Oxalis - A Cute Little Curse

Here in the Bay Area of California where I live almost anyone with a piece of dirt can tell you about oxalis, or wood sorrel, a cute shamrock-leaved little plant that grows and spreads with amazing speed. In fact, it's also called a shamrock, and the first time I saw it leprechauns and St. Patrick's Day did indeed spring to mind. The next several times I saw it, however, my mind turned to less kindly thoughts of eradication.

Some would charitably describe oxalis as a ground-cover. Most, including me, would probably call it a weed. Not long after it gets a foothold in your garden, you'll suddenly discover it's taken over. As Sunset's Western Garden Book puts it mildly, oxalis "Can be somewhat invasive in its favored woodland conditions." Actually, it appears to be invasive in plenty of other conditions: lawn conditions, garden conditions, that-damp-spot-under-the-hose conditions, and on and on.

There are quite a few varieties of oxalis, sporting yellow, light violet, or white flowers, all of which are very pretty to look at, but which rapidly lose their appeal as they appear by the hundreds in places where you were trying valiantly to grow something else. If you have an oxalis/wood sorrel/shamrock infestation, a great online resource, the Berkeley Parents Network has the following advice from their aptly-titled discussion "Oxalis - demon weed from hell." (No, you don't have to be a parent to use the site :-) It comes from Anthony Garza, Supervisor of Horticulture at the UC Botanical Garden in Berkeley - so he knows his stuff:

"Really, SPRAY [Roundup herbicide] and PULL and MULCH again and again if you wish to have anything resembling a landscaped yard that is under control. Organic controls would exclude the Roundup, and most have not had any long-term luck with those methods. You will have to concede with living with a certain level of infestation if you are not willing to use a glyphosate-based herbicide." Read Anthony's complete post.

Or if that's too much trouble, you could just decide to sit back and enjoy the invasion. There are certainly a lot uglier weeds than oxalis...here's a great illustration of one variety, Goat's Foot Wood Sorrel:


(Image courtesy of the US Department of Agriculture's National Agricultural Library)