Stiles Colwill, a Baltimore designer and former museum director of the Maryland Historical Society, started gardening seriously 10 years ago when he inherited a 122-acre horse farm from his parents. "I just wanted to get rid of 45 rows of tomato plants my mother grew every summer for 50 years in her World War II victory garden," he jests.

But the real reason he went into high gardening gear -- once he and Jonathan Gargiulo, a partner in the New York antiques firm John Rosselli International, planned the first terrace -- was the beauty of the land. "We realized we wanted a garden in keeping with this farm," Gargiulo says.

A former 18th-century land grant and now a successful thoroughbred brood mare and foaling operation, Colwill's farm, called Halcyon, which means calm wind or good omen, has been in business since his parents purchased it in 1941.

Belmont Stakes winner Hail to All was foaled in one of the barns, and Colwill's father was a record-holding steeplechase jockey with three consecutive wins at the prestigious Maryland Hunt Cup.

When Colwill inherited the farm, Gargiulo encouraged him to push back fence lines to form lawn and gardens around the house. "The best feature of this whole property," Gargiulo says, "is the way the house sits right in the middle and fields sweep off in four directions to the edge of the forest."

Behind the house, a stone staircase leads down to the centerpiece of the garden -- a sunken, almost hidden terrace. Colwill played up the element of surprise with what he calls "outrageous floral colors." This sunken garden grows flowers and vegetables (started early in the farm's 20-by-50-foot greenhouse) for continuous summer use. "So many gardens are about color and texture today," says Colwill, "but we're after something more practical: fresh vegetables and flowers in colors we like for the house."

They each have their favorites, with Gargiulo claiming the brilliant zinnias and cosmos, spiderlike cleome, and heat-resistant dahlias and Colwill seizing on creative combinations such as cockscomb with red and green chard and harvard beets. British gardener Gary Baverstock introduced blue flowers to balance the hot-colored quadrants and used tall poled vines and beans to vary a plant selection limited by Maryland's hot summers.

More terrace development followed the success of the sunken garden. A terrace above the garden was designed to accommodate a party tent for the many outdoor parties the two men host. Eventually, three walled levels were completed, leading to half a dozen garden rooms.

Having cultivated what Colwill perceives as "a happy, manageable envelopment of the house," he and Gargiulo are now focused on creating year-round interest in the garden rooms. They delight in seeing trees they have planted maturing gracefully against the panorama. Thanks to their appreciation for the long view, horses will still be grazing the old pastures centuries from now.