The concept of reducing the growth rate of grasses has been around for more than 50 years. The evolution of plant growth regulators (PGRs) began with their initial use in mowing reduction along roadsides and difficult-to-maintain areas.
Over time, they have evolved into precisely timed applications for seedhead suppression and the management of world-class putting surfaces. However, whether due to cost, lack of understanding, or concerns about precise application at very low rates, PGR usage has largely remained within the golf and sports turf industries.
But their utility doesn’t have to stop there. Growth regulators can be a valuable tool for turfgrass management in residential and commercial landscapes, as well as for ornamental plants and even arbor care.
Proper use of PGRs can help level the playing field for lawn maintenance companies facing rising fuel and labor costs—not to mention ongoing labor shortages. The most significant benefit is a reduction in mowing requirements.
In most cases, mowing frequency can be reduced by 40% to 60%, particularly on larger properties. The savings in fuel and labor alone can be substantial, and when factoring in reduced clipping management and lower emissions, the benefits add up even further.
One of the most used growth regulators is trinexapac-ethyl (TPac), sold under brand names such as Primo Maxx and T-NEX. This type II PGR works by inhibiting gibberellic acid (GA) synthesis, which reduces cell elongation and, consequently, top growth.
PGRs were initially classified into type I and type II chemistries—a simplistic system. Today, type II products dominate the market, further divided into six classes, many of which have herbicidal properties.
The key takeaway is that TPac reduces top growth while redirecting energy to root development and lateral growth. The result is a denser turf canopy with less leaf material removal and improved overall quality. This function minimizes mowing and clipping management.
TPac is safe for most grasses and can be used for full-property applications or as a banding product to reduce trimming around fences, buildings, and other obstacles. Many trinexapac-ethyl labels also include directions for mixing with turf paint on athletic fields, slowing growth to prevent mowing the paint off and reducing the need for reapplications.
Among type II PGRs, two classes are commonly used in turf management: class A and class B. Both inhibit GA synthesis, but they differ in where this inhibition occurs within the biochemical pathway.
Rebound growth—rapid top growth once regulation wears off—is more likely with class B regulators. While each product has its specific strengths and weaknesses, this distinction is a key consideration when selecting a PGR.
Edgeless was designed specifically to reduce trimming. It combines TPac and flurprimidol (Cutless), extending the period of growth regulation, particularly in high temperatures when TPac alone breaks down more quickly.
Edgeless can last up to 8 to 12 weeks, making it an excellent alternative to frequent string trimming. It also minimizes discoloration and concerns associated with non-selective herbicide use. The primary benefit? Less trimming, leading to savings in labor, fuel, and equipment wear.
Additional Plant Health Benefits
Beyond labor and fuel savings, PGRs provide several plant health benefits:
While PGRs have been widely used on turf for years, they are gaining popularity in ornamental landscape management. Trimming and pruning shrubs and other landscape plants is labor- and fuel-intensive, with additional costs for clipping disposal. In northern regions, one to two trims per year may suffice, but in warmer climates, frequent or even year-round shearing is necessary.
With ongoing labor shortages, maintenance companies must be strategic in managing their workload. Some businesses have resorted to eliminating high-maintenance plants altogether, resulting in revenue loss. PGRs can alleviate this challenge by reducing plant growth and trimming frequency.
Although not as widely used as in turf, many of the same active ingredients can regulate the growth of landscape plants, reducing the need for frequent pruning. Additional plant health benefits include:
The key question is: How much can PGRs save?
In terms of labor, fuel, and disposal costs, the savings can range from hundreds to thousands of dollars per month, depending on location and business size. Factors such as wages, fuel prices, equipment wear, trimming line usage, and disposal costs vary across the country.
However, in today’s economic climate, PGR usage in both turf and ornamental landscaping can significantly boost profitability.
For those interested in calculating potential savings, SePRO and PBI/Gordon offer online tools:
Additionally, a quick Google search will yield testimonials on PGR-related savings in turf mowing and water consumption.
Paclobutrazol (Pac-Low, Shortstop 2SC) has been used for years to manage tree growth and overall health. By shortening internodal growth, it creates a denser, fuller appearance. It also redirects energy to root growth and defense compound production, resulting in healthier plants. Additional benefits include:
In utility management, paclobutrazol is extensively used to prevent trees from growing into power lines. Because tree foliage isn’t routinely mowed off like turf, the effects of growth control last longer—typically two to three years per soil drench application.
Some paclobutrazol formulations, including Shortstop 2SC, also have shrub foliar labels. Low-rate applications can regulate growth for two to six months, depending on the plant species.
The cost-saving benefits of PGRs are clear—less labor, fuel, equipment wear, and emissions. The plant health advantages are just as compelling. Now, businesses must determine how to rationalize the cost of implementation. While savings will vary, the potential for increased profitability makes PGR usage a game changer for many in the industry.