An herb garden filled with basil, peppermint and other tasty plants announced by signs that read "Touch me" is one of numerous year-round attractions at the 446-acre U.S. National Arboretum.

Another is the National Bonsai and Penjing Museum, composed of outdoor patios and greenhouse-inspired "pavilions" and open from 10 a.m. to 3:30 p.m. daily. Most people are familiar with bonsai, which look like tiny replicas of larger trees or shrubs and average about 18 inches in height. Penjing, on the other hand, does not produce leaves and resembles driftwood.

The mission of the federal facility, located only a few minutes from downtown Washington at 3501 New York Ave. NE, is to conduct research, provide education and conserve and display trees, shrubs, flowers and other plants to enhance the environment.

It is divided roughly into seven regions containing about 40 separate plant collections and gardens. The conifer collection lies along the northernmost border. Dogwoods are found at Dogwood Circle in the northeast corner.

With views of the Anacostia River, Hickey Hill Overlook on the eastern perimeter is surrounded by hollies, magnolias and the Chinese, Japanese and Korean collections. Underneath Hickey Hill is the Kingman Lake Overlook, next to the crabapple trees.

Beech Spring Pond and Gazebo is to the west. Fern Valley and the Native Plant Collections can be found along the southern border. Mount Hamilton Overlook, with its vista of the capitol, and the azalea gardens lie to the southwest.

As Linda Wilson, executive director of Friends of the National Arboretum, says, "Any time of the year is a good time" for a visit. In autumn, visitors go to see foliage. In winter, it's pine cones and holly, and in spring, tulips and daffodils.

But the spring and the summer support "more blooming plants, more floral displays," Wilson says. Summer highlights include day lilies, herbs, wildflowers and waterlilies on the Administration Building pond.

The arboretum's summer sights are within easy walking distance of each other. Stretched along the north and northwest borders, they also are close to one of the entrances, at 24th and R Streets NE. The arboretum is the only federally funded one in the United States. With acres of exotic and familiar flowers, plants and bushes and nine miles of paved roads, it also is one of the country's largest.

For example, Strybing Arboretum and Botanical Gardens in San Francisco's Golden Gate Park covers only 55 acres, and America's oldest arboretum, Harvard University's Arnold Arboretum in Boston, spans a mere 265.

Though Congress passed legislation in 1927 to establish a national arboretum, the site was not opened to the public until 1959 after its first major planting of about 70,000 Glenn Dale azaleas. The arboretum is administered by the U.S. Department of Agriculture's Agricultural Research Service, and its staff works closely with the National Capital Area Federation of Garden Clubs, Friends of the National Arboretum and the National Bonsai Foundation.

More colorful than its history are its flowers. Day lilies are dispersed over a sun-laden, five-acre plot east of the fence along Bladensburg Road.

The day lily collection includes more than 600 cultivars, a horticulturally or agriculturally derived variety of a plant. Gathering these flowers began in 1960 when the American Hemerocallis Society donated 150 day lily cultivars. "Hemerocallis," the botanical name for day lilies, is derived from Greek words meaning "beautiful day."

Volunteers do much of the gardening, says Mary Ann Jarvis, volunteer and events coordinator. The arboretum needs volunteers for at least one four-hour period weekly at the azalea gardens. Volunteers such as Hasty and Dery, who lead special programs, are needed for one three-hour session monthly. Those interested in volunteering should call Jarvis at 202-245-4565.

A 32-year worker at the arboretum, she says, "I feel very blessed that I have been allowed to come here and make people happy." She describes the arboretum as is "an oasis in our nation's capital" that "belongs to all of us."

Visitors seem to agree. In addition to the young folks giggling in the Herb Garden, grownups were biking along the 9.5 miles of paved roads, a twenty-something couple snuggled under a tree and senior citizens strolled among the day lilies. Other people come alone to enjoy a book in the peaceful shade of the Lee Azalea Garden. Many bring picnics. Beverages, but not food, are available in the gift shop. Some hikers make the half-hour trek to the Mount Hamilton Overlook.

"To the body and mind which have been cramped by noxious work or company," Ralph Waldo Emerson wrote, "nature is medicinal and restores their tone."

Volunteers and staff members at the arboretum likely would agree. "We are our nation's garden," Jarvis says. "We're a living museum."

-- Maura Kelly