I was SO hoping this would be a buttercup. Not only does the family flower name Ranunculus sound like something out of a Harry Potter Herbology class, but I’m fond of the character in Gilbert & Sullivan’s HMS Pinafore.
In fact, I am pretty sure this is not a buttercup but is, instead, a Silver Cinquefoil (Potentilla argentea). I could be wrong about that too. I need to verify that this yellow flower has silver on the underside of its leaves – hence the flower name – but it certainly looks like the other pictures I’ve seen of it. In particular, unlike the buttercups or the sorrels or any rose-like yellow flower with 5 petals, there are distinct gaps between the petals.