Every winter after the rain, oxalis starts popping up. Maybe even during the rain; I don’t know for sure. But one thing is certain: On that day when you glance up on a walk and think, “oh, it’s green again,” part of the reason for the change in color is oxalis.
Bane of gardeners, this aggressive weed grows in yards, between sidewalk cracks, on hillsides, in planter boxes. The oxalis we all hate is Oxalis pes-caprae, a native of South Africa. (Which also gave us ice plant. Thanks a lot, South Africa.)
Oxalis is just about impossible to get rid of. Our La Lenguan neighbors have it, too. Actually, it’s all over the city. I’ve never had any luck eradicating it. I’ve heard that what you really have to do is dig down and remove every single god-forsaken bulb. One of these letters to the Chronicle from 2007 suggests getting chickens. So there’s that option.
It’s also known as sourgrass–and also, apparently, as Bermuda buttercup (though I don’t think I’ve ever heard that one before). In small quantities it’s even edible. You can chew the flower stalk or eat the leaves; it’s kinda peppery-lemony, like a woodsy lemon drop.
Oxalis afficianados will point out that not all oxalis are bad. In fact, we even have some nice native ones, including redwood sorrel (Oxalis oregana), which grows in redwood forests. But the oxalis known as oxalis is a serious pain. To part on a really cranky note, this essay by science writer David Quammen explains much more eloquently than I ever could why most weeds suck.