Tucked into a small lot next to a rundown walk-up apartment building at 40 S. School St., the office of Philip White Architects is easy to miss.

You could drive by it day after day without realizing it’s there, yet if you were to walk into the third-floor office, you would be surprised to find a peaceful oasis.

Two years ago the firm transformed a dilapidated building marked with graffiti into "green" offices, with a solar electric system, dual-flush toilets and sensor lights.

Today a small garden is growing on the office rooftop.

Two square plots on the plastic lumber deck are filled with drought-tolerant plants, including akulikuli, kupukupu ferns and succulents, which can withstand strong sun.

Along the border, there are modules of herbs, fruits and vegetables, including lettuce, cherry tomatoes, peppers, eggplants, rosemary, strawberries, basil and thyme, which come from FarmRoof, the latest venture by Alan Joaquin of the Wiki Garden. Philip White Architects’ rooftop garden is a demonstration project, according to associate Laura Ayers, just one of several sustainable concepts it shares with clients.

Besides cooling down the building, the garden provides a more aesthetic setting for lunch, and employees are welcome to take the harvest home.

The staff is experimenting with the plants and finding out which ones will grow or perish on the hot rooftop.

MOST PEOPLE think of gardens at ground level, forgetting they can grow up above, as well.

Scanning the Honolulu skyline, Joaquin says there is plenty of room for more rooftop gardens in this city.

There could potentially be rooftop gardens on offices stretching from downtown Honolulu to Waikiki, he said, and on top of supermarkets like Whole Foods Market. An estimated one-third of city rooftops could be set aside for gardens.

"There’s a lot of wasted roof space in Hawaii," he said.

A 2007 study by the University of Hawaii cited Kakaako, Waikiki and downtown Honolulu as three urban areas with rooftops that could potentially become gardens.

One-story big-box stores like Costco, Kmart and Home Depot also are good candidates for rooftop gardens.

From the sky the city would look like a patchwork of green. Environmental benefits include improved air quality and noise reduction. And instead of flowing into storm drains, rainwater runoff would flow back into the garden.

It would also take the meaning of "eating local" to a whole new level.

The California Academy of Sciences in San Francisco features a 197,000-square-foot rooftop garden — a living tapestry of native California plant species.

In dense urban cities like Chicago and New York, residents escape city life on rooftop gardens — even hold yoga classes up there.

Though small, White’s rooftop garden could well be the seed of a concept that will take root in Honolulu.

Nina Wu writes a column about environmental issues on the first Monday of every month. E-mail her at nwu@staradvertiser.com.