Lilypons Water Gardens. South of Frederick, Md., off I-270. For directions or a catalogue, call 301/874-5133.

The seasonal clock has come full circle again. The waterlilies are just beginning to take root in the ponds that stretch out over the 300 acres comprising the Lilypons Water Gardens. In another corner of Lilyponds (population: several million goldfish), experts are culling through tubs of goldfish to select those privileged to breed. The spring exercises have become predictable here during the 62 years the Thomas family has been growing what it calls the world's largest selection of ornamental fish and hardy and tropical waterlilies for backyard water gradens. Visitors often travel to see the gardens at Lilypons, June and July being the peak blooming season. But many customers order through the catlogue, receiving their purchases (goldfish included) trhrough the mail. "Waterlilies have virtually universal appeal," says Charles Thomas, "but you can't grow them unless you have a pool." So Lilypons sells garden pools (from 24 inches to 13 1/2 feet wide) and statues and fountains to ornament them. Lilypons is well worth a visit, to see the lilies or even just the countryside. CAPTION: Illustration, no caption, By Robert Soule