Oxalis — “sourgrass” — is the bane of many local gardens, but in Cesar Chavez Park, where weeds are kings, oxalis spreads a sweet blanket of sunshine across the verdant slopes at this time of year. Like several other weedy citizens of this park, oxalis pes-caprae, the local variety, is edible and may even be good for you in modest amounts, if you need a bit more vitamin C. The taste is a bit lemony and bitter. People may add the leaves and flowers to salads. Native American lore values the plant as a thirst quencher and possibly a cure for some common ailments. You could mash the leaves to make a kind of bitter lemonade, or you could make a tea. Or you could just enjoy it as a feast for the eyes in a park where you don’t feel compelled to dig it up, as you might in your garden, if you have one. Oxalis is a member of the wood sorrel family, which has about 800 members worldwide. It’s not a grass, as you can tell by looking at its leafy structure, somewhat reminiscent of (but unrelated to) clover. It’s a perennial. It’s tough to get rid of because it stores energy in its bulbous roots, which in some species (not here) grow large enough to be sold commercially like potatoes. It can spread rapidly because its seed pods, when mature, explode when disturbed and scatter seeds as far as twelve feet or more in all directions.