To most people grass is just grass, the way that snow is just snow to anyone who lives below the Arctic Circle. But to people like Clark Throssell, grass comes in innumerable varieties, with quirks and character that only a devotee of turf would care to notice. Throssell, who recently became director of research for the Golf Course Superintendents Association of America, spent years studying specialty grasses at Purdue University. Stooping over a plot of creeping bentgrass there, he explains why it's the plant of choice for putting greens: It can tolerate being mown to an eighth of an inch. But it makes lousy footing for football fields, because when it gets too long it doesn't stay stuck to the ground. He tugs on a fistful to demonstrate, and it lifts off the sod like a bad toupee.
"When it gets above half an inch, it's a weed," says Throssell.
Among the thousands of grass species, only a few dozen have what it takes to make turf. A good turf grass must withstand traffic— it has to be sturdy and grow fast enough to sustain the abuse from cleats, golf carts, sneakers, and strollers. It has to tolerate mowing, whether it's a weekly lawn cut or a daily putting-green buzz cut. It has to show some resistance to disease, insect damage, and drought. It has to look good: Ideal turf grasses have dense, narrow blades that grow straight up. And even amateurs know that turf grass must be very, very green.
Turf enthusiasts have been cultivating grasses to meet these specs for centuries. Today about a dozen species dominate the landscape in the United States, with Kentucky bluegrass the most widespread among them. But concerns about the environmental toll of turf maintenance are challenging the hegemony of Kentucky bluegrass and its cohorts. Turf managers are under increasing pressure to limit irrigation, pesticide and fertilizer runoff, and mower emissions. In response to these pressures, turf-grass experts are developing grasses customized for certain climates, soil types, and uses.
One example is seashore paspalum, a warm-season grass from South Africa and Australia that probably made it to the coast of the southeastern United States as bedding on slave ships. In the wild, paspalum grows on dunes and shorelines, watered only by occasional ocean flooding. In trials at the University of Georgia at Griffin, the grass needed only half as much water as Bermuda grass, a southern mainstay.
Like seashore paspalum, the most popular turf grasses are imports from other continents— Kentucky blue-grass, for example, actually hails from Europe. Some breeders are now turning to native grasses in the hopes that they will have better defenses against endemic diseases and thus may re-quire smaller amounts of pesticide. Doug Brede of J.R. Simplot Turf and Horticulture in Post Falls, Idaho, introduced a hardy native bent grass several years ago that has demonstrated surprisingly strong resistance to a fungus called brown patch.
"There are areas where the mainstream grasses just don't cut the mustard— too much wear, too much water, too much shade," says Brede. "And you know there must be something in nature that will fill that niche."
A cool-season bluegrass called Poa supina might literally fill a niche on northern athletic fields. Like many grasses, supine bluegrass spreads with aboveground shoots called stolons. But because its stolon growth is faster and more tenacious than Kentucky bluegrass's or ryegrass's, it can infiltrate worn areas in front of goal cages and in midfield that normally have to be patched with sod or reseeded. And traffic won't keep it down: In studies simulating playing-field wear and tear, supine bluegrass out-competed Kentucky bluegrass, spreading from 5 to 50 percent of the field area in just one year. After three years, it covered 95 percent of test plots.
But for every advantage a certain grass offers, there are drawbacks. Supine bluegrass, for example, may not be green enough for some grass connoisseurs. "Americans have the idea that if it's light green, it isn't healthy," says Kevin Morris, president of the National Turfgrass Federation in Beltsville, Maryland.
That's where breeding comes in. By repeatedly crossing plants with the darkest color, turf breeders can improve the appearance of a grass like Poa supina in just a few generations. A fine-leafed standard called tall fescue, for example, has so benefited from decades of breeding that it scarcely resembles its ancestor, a coarse-leafed pasture grass. To get resilient grasses, turf specialists sometimes let nature do the breeding for them, combing cemeteries, parks, roadsides, and old estates for strains that may have survived decades of abuse or neglect. One of Brede's colleagues found Idaho bent grass on a Superfund site upstate. He says its tolerance of heavy-metal contamination may suit it for mine-reclamation projects.
Seeds from new or newfound varieties can be sent to the Turfgrass Federation for inclusion in the National Turfgrass Evaluation Program, which distributes hundreds of cultivars a year to land-grant universities in the United States and Canada. Participating institutions test each subject with methods such as pH shocking, trampling, drought simulations, mowing trials, and weed invasions. Only the strongest survive, and test results are posted on the federation's Web site.
Meanwhile, agrochemical companies like Scotts and Monsanto are going straight to the grass genome to get results. Genetically modified turf might produce its own pesticides, flourish in the winter, or grow more slowly, reducing the need for mowing. These projects have already drawn fire from activists who see grass as the obvious target for a not-in-my-backyard backlash against genetically modified crops. Conventional turf breeders have also expressed skepticism about the promise of genetic engineering. Unlike other commercial crops, Brede points out, grass is a perennial. So genetically modified lawns are going to be harder to contain than such seasonal crops as genetically modified corn, and the economic exchanges involved are going to be trickier than a farmer's yearly outlay for seed.
"No one's figured out whether home- owners would be willing to send in a check every year for the privilege of having a genetically modified lawn," he says. "I doubt that they would."
But stranger things have probably transpired in the quest for the ideal lawn. In that regard, turf breeders, agrochemical companies, and obsessed homeowners might agree: The grass could always be greener.
For a smorgasbord of links to educational and commercial turf Web sites, visit www.turf.uiuc.edu/turflinks/tl-1.html.
