Columbia Nursery. 1903 Martha's Rd., Alexandria. Prices: $7.50 to $55. Call 768-7800 for directions.

Art and Anita Frazer call their sprawling acre of Alexandria backyard the Columbia Nursery. The name refers not only to their 20-year-old horticulture business but also to the attention they lavish on the plants in their care -- an estimated 10,000 azaleas, representing more than 300 varieties and uncountable colors and sizes. "We raise the plants from little cuttings on up, and we take care of them as if they're part of our landscaping," says Anita Frazer, who takes turns with her husband escorting visitors down the gravel paths that line their azalea beds. "We put a lot of care and sweat into these plants," she says, and their investment of effort has made them demanding caretakers. The couple nurtures their plants in a cold frame from tiny cuttings and later transplants them into the ground. At age four or five, after the plants have bloomed and shown their true colors, they're offered for sale. The Frazers dig each plant up as the customers wait and pack it in damp sawdust to lessen the shock of the move. Columbia Nursery should be at its best now, with most of its azaleas in full regalia. Even out of season, the Frazers can show you the splendid colors of their azalea collection from a portfolio of slides.