This article was reprinted with permission from the National Association of Landscape Professionals. Attend ELEVATE, their national conference and expo for landscape and lawn care professionals in Dallas, TX, on September 10-13, 2023.
The Benefits
Plant growth regulators (PGRs) can be used on both turfgrass and plants like ornamentals, shrubs and trees. In the case of regulating turfgrass, PGRs reduce mowing frequency. Matt Giese, a technical services manager for Syngenta, says that properly used PGRs also increase turf color and turf quality of a healthy, actively growing lawn.
“Using PGRs can also support reduced water use to maintain the quality of the turf, potentially providing an environmental benefit in arid climates, during droughts, and when water use is limited or restricted,” says Jamie Heydinger, lawn care segment lead for Nufarm.
“When used on shrubs, landscape companies can enjoy fewer pruning cycles, less green waste, less fuel consumption, fewer dumping fees, less disruption to the property, less wear and tear on equipment, less wear and tear on laborers, improved safety for workers by reducing ladder usage,” says Emmett Muennink, an Arborjet South Central technical manager.
“The number 1 benefit is reducing labor costs, especially overtime pay,” Muennink adds. “We all know that time is money. PGRs can reduce time spent maintaining a property. Secondly, treated shrubs keep a manicured appearance. The shrubs will also look healthier due to physiological changes that occur as a result of growth inhibition. Growth-regulated shrubs often have darker green foliage, enhanced flower set, improved drought tolerance, and are less susceptible to foliar diseases.”
The Drawbacks
The main drawback of PGRs is if the turf is over-regulated, it can become stressed and vulnerable to diseases. “PGRs are great tools to reduce unnecessary growth that will just be mowed off, but turfgrass must produce some new growth to recover from the environmental stresses (such as extreme heat and drought) as well as foot traffic but also stress from pest pressures like insects and diseases,” Heydinger says.
Giese adds that discoloration can occur after the first application or if the turf is under stress. “A small amount of water-soluble nitrogen or chelated iron added to the spray solution can mask the discoloration and the plant will grow out of it in a few days,” Giese says.
Scott notes that there is a rebound effect with PGRs where the plant stores energy and gets a flush of growth after the regulation wears off. He says you have to be strategic about how you use these products and the rates at which you use them. There are tools available for landscape professionals to map out and plan how they’re going to implement PGRs into their programs.
“They could use plant growth regulators to reduce the amount of mowings that are required as they take on some of those other jobs that they maybe would not be doing throughout the summer,” Scott says.
Muennink acknowledges that an additional challenge of applying PGRs is they can add to an already busy spraying schedule. “Also, the applicator must get uniform spray coverage, and be careful with overspray to non-target plants in the landscape,” Muennink says. “Variance in spray coverage will impact the performance of the PGR.”
Common Misconceptions
Muennink says one misconception is that the product cost outweighs the benefits of the applications, but companies are seeing dramatic savings in labor costs that outweigh the product cost. He says people also assume PGRs are easy to misuse, but he says following the label instructions and talking to the product representative will eliminate this risk.
“A common misconception is that the turf is not growing when under regulation,” Giese says. “While vertical growth may be suppressed, the plant continues to carry on normal plant processes to grow laterally and in root growth. Landscape professionals should continue normal cultural and fertility practices similar to that of non-regulated turfgrass.”
It’s also important to understand that PGRs are not herbicides. While they can regulate weedy grass species like Poa annua or Poa trivialis, an application will not kill them outright. “Not all PGRs will regulate a weedy species more than the desirable species, which would not provide a competitive edge,” Heydinger says. “Growth regulating PGRs overall could be used to spot treat weedy grasses that grow in patches at high rates to encourage takeover by desirable species.”
Advice For Others
Taking your time to research PGRs first is critical if you want to be successful with these products. “It is definitely not a category you want to jump in and expect to not do much research and make an application and think that you’re done because there are there are some adverse effects that can happen,” Scott says. “For instance, in a turf setting, you can get overregulated, where essentially you completely shut down the plant.”
Heydinger says landscape professionals should familiarize themselves with the top PGRs and connect with suppliers on educational resources on those products to learn when and where they work best, what is recommended and what chemistries are compatible.
“Research which PGRs are most effective on the target turf species and what that turf species looks like under regulation is important when choosing to spray PGRs,” Heydinger says. “It will also be important to understand how to best integrate PGRs into your spray and turfgrass management program as application timing (time of year and even time of day), rates and reapplication timing all play a part in achieving an effective and healthy amount of growth regulation.”
Giese advises establishing a comfort level as the rates and timings for different turf species can vary. “Start out with a small area at a low to middle range rate of PGR and familiarize yourself with the response and length of regulation,” Giese says. “Adjust rates and timings as needed to match your desired results.”
Muennink also agrees trying is the best way to see if it’s a good fit for your operations. “Select a property that is a maintenance nightmare and try it out,” Muennink says. “Just make sure your maintenance team knows not to prune the shrubs after the application. Make notes and compare how many shearing events you were able to skip by using the PGR. Try it out on various shrub species so you can learn how the product performs.”
Odom is the content manager for the National Association of Landscape Professionals (NALP). NALP represents nearly 100,000 landscape industry professionals in the U.S., Canada, and overseas. Member companies specialize in lawn care, landscape design and installation, landscape maintenance, tree care, irrigation and water management, and interior plantscaping. Members also include students, consultants, industry suppliers, state associations and affiliate members. To learn more about the benefits of membership, click here. For the original article, click here.
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