The notion of reducing the growth rate of grasses has been around for over 50 years. The evolution of plant growth regulators (PGRs) began long ago from their original use of mowing reduction on roadsides and difficult areas to intricately timed applications for seedhead suppression and world-class putting surfaces.
Whether it was cost, lack of understanding or fear of accurate applications with very low rates, usage has largely been relegated to the golf and sports turf environment. Their utilization doesn’t have to stop there, however. Growth regulators can be an important tool for turfgrass management now and in the future in residential or commercial turf environments, along with landscape ornamentals and even in arbor care.
Proper PGR usage can help level the playing field for lawn maintenance companies with regard to elevated fuel and labor costs, not to mention the lack of willing workers.
The biggest “aha” moment comes with the reduction of mowing requirements. Generally, the reduction should land in the range of 40% to 60%, particularly when used on larger properties. While the savings there should be significant in terms of fuel and labor, add in clipping management and reduced emissions, and the benefits start to add up.
One of the more commonly used growth regulators is Trinexapac-ethyl (TPac), better known as Primo Maxx or T-NEX and many others. This product is a Type II PGR, which reduces top growth by inhibiting gibberellic acid (GA) synthesis, resulting in reduced cell elongation.
Some time ago, PGRs were classified into Type I and Type II chemistries, which was overly simplistic. While Type II products have become the predominant products used today, they’re split into six classes, many of which have more herbicidal characteristics.
That’s a lot but the take-home message is, this chemical will reduce top growth, redirecting energy to root development and lateral growth. The result is a tighter turf canopy with less leaf material removal and better overall quality.
This function reduces mowing and clipping management. T-NEX is safe for most grasses and can be used to treat an entire property or as a banding product for reduced trimming around fences, buildings, and other areas. Most Trinexapac-ethyl labels also will have labeling for turf paint mixtures on athletic fields, slowing growth to reduce mowing the paint off and reducing the need for reapplications.
Going back to the classifications of Type II PGRs, there are two that are commonly used in the turf realm—Class A and Class B. Both of these classes consist of materials that inhibit of gibberellic acid (GA) synthesis, but there is a slight difference.
TPac and Aneuw (NuFarm’s Prohexadione calcium) are late-stage GA inhibitors. Class B or Cutless (Flurprimidol) and Trimmit (Paclobutrazol) are both early-stage GA inhibitors. All this means is that when in the pathway of GA synthesis the inhibition takes place. This fact is important in terms of storage of produced carbohydrates in the early stages. Late-stage GA inhibitors will allow for carb distribution to the roots, resulting in less rebound growth. This is just as it says. Plants under growth regulation can experience some rapid top growth as they come out of regulation and that is much more likely to occur when Class B regulators are used. While many of these products have more specific strengths and weaknesses, that is the primary difference between Class A and B.
Edgeless was designed to reduce trimming. It is a combination of Tpac and Flurprimidol, better known as Cutless. It is well documented that TPac does breakdown more rapidly in the plant as temperatures rise, so combining it with another chemistry can extend the time of control.
In fact, Edgeless can last for up to eight to 12 weeks. It can be used anywhere a string trimmer goes and also will reduce the discoloration, unsightliness, or trepidation over non-selective herbicide usage. The overall up shot is reduced trimming, which directly relates to less man-hours, fuel consumption, and equipment fatigue.
The upside of PGR usage doesn’t end there. Plant healthcare benefits also should be considered. As mentioned, growth regulators help promote more lateral growth, which will shade the soil surface helping to crowd out weeds and reducing sun penetration leading to water loss and preemergent barrier breakdown.
Additionally, by regulating leaf growth, they can reduce water loss from the plant, improving drought tolerance. They do all of this while improving rootmass development and color.
Again, these products have been used on grasses for years but more recently they have found their way into management of landscape ornamentals. The trimming and/or pruning of ornamental plants is a reality for many maintenance companies. These processes tend to be extremely labor- and fuel-intensive, not to mention the costs of clipping disposal.
While more northern parts of the country may only require one to two trimmings per year, southern regions may easily see several or even year-round shearing. Lack of willing labor continues to make processes like these far more difficult. Staff shortages continue to plague the industry, requiring companies to be strategic about what properties they take on.
In some cases, other maintenance operations have to be halted just to complete shrub trims. The use of lower-maintenance plants or elimination of others has become more common to streamline routine maintenance, the results of which add up to revenue loss for the maintenance companies.
The use of growth regulators for shrubs and ornamental landscape plants is not nearly as widespread as it is in turfgrass management. Many of the same active ingredients can and have been used to reduce the growth of landscape plants, alleviating the tedium of routine pruning.
Additionally, there are many plant healthcare aspects to take into consideration. Trimming is stressful and the reduction will lead to healthier plants. Other such benefits include more chlorophyll production (darker green color), enhanced flowering, and improved water efficiency and drought resistance. PGRs encourage a tighter, more compact growth habit for more aesthetic value and reduced wind/storm damage. While these materials reduce top growth, then can also redirect the plant’s energy into rootmass development.
There are a few of the same chemistries currently used, some just in different formulations. Cutless has been available in a granular form which requires irrigation for incorporation. The onset of regulation may take two to six weeks but growth suppression can last two to six months. In some markets, that may be the bulk of the growing season requiring just one application per year.
SePro has brought a new formulation to market named Cutless QuickStop. This is a liquid, sprayable formulation with more rapid activity. Regulation can be seen in as little as one to two weeks and immediate trimming needs reduced by 30% and up to 70%. Benefits of one application can last for several months. Thorough coverage is required as there is little systemic activity.
Atrimmec from PBI-Gordon is a liquid, sprayable option which also can reduce the need for shrub trimming by 50% or more. When applied right after the first trim or shape, Atrimmec can yield several weeks of regulation. In areas with a shorter season, one application may be enough, while other areas may require two applications. Again, as a sprayable, rapid effects can be seen but good coverage is required for even growth reduction.
The question always ends up being how much can these products really save? In terms of labor, fuel and clipping disposal, the answer can be hundreds to thousands of dollars per month. This is not a finite answer because wages, fuel costs, properties, equipment wear, trimming line (for turf) and disposal costs are different across the country, but in today’s climate, growth regulator usage for turf and ornamentals can mean a huge bump in your customer’s bottom line.
To help uncover potential savings, check out these calculators from SePro and PBI-Gordon. A quick online search also will yield testimonials on turf mowing and water consumption savings that can buoy the bottom line.
Lastly is arbor care. Paclobutrazol (Pac-Low, Shortstop 2SC) has been used for several years to manage tree growth and overall health. Shortening internodal growth will make the tree look thicker and fuller. It also redirects energy to the roots and defense compound production, providing for a healthier plant while increasing chlorophyll production which will give the tree a darker color and help to produce more carbohydrates. Another benefit is that it will induce the creation of a thicker cuticle or waxy leaf surface, which helps to protect the tree from some leaf-borne pathogens and insects.
All of these benefits are why I have included PGRs in tree healthcare programs. The difference is that because the foliage isn’t mowed off and lost like in turfgrasses, the cycle of growth control is much longer. Most would expect to see the duration of regulation to last two to three years with one soil drench application. This makes Paclobutrazol an extremely important tool in utility management, where it is used extensively to prevent tree growth into high-tension lines and other such areas.
Some Paclobutrazol products, including Shortstop 2SC, also have developed a shrub foliar label. Low rates can last two to six months, often depending on plant species.
The cost-saving benefits are clear in terms of reduced labor, fuel consumption, time, equipment wear, and emissions. The enhancement in plant health management is also clear—now it is time to rationalize the cost. Again, by conducting some easy internet searches one should be able to find more hard numbers on savings. While these advantages will fluctuate for every business, the end result should be amount to the next level of profitability, sometimes enough to be a game-changer.
Contact myself or Pat Gross, Ewing’s Tech Team, for more information on plant growth regulators, product availability and other questions. Email me at klewis@ewingos.com or call/text 480-669-8791. Email Pat at pgross@ewingos.com or call/text 714-321-6101. We’re happy to help.