But the crew was undeterred, and by the wee hours, they had transformed the blight into bloom with green bushes and an array of colorful flowers.
City workers on overtime? Nope, no budget for that. These were "guerrilla gardeners," a global movement of the grass-roots variety where people seek to beautify empty or overgrown public space, usually under the cover of darkness and without the permission of municipal officials.
"What we're fighting is neglect," said guerrilla gardening guru Richard Reynolds of London, founder of the Web site guerillagardening.org.
Getting approval to beautify public property can be cumbersome, so guerrilla gardeners in cities worldwide take matters into their own dirt-caked hands.
"We try not to let bureaucracy stand in the way," said accountant Steven Coker, who maintains an unsanctioned garden across from his house near an exit of the Santa Monica Freeway in West Los Angeles.
After starting his garden about 12 years ago, Coker has tried several times to officially take over its upkeep but to no avail.
Los Angeles Councilman Tom LaBonge said he supports guerrilla gardening as long as people don't present a safety hazard or impede traffic.
"I'm a guerrilla gardener, but I'm mostly just a maintenance guy," LaBonge said. "I pull weeds when I'm out walking. Everyone is welcome to do it. The city needs help."
Scott Bunnell, who has maintained a guerrilla garden on a median in Long Beach for about 10 years, said he wants to demonstrate that low-maintenance gardens are possible in Southern California's arid climate.
"Maybe I can help (show) municipalities, cities and whatnot by using dry, tolerant plants ... that they could make good use of the landscape," he said.
Reynolds said the modern form of guerrilla gardening started in the 1970s in New York, where the movement has reached its ultimate goal -- gardens planted without permission are now maintained by the city's parks and recreation department. He said Montreal is close to sprouting some synergy with guerrilla gardeners.
But most cities, including London and Los Angeles, aren't quite there yet, and so the 27-year-old music and drama teacher who organized the Hollywood Freeway offramp project is intent on staying covert and anonymous -- even requiring that his crew use aliases such as his own, "Mr. Stamen," or "Phil O'Dendron."
"If authorities come by, there's no leader," he yelled as his fellow gardeners dispersed over the median. "Nobody knows anybody."
As the gardeners weeded and picked up trash -- including a green sleeping bag and some underwear -- a few police cruisers drove by, but none stopped.
Gardening on public land without a permit is against the Los Angeles city code, said Cora Jackson-Fossett, a spokeswoman for the Department of Public Works.
Violators can be fined and go to jail, she noted.
"It's just in a city of this size, and in any municipality you have, there's rules and regulations, and we need everyone to follow them," Jackson-Fossett said.
Still, many who guerrilla garden in Los Angeles and elsewhere said they have never faced any serious legal threats. Often times, police or other city workers will stop and ask what the gardeners are doing then move on when they hear the innocent answer, "I'm gardening."
Most guerrilla gardeners don't go to the same lengths as Mr. Stamen to stay anonymous. Some, like Reynolds and Bunnell, have even moved into the sunlight with their work.
Bunnell said he gardens mostly in the early morning hours on his way to work in order to maintain a low profile.
But after getting positive feedback from residents in the area and encouragement from a city official, Bunnell decided to approach the city about a larger garden he has in mind -- one that would beautify as well as prevent erosion.
"I've been wanting to do this project for a long time," he said of the mile-long site on a bluff in Long Beach. "I'm hoping that they will just let me do a little area of it just to see how it would work out."
It also seems Bunnell's attempted collaboration with city officials is becoming less of an exception in the guerrilla gardening world.
James Caviola, an attorney who lives in Seal Beach, started guerrilla gardening about 12 years ago with just one tree in front of his house.
"My goal was to beautify the neighborhood," he said.
Caviola said he eventually raised money to help elect tree-friendly council members, and he's now working with the city to put trees on street medians and sidewalk parkways.
He does the work for free with the help of the corporation he created, Trees for Seal Beach.
Caviola said his sanctioned, out-in-the-open gardening no longer qualifies him for guerrilla status -- unlike Mr. Stamen, who didn't finish his work on that Saturday night until after 2 a.m.
Mr. Stamen and his guerrilla group have filled about a third of the median with succulents such as grass-like flax, aloe and red, blue, pink and yellow kalanchoes -- all donated by members of the group. They plan to finish landscaping the rest of the patch soon.
A sign sticks up from the dirt at the edge of the median closest to Sunset Boulevard.
"Guerrilla Gardening," it reads. "Please water me."