On other downtown rooftops, tall corkscrew-shaped turbines will bridle the winds that race across the plains. A new roof on Chicago's vast convention center will channel 55 million gallons of rainwater a year into Lake Michigan instead of overburdened storm drains.

Skeptics snickered 17 years ago when Mayor Richard M. Daley added flowers and trees to the city's honey-do list. They scoffed at the apparent folly of beautifying a sprawling, gritty urban landscape, figuring Daley for a modern-day Potemkin.

A few tulips, they figured, would be the end of it.

But the city-kid mayor raised on the rough-and-tumble South Side stuck with it. The greening project grew strong roots, giving Chicago a reputation as one of the nation's most committed environmental cities of any size. The company it keeps is not Newark and Detroit, but Portland and Seattle.

The urban environmental movement has spread from the margins to the mainstream, from a countercultural statement epitomized by the 1960s riff, "Save water; shower with a friend," to a policy option welcomed in boardrooms and council chambers. As other cities have climbed on board, Pacific Northwest progressives no longer have a corner on the market.

Since Daley began investing tax dollars in greening the city, Chicago has planted as many as 400,000 trees, according to city spokesmen. It employs more arborists than any city in the country. There are 2.5 million square feet of green roofs completed or under construction, boosted by expedited permitting and density bonuses for developers who embrace the concept.

"A lot of people think this is weird stuff, like yurts and straw bale houses. The mayor has set a big and important commitment. He really wants people to walk the talk," said Judith Webb, a U.S. Green Building Council spokeswoman. "When a city with a reputation and a population like Chicago begins doing green building as a matter of course, that's a real indication this isn't a fad or short-term trend."

On other fronts, the city provides 10,000 bike racks and announced a goal of quintupling bike lanes to 500 miles by 2015. The city spent $3.1 million on a bike station at Millennium Park that has 300 indoor bike spaces, along with lockers and showers.

Daley, who will decide soon whether to run for a sixth term, has taken some big hits this summer. The city council defied him and passed a minimum wage ordinance. A federal jury convicted his former patronage chief of rigging hiring to reward campaign workers. His beloved White Sox are nine games out of first place.

Amid the gloom, he was more than happy to talk about foliage.

"The more concrete we pour down America, the more deserts we destroy and farmland we destroy, the more global warming we're going to have," Daley said in an interview one recent afternoon. "If there's more trees, more flowers and more greenery, it helps the environment and attracts nature."

Daley is an especially big fan of green roofs. The City Hall roof, planted with more than 150 varieties of plants, is often 50 degrees cooler in summer than nearby asphalt roofs, whose temperatures can reach 170 degrees. It also houses beehives.

"The quality of the building outside affects how you live inside, what you're breathing," Daley said. "Anytime you fly into an airport, you see flat roofs. Imagine if every one of those flat roofs had a green roof. What a difference that would make!"

Daley, who won an award as a "design champion" last year from the Smithsonian's Cooper-Hewitt, National Design Museum, convinced Sadhu Johnston that his commitment is real. Famous for scouting ideas for Chicago while traveling, the mayor once toured a renovated Cleveland bank. Johnston was his guide.

Daley invited Johnston, who sees his life's work as greening American cities, to Chicago. The skeptical recruit, whose previous work was for nonprofits, came away inspired. He is now Chicago's 32-year-old environmental commissioner.

"It's about ecological designs," said Johnston, who bikes to work from Rogers Park on the city's north side. "It's about understanding how nature does its work and emulating it to do the work of cities. That involves looking at the environment as a resource and not an obstacle."

In practical terms, Johnston said it means using rainwater to irrigate gardens and flush toilets. It means harnessing sunlight and wind; workers even now are mapping the city's wind patterns. It means taking chances.

"Where we're experimenting," Johnston said, "not everything is going to be a clear success."

Earlier this year, the city issued $1 million in grants for solar thermal panels that generate hot water. Staffers focused on high-volume water users, including laundromats and health clubs. For the past year, the city has waived a service fee -- typically $5,000 to $50,000 -- for developers willing to install a green roof. The projects are assigned to reviewers empowered to expedite approval.

Michael Yannell intends to take advantage of initiatives for the "net zero energy use" house he is building in Ravenswood. If all goes well, the house will generate more energy than it needs. He expects a property tax break and a $5,000 grant for a rainwater collection system.

The city remains in its infancy as a eco-mecca, Yannell said, but he sees progress.

"I think Chicago is becoming a green city," said Yannell, a pharmacist who hired architects to design solar, wind and geothermal elements to his home. "Daley is a really big supporter, and, hopefully, we'll see more incentives offered in the future."

In the West Loop, once home to skid row and wholesalers of meat, fish and produce, the sidewalks are lined with cafes, sushi bars and nightclubs.

Owners say the changes on West Randolph Street began 10 years ago, when the city landscaped the medians and doled out money to rehab storefronts in advance of the 1996 Democratic National Convention. They noticed the city kept planting even after the delegates left town.

Despite 70 miles of planted medians, Chicago is hardly a new Eden. Among other challenges, the city of 3 million is clogged with commuter traffic, its sewage infrastructure is outdated, its beaches often close because of summertime bacteria and its recycling program has long been an inefficient tangle of missed opportunities.

"We're all humble about this," said Kathryn Tholin, chief executive of the Center for Neighborhood Technology, who had kind words for the embattled green mayor. "There's lot more to do, but if it's measured in commitment that goes all the way to the top in the city administration, we definitely have it."