By Philip Barbara

WASHINGTON (Reuters) - Decorating the playing fields at Major League Baseball (MLB) parks has become high art with groundskeepers using mowers and hoses to painstakingly fashion elaborate logos and patterns in the grass.

At the Washington Nationals new ballpark, the team's curly W logo shines in the outfield. At Fenway Park in Boston, the world champion Red Sox display a pair of socks and at Houston's Minute Maid Park the Astros show a star shooting through the state of Texas.

The patterns are not carved or burned into the grass. Rather, the groundskeepers carefully cut the grass in opposing directions so it lies at different angles that create contrasting shades of green when sunlight or the ballpark's massive floodlights reflect off the field.

"The patterns you can make are limited only by your imagination," said Dave Mellor, the chief groundskeeper at Fenway, where he has created images of the socks and Boston's stylized B in the outfield and infield.

Mellor, who first created playing field designs in 1993 when he was with the Milwaukee Brewers and is now something of a groundskeeper guru, has also created a figure 9 to honor Red Sox great Ted Williams's uniform number, an American flag on the anniversary of September 11, and the name "Bruce" when rocker Bruce Springsteen played at the old ballpark.

"We have an opportunity to capture a moment," he said.

The Washington Nationals' curly W is the newest logo to attract interest, with fans, journalists and one television baseball commentator wondering aloud about how it was done.

"It's a matter of training the grass and the way the light reflects off it," said John Royse, the team's grounds crew supervisor.

PARALLEL STRIPES

Before each game, members of the groundskeeping crew groom the outfield with a $50,000 sit-down mower that has five "reels" or rollers fitted with blades. They mow six-foot (1.8-metre) wide stripes between the infield and the outfield wall -- parallel stripes that radiate out from or toward home plate. In this way the grass remains swept in one direction or the other.

When sunlight or floodlight strike the grass, a darker shade of green reflects from the grass swept toward home, a lighter shade on the grass swept away from home, Royse said.

Then Royse heads for the outfield with a one-reel powered push mower to sharpen the curly W image, always taking note of the way the grass lies.

"It's like a dance," he said. "I go up, turn sharply and go down. I have to know my way around."

The type of grass is important. As the Nats' park was going up last winter, the club wanted a turf that would withstand Washington's subtropical climate but also could be aesthetically pleasing, said Royse.

Kentucky bluegrass was chosen over the Bermuda grass of the club's former park, RFK Stadium, because it was easier to manipulate and its blades had a waxier and therefore shinier epidermis, he said.

"With Kentucky bluegrass, it's easier to make designs," he said.

TURFGRASS DEGREE

Just before opening day in late March, the curly W was first created with the help of a specially made plastic template. The template had not been needed since, Royse said.

The curly W fades when the Nats are on the road and the grass is not cut every day. But Royse, who earned a bachelor's degree in "Turfgrass Science" from Penn State University, marks reference points in the design with a spray gun and water-based dye. He refreshes the image when the Nats return.

Mellor said he rotated patterns every 10 to 14 days at Fenway to alleviate wear and tear from a mower's turns in the grass. With some patterns he also shot water from hoses for finishing touches.

The league required that turf art should not distract ballplayers or compromise their safety, said Mellor, who has written books about how to create lawn art at home.

Many baseball teams are selling naming rights to their ballparks to bring in more revenue but Mellor does not want to see corporate logos emblazoned on athletic fields.

"A corporation would want its logo done in a certain way and that could hurt the grass," he said.

(Editing by Clare Fallon)