It turns out that Warren’s flowers are indeed called buttercups, but not the same ones you may be used to seeing. Some comments from the previous post had me wondering. The scientific name is Oxalis pes-caprae, or the Bermuda Buttercup. It’s an oxalis flower, part of the wood sorrel family (clover-like leaves with 5-parted flowers).
Another common name for it is “Sour Grass.” Turns out it is somewhat edible, though in high quantities it can be toxic. That doesn’t stop the kids from chomping on the stems. They love the sour taste. You can often find kids at our Tuesday playgroup dining on handfuls of the stuff.
I found most of this information on the University of California Integrated Pest Management website and Wildflower Information.org. Great resources for someone like me who’s clueless when it comes to flower identification.