Rocheblave Street, in New Orleans's Broadmoor district, resounds with the squabbling of wild parakeets and the whine of power tools. It's a Monday morning in late April in this recovering 2,400-home neighborhood, initially marked for demolition by the mayor's rebuilding commission. The breeze is thick with the smell of fresh paint. The street is nearly shadowless, the Louisiana sun unbroken. This pronounced absence, open sky where the crowns of trees formerly reigned, is the reason arboricultural philanthropist Monique Pilié is down on hands and knees, preparing a hole for a lissome Japanese magnolia sapling, which sits in a pot nearby. With two volunteers from a team of 15 or so, she combs the black Delta soil clean of roofing tiles (deposited 32 months ago by Hurricane Katrina), then plants the tree in their stead. It's roughly the 1,900th Pilié has put in the ground since the floodwaters subsided.

"We lost 70 percent of our tree canopy in the storm," she says. "Well over 100,000 trees. I wanted to do something. I wanted to give back to my city."

So she headed for high ground. A few months after the storm, in the winter of 2005, Pilié sold her house, quit her job, and began her Hike for KaTreeNa, a fundraising trek up the Appalachian Trail. Her plan was to return home and plant a tree for each mile that had passed under her boots: 2,175 of them. All told, Pilié has raised more than $100,000, and since October 2006, when she crossed the AT's finish line and descended Maine's Mount Katahdin, she's been a storm herself, of sweat, dirt, and shovels. Every week, across the Crescent City, she plants 50 to 60 trees—live oak, magnolia, and cypress saplings. All you need is a front yard. If her green thumb doesn't blow out first, Pilié expects to hit her goal this fall, three or so years ahead of schedule. Then, well … "I guess I'll have to go back and walk the trail backwards."

If people like Pilié keep at it, New Orleans's new reputation as the nation's capital of grassroots initiative and vigilante dogooderism may soon eclipse its renown for crime, poverty, and ill-considered toplessness. Nearly three years after the levees broke, it's not the governments of Louisiana and the United States but the citizens, the volunteers still pouring in by the thousands every season, and a host of pathbreaking nonprofits that are re-creating New Orleans and, in the process, striving to make it a model 21st-century American city.

Crooner Harry Connick Jr. and saxophonist Branford Marsalis, both natives, dreamed up the soon-to-be-completed Musicians' Village, a 72-home, Habitat for Humanity–built community in the famously ravaged Lower Ninth Ward. It promises to bring many displaced jazz and blues artists back to this too-quiet town. "We wanted to do what we could to facilitate the continuation of traditional music in New Orleans," Connick says. "I'd worked building houses with Habitat before Katrina, and after the storm the Musicians' Village was a perfect opportunity to help get musicians into their own homes—some of them for the first time in their lives—and to do something for the city in a way that was close to my heart."

Before the sandbags were even dry, L.A.-based eco-stewards Global Green moved in and began a number of ambitious projects. In collaboration with actor Brad Pitt (who's since spun off with his Make It Right Foundation, a volunteer-and-donation-based initiative aimed at building hurricane-proof homes designed by leading architects), GG "adopted" the Holy Cross neighborhood in the Lower Ninth, where it's undertaken a green housing development that would make Al Gore fall to his knees in ecstasy. Just this March, they completed the first house in the city to attain a LEED Platinum designation, a futuro shotgun with enough eco-gadgetry to render it carbon neutral and use zero net energy. Other projects include community education and grants for the greening of schools.

Speaking of New Orleans's schools, heretofore among the most neglected in the nation: Uptown on Valence Street, at the Samuel J. Green Charter School—a blighted junior high before the storm—teacher Donna Cavato has paired with Alice Waters, of Berkeley's Chez Panisse, to build a Louisiana version of the celebrity chef's Edible Schoolyard program, a student-managed garden workshop. Here, inner-city kids (98 percent of whom live below the poverty line) learn organic agriculture, nutrition, seasonal foodways, and composting. A scant year and a half after breaking ground in the fall of 2006, ESY NOLA transformed a school that "looked like a prison," as Cavato puts it, into an urban oasis. Five days a week, kindergarteners to eighth-graders gather for lessons under an airy pavilion and then, armed with trowels, mulch, and seeds, roll up their sleeves and go to work tending a cornucopia of native crops—tomatoes, okra, satsuma trees, etc.—where once lay an expanse of cracked concrete.

Here on Rocheblave Street, Pilié plants the last tree of the day, a leggy crape myrtle with pale green leaves. She heaps the dirt in a wide ring around the trunk to capture and retain moisture. "A levee," she says.

"The good kind," says a volunteer, dusting dark earth from her hands.

Then Pilié climbs into her pickup and rolls a few blocks over, to a construction site on South Tonti Street. Under the mild spring sun, with the help of Home & Garden TV and nonprofit carpentry corps Rebuilding Together, a crew of paint-stained volunteers is welcoming a family of nine back into a house they left under seven feet of water.

Pilié chats with Hal Roark, a resident who's been helping oversee the Broadmoor district's revival. "They were going to bulldoze this place, all these homes," says Roark. "We said, ‘Screw you. We'll bring it back ourselves.' " He gazes with pride at the porch roof, where a volunteer, brush in hand, is slathering an optimistic shade of sky blue on a gable. "Almost three years later, we're not waiting for the government," Roark says. "When the government fails, this is the kind of thing you have to do. You have to be the cavalry you want to see coming over the hill."