The lady came upon the crimson blossoms and gasped. "Ahhh, gee," she said. "I must get out my camera."

The other day at the United States National Aboretum, she was discovering the joys of something labeled "fireglow" in the Oriental plot of the herb garden. Elsewhere on the grounds, folks were admiring dwarf evergreens in the knot garden ("expresses the traditional elegance of garden design, which originated in Europe during the 16th century"), interrogating a fellow watering the Bonsai, motoring and cycling through forest and glade, picnicking in Rhododendron Valley, listening to a botanist assay the Cryptomeria japonica -- or just sitting quietly in a quiet place.

The aboretum, 444 acres of rolling hills and sloping lawns, shaded nooks and secret crannies in the middle of Northeast Washington, is something of a land for all seasons. With everything from research and education programs to pretty plants, it holds charms for gardener and sightseer alike.

It's a good time to commune with daylilies, lilies, waterlilies, crape myrtles and hibiscuses, plus such year-round attractions as the Gotelli Dwarf Conifer Collection, the Holly Walk, the National Bonsai Collection, the boxwoods, the National Herb Garden, half a dozen ponds and a 220-foot waterfall, which is still to be landscaped but began cascading a few weeks ago beside the Anacostia River. Alas, the ferns, especially broad-leaved evergreens, are still suffering from the bitter winter past; and everyone's in mourning for the camellias. "They haven't done too well," said aboretum staffer Elizabeth Ley, flashing a grin to go with her understatement.

Ley, standing before some stately Cryptomeria japonica beside the administration building, said they are also known as Japanese cedar.

"These are in the pine family, and closely related to redwood," she told a group of tree-lovers. "In Japan, where they account for one-third of the lumber supply, they're used to line the streets, and they grow up to 150 feet tall."

After nearly everyone moved on, Chester Shields, a retired trumpet player for the Marine Band, lingered for a tete a tete on Japanese cedar propagation. The best method, he learned, is to plant a branch-cutting and let it take root.

"Trees have been a hobby with me for the last 14 years," he said. "I like conifers, and I have a special love for trees that grow tall and slender." He gazed up at the cedars, and looked back pensively. "My favorites, though, are Chinese juniper and Italian cypress. They're the tallest and slenderest." NATIONAL ARBORETUM -- The main entrance is located at 24th & R streets NE; hours are 8 to 5 weekdays and 10 to 5 Saturday and Sunday, with the National Bonsai Collection open from 10 to 2:30 daily. You can go just for a stroll or benefit from expert advice. Among the aboretum's free events: on Tuesday, August 10, "Plant Propagation for Children" at 10:30; "The Falkland Islands: Plants, People and Penguins" at 1; and a "Bonsai Refinement Workshop" also at 1 (bring your own Bonsai; call 472-9279 for advance registration). For details on other doings, call 472-9100.