Go ahead, kneel on the ground and get your nose a couple of inches from the pond. Smell that? It's a William McLane, a blue-purple variety of water lily whose delicate scent is an aphrodisiac, the staff at Lilypons says.

For $30, what more could one ask for? And here at Lilypons, supplier of aquatic plants for water gardeners from Potomac to Tokyo, there is more -- plenty more. Across 300 acres, millions of lilies are in full bloom this month, making Lilypons seem a slice of nirvana in Frederick County. A former fish farm, the Buckeystown business switched from fins to flora a generation ago, cashing in on an explosion of interest in water gardening.

The backyard-pond business has grown faster in recent years than a brood of tadpoles. The number of households with water gardens quadrupled, to 16 million, from 1998 to 2003, according to the National Gardening Association. Spending on backyard ponds more than doubled during that period, from $659 million to $1.5 billion.

Margaret Koogle, who represents the fourth generation of her family to run the business, remembers when her father, Charles Thomas, a lily hybridizer, made the switch. It was the 1970s, and the dawn of fiberglass and rubber liners suddenly had made backyard ponds, as well as backyard swimming pools, affordable to the middle class.

Back then, "The average pond size was 4-by-5 feet," says Koogle, 41. "Today, it's 10 by 15."

Lilypons was founded as Three Springs Fisheries by Koogle's great-grandfather, George Leicester Thomas Sr., in 1917. The business flourished as a goldfish farm, its stock nurtured on the limestone bedrock whose nutrients make this region an excellent location for fish hatcheries.

So many fish sloshed through the mail from here to five-and-dime stores across the country that the traffic overwhelmed the Buckeystown post office. In 1935, the business changed its name to Lilypons, after Lily Pons, the famed opera singer, and opened its own Lilypons, Md., post office. The post office was dedicated, of course, by the tiny, French-born soprano, who would send her mail to be postmarked there every Christmas until her death in 1976. The adjacent road, a nearby bridge and a coral pink, 100-petal lily are named for the singer.

Today, Koogle handles the business's books and hiring, and her brother-in-law Richard Koogle (she and her sister Victoria married brothers) is the vice president and director of operations. Another sister, Elizabeth Diaz, runs Lilypons' Web site.

Two-thirds of its business is mail-order, handled by a Baltimore-based call center. Lilypons sends 75,000 catalogues each quarter, and mails 700 orders a day during its peak spring-summer season. Orders are released according to a region's climate, so nobody receives a frozen fish in Minnesota in March or a boiled one in North Carolina in August.

The company won't ship fish during July and August because live arrival is guaranteed. Orders range from a single plant or koi to a Pond Jet 2400 lighted fountain system that costs $1,800. Lilypons gets its fish from other suppliers these days, but "we grow 80 percent of the plants we sell," Koogle says.

Everything Lilypons sells through its catalogue is available in its retail shop, set amid acres of former goldfish ponds now mounded with bog plants, multi-hued lotus and exotic lilies, like the night-blooming Longwood Hybrid, whose leathery pads grow up to five feet across in a single season. Koogle's family has a favorite photo of her sister Victoria, 37, as a baby, lying in the center of a Longworth lily pad.

One overcast morning last week, Jan and Tom Vaughan walked past the "retirement pond," where Lilypons houses fish that have outgrown their owners' tanks (koi can live for more than a century and grow up to three feet long). The Vaughans built a home in Lancaster County, Va., in 2000, and are finally ready to landscape their yard.

"We'd like a water feature we can hear from our screen porch," Jan Vaughan says. "Our landscape architect sent us here."

Wandering through the company's formal fountain gardens, Koogle says most people are attracted to water gardens "by the sound, the lilies or the fish," as opposed to the reeds, rocks, snails and seaweed-like, algae-cleaning plants that the business also sells.

Although ponds, when balanced correctly, are supposed to be self-cleaning, most people put in too many fish or too many plants, or the wrong combinations of both. Consequently, sophisticated filtering systems are big sellers, as is black dye that shades the water garden to hide algae and spotlight the colorful fish.

Chuck Finley of Monrovia is Lilypons's resident birder. "We've got 250 different species here," Finley says, handing over a roster. The exhaustive list includes the Great Blue Heron, which is marked "common," and the Loggerhead Shrike, marked "rare -- how lucky can you get."

The Frederick chapter of the Maryland Ornithological Society meets here annually. The club members, who Finley jokingly says "are a little touched in the head," stand all day in a 17-foot diameter circle, binoculars pressed to their faces, tallying the number of varieties they spot. The record is 84, though Finley says that birders, like fishermen, "all lie."

Finley was the commander of the Camp David Detachment of the White House Communications Agency in the 1980s. He says he got President Ronald Reagan interested in birding. It is Finley who, with military authority, orders visitors to drop and sniff the lilies.

He'll even hold women's handbags for them.

"I'm telling you," he said, "once they get that scent, they're sold."

Megan Stewart, 24, pulls Thalia foliage for winter replanting while working at Lilypons Water Gardens, a longtime backyard-pond business in Buckeystown.Besides plants, Lilypons Water Gardens sells such fish as koi, comets and shubunkin goldfish, which can live in the ponds while young.Proprietor Margaret Koogle and resident birder Chuck Finley stroll through one of the formal gardens at the 260-acre Lilypons facility in Buckeystown.Lilypons began as a goldfish farm in 1917, but now Koogle and her sisters, as fourth-generation proprietors, run the booming water-pond business.