Lesser celandine. Formerly Ranunculus ficaria, now Ficaria verna. Cute but not native to USA. Can prove invasive and a nightmare and well-nigh ineradicable weed in gardens. Think VERY hard before introducing it to your garden.

Sigh. Well, that's pretty typical. We saw and purchased this house in very early spring, when it looked lush, but not much was identifiable. We've since discovered that 90% of what the previous owners planted is invasive. I thought this one would be okay, but I should have known better! Right now it's doing battle with mint, lamium, and ivy, so that's probably why it's not spreading more.

Thanks!