New grasses offer aggressive growth for sports fields

A field of Regenerating Perennial Ryegrass (RPR) from Barenbrug appears thick and dense less than four months after seeding at Kuenzi Sod Farm in Salem, Ore. The grass holds particular promise for athletic field use, where aggressive growth and durability are critical.
Photo courtesy of Barenbrug USA, Inc.

Sports field turfgrass has to be able to stand up to extra wear and abuse and keep on performing.

Barenbrug USA recently introduced a new turfgrass, Regenerating Perennial Ryegrass (RPR), that was developed specifically to tolerate the wear of sports turf applications. This perennial ryegrass reproduces by stolons, aggressively spreading out to fill in any thin spots, an important trait when it comes to sports turf. After all, a full stand of turf provides a better, safer playing surface.

While the grass was unveiled in mid-January at the Sports Turf Managers Association conference in Florida, it took about a decade of research and testing to come to that point, says Christiaan Arends, turf product manager with Barenbrug. He says that RPR first attracted the attention of researchers conducting wear tolerance tests. “We were testing our grasses at a farm in Virginia, pulling a 2,000-pound ‘wear machine’ behind a tractor,” he explains. “At the end of the field, the unit has to turn around, and on that spot where the tractor turned around we started to see patches of grass growing and getting bigger and bigger.”

Figuring if that grass could survive, and even thrive, in the toughest wear environment where both the tires of the tractor and the huge wear machine were pivoting and sliding through the turn, researchers decided to examine it more closely. “We took the grass to our research farm in Oregon, and within a year the plantings were each 3-feet wide, which is very unusual for perennial ryegrass. At that point, we knew it was a very interesting material,” says Arends.

Since that time, the company has been testing the grass at a number of different university and private sites around the country to observe its quality and more accurately gauge its wear tolerance.

Arends believes that most RPR installations on sports fields will feature the grass as part of a mix with bluegrasses and perhaps other species. “We’re mainly eyeing the cool-season areas with this grass,” he states. Arends doesn’t anticipate interest among turf managers in the South to use the grass in seasonal overseeding. “It’s a higher-end product, and it’s aggressive. Most managers don’t want too much aggressiveness in their ryegrass in the spring when they’re trying to transition it out.”

Testing in transition sites, such as Virginia and Kentucky, show that RPR performs well in areas where there is both heat and cold conditions. In addition to sports fields, it’s also been tried in golf course and driving range settings, which also demand the ability to handle wear and tear. “There is quite a broad range of areas where the grass can be used,” says Arends.

In terms of water use, research thus far shows that RPR is about average for perennial ryegrasses, and entophytes give the grass good protection against diseases and pest threats. Arends says the grass shouldn’t require any more mowing than more traditional perennial ryegrasses. “It grows aggressively, but it’s more of a lateral aggressiveness, rather than growing more upwards,” he explains. “So the maintenance should be about the same.”

In addition to being available as a seed, RPR is being grown by a number of sod farms in various parts of the U.S. and will be available as a branded product. “We’ve had quite a bit of interest already,” says Arends. “The ability of the grass to fill in areas is really neat.”

While it’s the wear tolerance and aggressive growing nature that has sports turf managers most excited, RPR has other attributes that those playing on the fields will appreciate: the dense, durable grass promises to offer better footing and traction, leading to good playing conditions and athlete safety. “We’re also doing tests with sod farms to see if it can be grown without netting. We don’t have the results yet, but if it can be grown without a net, it might also be safer for the players,” Arends adds.

Other grasses that are gaining popularity among sports field managers are hybrid bluegrasses, often a cross of Kentucky and Texas bluegrasses. Dr. Tony Koski with the Colorado State University Extension reports that hybrid bluegrasses generally form extensive underground rhizomes. “Different from roots, rhizomes contain growing points that produce new grass plants. Grasses that produce rhizomes are better able to tolerate traffic and will recover more quickly from traffic-induced wear, often without the need to reseed the worn areas. An aggressive rhizome system also means better traction in a sports turf situation.”

Koski also observes that because these grasses can handle heat and stress, they often can be mowed at lower heights than traditional Kentucky bluegrasses. “This can be important for ‘showcase’ sports turf applications,” he explains.

One leading example is Thermal Blue, from Scotts Proseed. As its name implies, the grass is touted for its ability to handle high heat, which straight Kentucky bluegrass often struggles to do. Because it can tolerate higher temperatures, Thermal Blue helps sports turf stay healthy and able to stand up to wear and tear, even when the heat is on.

“The grass is very aggressive and throws out a lot of rhizomes, so the wear tolerance is very, very good,” says Wayne Horman, director of Scotts Proseed. “That doesn’t mean you replace other bluegrasses in a mix; diversity is a good thing, and there is no one perfect grass. You need the qualities of the other grasses, as well.” He often recommends a mix with 20 percent Thermal Blue. Because it’s so aggressive, this ratio ensures it won’t quickly take over the other grasses. Often, hybrid bluegrasses such as Thermal Blue are medium green, and incorporating other, darker species also helps with color.

Horman says because the bluegrass is heat tolerant, it is not susceptible to Pythium. Sports turf managers whose only window to overseed comes in the middle of summer, between soccer and football seasons, for example, can take advantage of the fact that this bluegrass actually prefers warmer soils for establishment. There are some areas that get too hot even for Thermal Blue; Horman cites places like Florida as being too hot and humid. However, in areas such as Atlanta, when combined with tall fescue, Thermal Blue produces terrific results. He cautions that in hotter, southern climates, the grass will require a little extra water to help cool itself and survive extreme temperatures.

Horman says there “probably is a little more mowing required with Thermal Blue,” but points out that is a small price to pay for increased wear tolerance and aggressive growing: “Unfortunately, you can’t have one without the other. You can’t have recovery without good growth.” The grass also can produce thatch, and while those managing home lawns or fine golf turf may not appreciate that fact, Horman says, “I’ve never met one sports field manager who has complained about thatch.” Thermal Blue also boasts a good “sheer strength,” which helps cut down on slips and slides, he adds.

Other examples of hybrid bluegrasses include Bandera and Spitfire, both from Seed Research of Oregon. “They offer improvements with heat and drought, and the strong rhizomes really help in high-wear areas,” says Mike Hills, regional sales and technical agronomist with Seed Research of Oregon.

Hills says that part of the challenge in producing hybrid Texas-Kentucky bluegrasses is seed production, with many research varieties producing little or no seed, or that seed having germination problems. “They’re both Poas, but they’re different species, so sometimes when you’re crossing them you get a lot of fertility issues,” he explains. Many grasses had to be abandoned during research trials, with only a few ever making it to market. Those that have, he says, perform well but still are not prolific seed producers. “That’s what makes all of these grasses relatively expensive, generally anywhere from $2.50 to $3 a pound on the wholesale market,” Hills adds. He says the high cost has unfortunately limited the use of hybrid bluegrasses on sports fields at the municipal and high school levels, where wear tolerance might be most critical.

Thermal Blue, a hybrid bluegrass from Scotts, can tolerate higher temperatures, helping the turf stay healthy and stand up to wear and tear on athletic fields.
Photo courtesy of Scotts.

Like Horman, Hills advises that hybrid bluegrasses should be used as one part of a mix rather than as a stand-alone application: “Any of the Texas bluegrasses can be susceptible to certain problems at certain times of the year. We like to promote them as part of a blend with other bluegrasses; that way the strong rhizomes of the Texas bluegrass can offer improved wear resistance and ability to recover, while the other grasses can mask some of the issues that might be seen with it.” Summer patch and cool weather growth (slow growth in fall or spring) are some of the common challenges that hybrid bluegrasses may present.

Mixes with hybrid bluegrasses and tall fescues have also proven successful in sports fields and parks, says Hills. Often, the hybrid bluegrasses are included as 10 percent of the mix in those applications, or at least part of a 10 percent bluegrass component.

Development on hybrid Texas-Kentucky bluegrasses continues, and Hills thinks the coming years will result in even more performance improvements. “The hope is that a seed yield increase in the next generation will help to bring the cost down,” he says. Even today, though, sports field managers struggling with high wear may well decide its better to pay a little more for the durability and aggressive growth of hybrid bluegrasses than to live with bare spots.

Patrick White is a freelance writer and editor who has covered every aspect of the green industry in the past 13 years. He is based in Middlesex, Vt., and is always on the lookout for unusual stories.

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