At One Bryant Park last summer, Richard Kohlbrecher, who is allergic to bee venom, first saw hundreds of honeybees darting in and out of the sprawling sedum ground cover on the green roofs he was inspecting. He turned his initial alarm into a housing plan for the secret tenants.

“I had never seen that before and it got me thinking: if there are that many bees in Midtown, maybe it makes sense to put up some hives,” said Mr. Kohlbrecher, vice president for operations for The Durst Organization, which owns the company’s 51-story-tower at 42nd Street and Sixth Avenue. The skyscraper houses the corporate and investment businesses of the Bank of America as well as Durst’s offices.

And so, unbeknown to the busy office workers and the tourists sunning themselves in Bryant Park, above them on the seventh-floor rooftop are now some 100,000 European honeybees brought in with two main hives earlier this summer.

Perhaps it’s not surprising that Durst has become a proponent of beekeeping. The company has green roofs on eight of its commercial buildings. One Bryant Park, which received a LEED platinum rating from the United States Green Building Council, houses the corporate and investment businesses of the Bank of America as well as Durst’s offices. Its “green” features include a special air-filtration system that filters out 95 percent of particulate matter, an urban garden room within the lobby, and the green roofs, which use compost made from waste from the building’s cafeteria.

And beekeeping has a long tradition in New York, now including such lofty perches as the terraces of the Waldorf-Astoria Hotel and the Whitney Museum of Art. Beehives are becoming increasingly common across the city, although there is no comprehensive list of their locations, said James Fischer, the director of education at TheHoneybeeConservancy.org, an advocacy group. This has accelerated in the last three years, since a ban on beekeeping instituted during the Giuliani administration was lifted.

It is costly to plant a lot of sedum and it can take a season or two before it naturally fills out; bees are an inexpensive way to hasten this process. But while a select number of private companies have begun employing them, “they don’t like to make their beehives public because of some people’s fears,” Mr. Fischer said.

Beekeeping has also been catching on atop buildings outside of New York. Earlier this summer, bee hives were added to the green roofs of the Minneapolis City Hall building, and similar environs have been encouraged in other urban areas with green roof habitats. In London, the number of urban beehives has exploded in recent years, to the point there was concern that the city had an insufficient supply of bee-friendly plants to feed the growing populations.

In New York, where bees have yet to face any food shortages, anyone can keep a beehive as long as it is registered with the city’s Department of Health and Mental Hygiene and there is a water source, something as simple as a bucket filled with water.

On the green roof at One Bryant Park, the bees’ natural pollination process helps maintain the area’s nearly 6,000 square feet, where the sedum was planted to help to reduce urban heat energy and runoff.

“Putting honeybees in a location supercharges the normal pollination process,” said Chase Emmons, a managing partner and the apiary director at Brooklyn Grange. The company, with locations in Long Island City and the Brooklyn Navy Yard, sold the Durst Organization its two beehives in June and is helping the company maintain them and harvest the honey.

The honeybees are a Russian variety, known for their hardiness and ability to survive cold Northeastern winters. That could come in handy because bees have been plagued in recent years by colony collapse disorder, a mysterious malady that has wiped out as much as 50 percent of the country’s commercial beehives in the last year alone.