"The more crowded a city is, the more new ideas come squeezing out of the ferment in a combination of need and opportunity," said Peter Harnik, director of the Center for City Park Excellence at the Trust for Public Land.
In the last two years, San Francisco - 17,505 people per square mile, compared with Los Angeles' 8,087 - has had a proliferation of tiny parks carved out along sidewalks and streets. They have become progressively smaller: from plazas and promenades to parklets and now parkmobiles.
When parking spots began turning into parkland, retailers and drivers groused: "So where do we put the cars?" Those who advocate for more green space in the city worried the miniatures would replace traditional parks. Even former Mayor Willie L. Brown Jr. got into the fray, deriding "overgrown flower boxes" that he said were a magnet for the homeless.
"The first one I came across had obviously been used as a bathroom," Brown carped. "The second one I visited, a guy and gal were 'socializing' in the bushes."
But proponents argue that even the tiniest of green spaces bring a little nature into miles of otherwise unfriendly concrete, particularly in a city where only a fraction of the downtown is open space and 70 percent of the streets are dedicated to private vehicles.
So what do San Franciscans, those pavement pounders who actually have a parkmobile in their own patch of the public realm, think of the beautification effort? It depends entirely on the day.
One recent Tuesday morning, an urban refuge beckoned those navigating the gritty sidewalk beneath gray skies. It was bright, perky, hard to miss. The meter beside it flashed "expired." Its long bench and discreet sign proffered a welcome: "All seating is open to the public."
Trucks and buses rumbled by. Sirens wailed. Pedestrians shot the custom Dumpster curious looks. Thirty minutes passed, then 60, then 90. No one sat down.
A heavyset, elderly man with a cane eyed the little refuge and hobbled on by. A panhandler clutching a white trash bag turned his back on it as he asked passersby for a quarter, "for my laundry. I'm telling you the truth!"
"Sort of ridiculous" was San Francisco native Jerry Adams' assessment as he ambled past the parkmobile, with its hard, narrow inset bench (the better to deter sleepers) and arbutus trees. "You can't just go plunking them down anywhere."
Wednesday was a completely different story.
The parkmobile had been rolled a bit south to a weekly lunchtime collection of food trucks called Off the Grid.
By the time the sun had burned off the fog, the folding tables had filled, and local funk band Bohemian Knuckleboogie had launched into a particularly soulful version of "Days of Wine and Roses," the parkmobile was becoming an integral part of the South of Market Street scene.
Victoria Jeffries whipped her iPhone out of her purse and focused it on the bright red Dumpster. She'd just devoured garlic noodles and a five-spice pork skewer when she came upon San Francisco's newest green space.
A lawyer with the Federal Trade Commission in Washington, Jeffries said her "backyard" was the National Mall. The micropark "managed to pack such joy into such a small, little parcel. . . . I thought it was quirky and interesting and worth a photograph."
Elsa Kim wasn't so sure. The 25-year-old project manager for a high-tech start-up plunked down on the bench, stretched her legs, and methodically made her way through a salted caramel cupcake.
On the plus side, she said, the parkmobile can be moved around to follow the sun, a scarce commodity in this foggy city. On the minus side? It can be moved around, dragged by a little gasoline-powered tractor, which makes her wonder: "I'm not sure I feel like it's the most green of parks."
The movable fleet, which eventually will number six, was commissioned by the Yerba Buena Community Benefit District. Each costs about $6,000 and will spend a couple of months in place before being moved to other sites.