On an overcast Saturday morning, Christopher Nyerges — the head of Eagle Rock's School of Self-Reliance — gingerly skirts a feral clump of bright green weeds. "Always watch where you're stepping 'cause you might be stepping on our lunch," he says to the 17 students following him. Resembling troops in an outdoorsy New Age army, the group wanders through Pasadena's Hahamongna Watershed Park, scouring the dirt hills, shallow valleys and parched riverbeds of the land for edible plants as part of a wild food outing that Nyerges regularly teaches. Nyerges knows what most urbanites don't: that food is in the...