The Biology of . . . Lawns

America's addiction to grass wastes billions of gallons of precious water every year. But a new kind of turf may help us kick the habit for good

By Alan Burdick|Tuesday, July 01, 2003
RELATED TAGS: AGRICULTURE

It's tough being turf. You get ripped up, mowed down, whacked, andtrampled—by cleats, lawn mowers, five irons, and linebackers the sizeof refrigerators. And that's only if you make it to the field. Everyyear, dozens of new grass varieties are sprung upon the Americanpublic: TifSport, Mohawk, Axcella, Princess 77, each one meant toconquer some fraction of the 30 million acres of lawn, golf course,athletic field, public park, cemetery, and sod farm in the UnitedStates.

Most of the new grasses are just genetic tweakings ofpre-existing models—the botanical equivalent of a "new and improved"paper towel. Once in a great while, however, a new grass surfaces thatpromises to reshape the turfscape. Ron Duncan, a turf scientist at theUniversity of Georgia, thinks he's onto one. Popularly known asseashore paspalum (Paspalum vaginatum to turf geeks), Duncan'sgrass is notable less for what it does than for what it doesn't do:drink much. It requires as little as half the water of some flashiergrasses, and it can subsist on seawater. "It's fitting into a nichethat hasn't been there before," Duncan says. "This is a grass whosetime has come."

Once upon a time, three or four decades ago,the turf industry had no niches. The goal was to findgeneralists—grasses that worked for most people in most places. It wasone-grass-fits-all. Then farmland gave way to suburbs, housingdevelopments, and fields of leisure: 50 million lawns, 700,000 athleticgrounds, 14,500 golf courses. Turf grasses were specialized: warmseason or cold season; arid, boggy, sunny, shady; lawn sod, golf sod,football sod. Turf today is a $45-billion-a-year industry. TheUniversity of Georgia alone has seven turf researchers studyingeverything from genetics and soil science to plant pathology, nutrientuptake, and insect management. An undergraduate can major in turf.

The field is dominated by a handful of tried-and-true species: Bermudagrass, fescue, Kentucky bluegrass, and a few others. There are morethan 200 commercially available cultivars of perennial ryegrass alone.Still, enterprising researchers continue to scout the world for newturf contenders. Forget virgin rain forests or remote tropical islands:Researchers comb parking lots, old parks, and highway medianstrips—"areas that really beat grasses up," one turf scientist says."They're looking for grasses that basically look like survivors." Oneformerly popular grass, Manhattan, was discovered growing wild inCentral Park. Another, Merion, was found on a golf course inPennsylvania.

Needless to say, not every grass makes the cut.The chief lawn grass criteria are fertility and "mowability": A lawnshouldn't grow too fast (otherwise it may require mowing more than oncea week), and when it is cut, it should come back neat and tidy, notfrayed and dead on the ends. Golf and sport turfs face stifferchallenges. Ideal golf greens should be soft and spongy, yet firmenough to give good "bounce." In one classic golf sod test, farm eggsare dropped onto turf candidates from a height of 11 feet to see howmany break. (None, ideally.) And there are stress tests. These rangefrom the straightforward—careering across a sod farm in a golf cart—tothe mechanically complex. With giant rollers and rubber-rod beaters,scientists simulate the umpteen body slams and foot falls turf may beasked to endure, not to mention the effects of the seeders, sodders,scarifiers, rock removers, and other machinery designed to maintain it.

"There's probably as much art as science in turf grassscience," says Kevin Morris, spokesman for the National Turf EvaluationProgram, a nonprofit organization that tries to standardize theanalysis of commercial grasses. "You have to understand the science,but the art part makes it fun."

The50 million lawns in the United States consume 270 billion gallons ofwater every week—enough to give everyone in the world a shower fourdays in a row. Each year, those lawns are slathered with 67 millionpounds of pesticides and mowed by machines that use 580 million gallonsof gasoline.

 

The hottest area of research, Morris says, is drought tolerance. Thecurrent generation of turf grew up on cheap fertilizers and limitlessfreshwater. No longer. Urban water shortages are more frequent, even intraditionally soggy states like Pennsylvania. By law, residents indesert areas of Los Angeles County can water their lawns only withrecycled dishwashing or bathing water.

 

Paspalum may beone answer. That grass can get by on as little as half the waterrequired by Bermuda grasses, not to mention only half to two-thirds theamount of fertilizer. In addition, Paspalum

feeds on awavelength of ultraviolet light that other turf grasses don't use,enabling it to thrive in shady or cloudy situations. "Imagine growinggreen grass in a domed stadium 365 days a year," Duncan says. "That'sthe next generation of grasses."

 

Duncan first came across Paspalumin 1992, when a colleague sent him a clump. It was dark green, waxyleaved, fine textured, and plain lovely. So Duncan read up. Varietiesof Paspalum vaginatum, he learned, thrive along coasts aroundthe world; genetic analysis revealed that it evolved originally inSouth Africa, then traveled to West Africa, South America, and theUnited States after the 16th century. Duncan suspects the grass spreadwith the slave trade; it grows on dunes and would have been readilyavailable as bedding. He has found Paspalum

growing in former slaving ports in eastern states.

 

Paspalum

owes its drought resistance to a combination of factors. Its roots areparticularly strong, so they can burrow into hard, dry soils, and theyare unusually good at drawing oxygen from compacted, oxygen-poor soils.But what sets the grass apart is its tolerance for salt. Every plantworks hard to maintain proper salt levels in the cytoplasm of itscells. Too much salt inside a cell degrades or destroys the enzymesnecessary for producing energy. At the same time, if too much saltcollects in the soil around the plant, a pressure differential arises,and water is sucked from the roots by osmosis. Some plants manage saltby blocking its uptake; others absorb it and spit it out later. But fewcan tolerate salinities much higher than 0.5 percent above freshwater.

 

That poses a problem. Cities in the South and in the West have begun torequire homeowners and golf courses to use gray water, such as thewater that runs out of a clothes washer or the kitchen sink, for lawns.It often is too saline for standard turf grasses. Golf courses alongthe coast contort themselves, protecting their turf from ocean spray. Paspalum,

in contrast, soaks up salt, then squirrels it away in little pouches,or vacuoles, inside its cells, walled off from the tender,energy-producing mechanics within the cytoplasm. Duncan has founddozens of varieties of the grass over the years, in mangrove swamps andlow-lying bogs; some can remain submerged under brackish water for aslong as a month.

 

From a burgeoning collection of Paspalumvarieties, Duncan has bred, crossbred, refined, and licensed twocultivars called Sea Isle 1 and Sea Isle 2000. For the past two years,the Houston Astros baseball team has played on Paspalum in its home stadium. A golfer can find Paspalum

on courses across all the tee-able continents. It's not too much of astretch to say that some of the world's most exclusive country clubsowe their success to the beds of slaves. (Augusta is not one of them.)

 

In return for all its admirable qualities, Paspalum

asks for only one thing: an occasional salt fix. Once a year, theHouston Astros' groundskeepers must lay on a micronutrient. "What itis, is Morton Salt," Duncan says. "You don't put much on, about thesame as what you'd put on your eggs in the morning." So let the gamesgo on—after the champion has eaten breakfast.

 

 

 

The University of Georgia's College of Agricultural and EnvironmentalSciences Web site has information on seashore paspalum, including listsof cultivars and photos of the turf in situ at golf courses throughoutthe United States: www.griffin.peachnet.edu/cssci/turf/paspalum/paspalum.htm

.

 

TheLawn Institute offers practical, extremely pro-lawn guidance to helpconsumers select and care for the grass beneath their feet and aroundtheir houses: www.turfgrasssod.org/lawninstitute/index.html

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The U.S. Department of Agriculture has tips for eco-friendly lawn care: www.nrcs.usda.gov/partners/for_homeowners.html.
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