It is one of those eureka moments.

Jordan Pascua, a third-grader at Charles Barrett Elementary School in Alexandria, holds a tiny magnifying glass over a mint leaf cradled in his palm.

"I found an aphid," he says, with a great grin.

The setting is Barrett's one-year-old butterfly garden, which Barrett parents and teachers created as a cloister for exploration and calm discovery. Wispy bronze fennel, swamp milkweed and bee balm are some of the host plants here that will lure butterflies -- and hopefully spark some hands-on learning by the kids. The school serves kindergarten through fifth grade, and many of the students are apartment dwellers with limited access to the natural world.

"The garden's been a tremendous learning tool for us," says Cathy David, Barrett's principal until recently. "We're always looking for authentic learning."

Across the Washington area -- and the country -- there is mounting enthusiasm for using gardens, and the plants and vegetables they grow, to teach children about wildlife, food and the environment.

"It comes from the realization that if we don't make people who value the environment, things are going to go to pieces. You've got to start with the children," says Mary S. Rivkin, associate professor of early childhood education at the University of Maryland Baltimore County and author of The Great Outdoors: Restoring Children's Right to Play Outside.

Gardens, says Jim Flint, an education specialist at the National Gardening Association, "represent a whole range of opportunities for education -- discovery -- for kids of all ages. There's a sense, I think, of loss of connection to the earth that occurred with the material boom, the electronic boom, of the '80s and '90s. Many of the baby boomers who grew up with some feeling for the earth got lost along the way. As this generation now has children, they're remembering that something from their past is missing. There's a chance to re-create some of that by gardening with their children."

One of the largest garden facilities for kids lies in a spot that once belonged to George Washington. The rolling River Farm in Alexandria was maintained by the first president in the mid-1700s. Although he never lived there, Washington is thought to have planted the land then with wheat, rye and corn. Today, owned and run by the American Horticultural Society, it is planted into 10 highly imaginative "teaching gardens."

One is -- of course -- a butterfly garden. Another celebrates plantings that are playful and appeal to the very young. A third is somewhat wild, with species of grasses that allow children to feel as if they are in a giant nest. There are also an alphabet garden with plants for each letter; a bat cave; a tepee tree; a boat garden (with plants enclosing an actual small boat); a jelly bean garden (so named for its shape); and the Princess Diana memorial garden.

Not far from River Farm, and less elaborate, is the Fairfax County-run Green Spring Gardens Park. It, too, has a butterfly garden, as well as a fairy tale garden based on the Cinderella story, a water garden and a berry garden. The plots here are somewhat less interactive than the River Farm gardens. Green Spring provides school programs tailored to questions on Virginia's new Standards of Learning exams, to Boy Scout programs and, this summer, to preschoolers. According to assistant director Sherrie Chapman, the programs are designed to interest young people in gardening as a vocation: "Not everybody is suited to work behind a computer."

At Arlington's Barcroft Elementary School, the Leonardo garden is tied into art, specifically the school's curriculum-wide "Da Vinci Project." The garden brims with black-eyed Susans, joe-pye weed, New England asters, purple cornflowers and jack-in-the-pulpit, and art in the school's corridors echoes the colors and themes. "We use the garden for `teachable moments,' " says Barcroft Principal Miriam Hughey-Guy.

At Alexandria's Cora Kelly Magnet School, a kids' garden project is lush with growth: long grasses, clumps of day lilies, and lily pads covering a water-filled plot. Created four years ago, all of it has been planted by and is tended with the help of students. At its front sits a sky-blue ceramic tile etched with a poem written by a former student that embodies the ethos of the garden:

As I lay where the moss grows that's as green as a tropical sea,

I think about my feelings and nobody's there but me.

The garden has been designated a "schoolyard habitat" by the National Wildlife Federation. In all, 820 U.S. schools -- also including Barrett Elementary -- have sites so labeled.

There is a more traditional feel to the colonial garden at the Arlington Traditional School, which takes it cues from Colonial Williamsburg and is used by teachers when students study colonial Virginia. The garden features authentic plants of the era and similarly attentive historical details: a sundial fringed with lavender, a crushed oyster shell pathway, a colonial-style white picket fence. Not only is the garden used as a tie-in for trips to Williamsburg, but the Nature Conservancy, a nonprofit organization based in Ballston, uses the garden to teach kids about endangered plant species.

In Maryland, Brookside Gardens, renowned for its Japanese teahouse, ponds and acres of careful landscaping, offers children an interactive garden on the theme of a Native American folk tale called "The Three Sisters." It is planted with corn and beans and other crops and flowers that are associated with Native American culture. Several times a year, Brookside also offers "Discover Tables," which enable families and children to make nature-based crafts and take them home.

Every summer since 1971 the National Arboretum, a 440-acre swath of rare and colorful greenery abutting the Anacostia River, has provided a children's garden program. This summer more than 100 children are participating, each being given a 5-by-15-foot plot to create and tend. In addition to growing vegetables and flowers, the kids take part in skits and other activities that teach them about plants and the growing cycle.

All across the District, community garden plots spill out of unused patches of dirt along city streets. Teaching gardens, too, have begun to sprout, often in areas that can really use them.

"The kids named it God's Petworth Community Garden," says LeeAnn Schray, pastor for Lutheran Social Services for D.C., speaking of the cozy garden she has created for children and their parents out of an unused lot on Georgia Avenue. "It has been a parking lot and party spot at night. There were drugs and everything else going on back here. So, we leased the space. We wanted to do something wonderful for these kids."

Today, the lot is dotted with white plastic wading pools filled with dirt and planted with vegetables and flowers. Neighborhood kids helped Schray plant the garden and help her maintain it. Schray is talking to four neighborhood schools about building vegetable gardens on their grounds and then creating a habitat trail to join them all.

At Lincoln Multicultural Middle School in Columbia Heights, a joint effort with the Corcoran Gallery has produced a garden specializing in medicinal herbs, such as chamomile and mint. The idea is to give teenagers hands-on experience with plants that could lead some of them into a horticultural career, and, more generally, to encourage such character skills as patience and hard work. The students have also created a special peace garden, in memory of student Hang Nguyen, who was killed in 1996. Surrounding the garden beds are student-designed pillars, each decorated with colorful mosaic motifs.

At Watkins Elementary School in Southeast, local children's garden enthusiast Molly Dannenmaier helped parents and teachers create a dinosaur garden that is full of such antediluvian plants as mosses and ferns; a performing plants garden with Chinese-lantern and obedience plants and lady's mantle that, she says, "shines like jewels"; and a garden of time, with four-o'clocks and morning glories.

As Dannenmaier puts it in her book A Child's Garden, "In answer to children's inevitable curiosities about nature, we offer them books, television shows and computer learning programs instead of taking them outside to touch, feel and smell the real thing."

Barbara Hall is a freelance writer who frequently covers horticultural issues and education.