“What makes a Marin County coyote look over the Golden Gate Bridge and say, ‘I’m going over there’?” wondered landscape architect Marcel Wilson, gazing over his backyard garden at the San Francisco Bay and hazy hills beyond. “The pressure to have your own territory.” Coyotes colonize empty parks in the city, but homebound humans are less lucky: A patch of green is hard to come by here, where houses like Wilson’s 1929 Spanish-revival number are built in block-long units and set into hills sliced by tunnels and roads. Meanwhile, the rugged peninsula’s once freewheeling streams have been stuffed into a subterranean ghetto of pipes and storm drains. So when Wilson found a relatively untamed spring bubbling up in a corner of this 1,250-square-foot yard, he bought the house and planned a garden, carving out his own territory on a small scale.

The first step was freeing the stream, which now cascades through copper runnels from under the deck to an iris-studded wetland. The rest grew around it: a raised lawn (built with dirt excavated from the building where Wilson’s wife’s jewelry-making studio is now located), the weathered boardwalk (its decking and steel salvaged when Wilson renovated the house), and a pad of rounded stones planted with native maples. Though its flora is packed tightly within the garden, its edges bleed. A neighbor’s Japanese maple pokes through holes in the fence; a swing-out window frames Mount Diablo in the distance; a hidden door allows lemon-picking excursions to the next yard over. Visitors—red-tailed hawks, newts, skunks, and a particularly rambunctious raccoon—enter freely. Like Wilson, they are drawn to the spring, a source of water that sustains multitudes. “It’s our Mississippi,” he says.