent that seed from forming by using a PGR, the plant doesn’t waste that energy. It also improves the quality of the grass."

TREAT IT RIGHT. Reaping the benefits of a PGR program, however, requires an LCO to consider some important factors specific to his or her company’s peak seasons and location.

"Generally, the spring is when PGRs get the most use – after the plants have come out of dormancy and are fully growing," Obermann explains, adding that the exact timing of this depends on an LCO’s specific region.

Shepard adds that PGRs should only be applied to plant material that is healthy and actively growing. "They should not be applied to plants that are drought-stressed or weakened by insects, diseases or wear-and-tear," he says.

In the case of turf, specifically, Shepard advocates PGR applications to both warm- and cool-season varieties throughout the growing season as long as the turf is in good condition.

However, because multiple formulations and brand names are available, familiarizing oneself with the recommended application for any particular PGR is essential. Like any other chemical application, each type of PGR is carefully labeled for its particular formulation and intended application. "Each formulation has its own characterization and a specific listing of what turf types it regulates," Raymond explains, adding that accidental misuse will most likely be either ineffective or damaging to the treated plant.

When applying PGRs, making a uniform application is crucial. "Generally PGR products are liquid and would be applied via broadcast spraying," Raymond says. "And they’re usually applied during the early growth period of the season and then periodically thereafter."

"To regulate ornamental. growth, PGRs are mixed with water and sprayed on plant material," adds Obermann, pointing out that uniform coverage and penetration are essential for PGRs to produce the desired effects. "If you just spray the outer branches with a light mist, you’ll slow the growth of a plant’s outer branches and stems, but you won’t slow the growth of the inner branches. This kind of erroneous application can lead to break throughs, where the under foliage grows past the surface foliage."

As a result, maintaining adequate and thorough coverage when applying PGRs is crucial, LCOs and PGR manufacturers recommend. For instance, Buddy Reid, division manager, Helena Chemical Co., Cuthbert, Ga., acknowledges that LCOs must be very careful about applying the product evenly. "If you don’t, you’ll have hills and valleys in the growth of the lawn," he says. "You also will have different colors in the growth of the lawn, which is no good for aesthetics."

"Application is very similar to herbicide broadcast applications, like the kind done for broadleaf weed control," Raymond says. "You’d generally cover the entire area in the same way you would with a fungicide or herbicide."

Even though most turf PGRs come in liquid formulations, Shepard says that granular PGR formulations do exist but are primarily used on golf courses. "Granular formulations of PGRs for turf may be developed in the future if the market demand for it exists," he says.

Raymond adds that many LCOs are experimenting with ways to combine products and different modes of PGR action to create new effects that he has seen successfully encourage dense and more uniform growth. And some PGRs, Shepard says, can be tank-mixed with products like fertilizers, iron, fungicides and insecticides, saving even more time during the application process.

However, as is true with any chemical application, labels should be carefully examined before an LCO decides to mix products. When used as indicated by the label and as instructed by professionals, PGRs can have a positive sweeping effect that can impact a property’s foliar vigor, density, color and general aesthetics, as well as add to a company’s work load, man hours, physical labor and, ultimately, the bottom line.

Will Nepper is assistant editor for Lawn & Landscape magazine and can be reached at wnepper@lawnandlandscape.com.