The brothers behind the painted flowers dotting yellow cabs throughout the city are not quite Christo and Jeanne-Claude. But since the public phase of their art initiative started 12 days ago, the two middle-age California natives, Ed and Bernie Massey, have seen their art project burgeon, with between 2,500 and 3,000 taxis being adorned with a painted flower skin.

Their nonprofit project, “Garden in Transit,” was conceived in 2000, with a goal of placing unique pieces of art on one of the most visible icons of New York: the yellow cab. About 27,000 vinyl sheets of flowers were painted by children in schools and hospitals, mostly in New York, beginning in 2006, with each meant to be affixed — temporarily — to taxis that requested some floral sprucing up.

The privately funded project is tied to the celebration of the 100th anniversary of the metered, motorized taxi in the city.

The Massey brothers — both tall, sandy haired, slim, relaxed, and gregarious — divide the project’s oversight between themselves, with Ed Massey, 43, heading up the artistic aspects of the project and Bernie Massey, 47, leading the educational side.

As the two stood in Union Square publicizing “Garden in Transit” to families and passersby yesterday, they spoke in cheerful tones about their work, pointing to pictures of bedridden children in hospitals smiling broadly as they painted flowers destined for the hoods of taxis.

“The flower is such a wonderful symbol of hope,” Ed Massey said. “We like to push themes that are common shapes for kids.”

While their work is hardly as high-profile as Christo and Jeanne-Claude’s “The Gates,” which attracted tens of thousands of visitors to Central Park in February 2005, the flowered taxis can seemingly be seen everywhere in Manhattan; the Masseys estimate the project has currently decorated about a fifth of the city’s 13,000 taxis.

“It’s a massive, massive undertaking and they have a lot of energy,” the commissioner of the city’s Taxi and Limousine Commission, Matthew Daus, said. “They’re going to need it — it’s one of the largest volunteer projects that we’ve seen.”

The scope of the initiative represents a high point for the Masseys: They say its location and visibility is far greater than their previous projects, which include applying children’s paintings to small airplanes, a tugboat, and portions of Chelsea Piers.

“In terms of impact, where you’re changing the biggest city in the country, nothing even comes close,” Bernie Massey said. “You can see it from 10 stories up.”

The bulk of the flowered sheets are placed on the hoods and trunks of cabs at a holding lot at John F. Kennedy International Airport, where the Masseys have assembled a few incentives to get the drivers to spend the seven minutes it takes for their volunteers to attach the adhesive vinyl sheets. The most tempting carrot “Garden in Transit” has to offer, they say, is a free one-time pass for the drivers to jump to the front of the airport’s lengthy taxi lines — as well as with some air fresheners and toy taxis.

The Masseys advocated for the project for years, and Mayor Bloomberg and the TLC finally signed on last year, even offering assistance in coordinating the initiative.

The project has created a new interest in the Masseys’ work, the brothers say, as calls and e-mail messages have been rolling in since the launch of “Garden in Transit.”

As for the future, Ed Massey said he has a few potential projects internationally, though over the long term, he is aiming for the stars: “There is a very real potential to unify community around a project that would culminate in space,” he said.