A garden variety of the creeping buttercup, with double, yellow flowers with a green center. I don't have personal experience of growing this plant, the photo was taken in a private garden. According to the owner, it didn't spread much, but it can spread if the the soil is dense and moist, which are the ideal conditions for this plant. Considering that the species is a noxious weed, it might be surprising to learn that a number of garden cultivars are available in other countries. This is the only one I've encountered here.