butterweed. I like it because it has dark red-purple stems and I think that's cool. Unfortunately, they bloom at the same time as the redbuds and it clashes with the redbuds, which I find irritating, but which my youngest finds irrelevant. She told me to get over it.
It's also called Cress leaf groundsel and Yellowtop. For good reasons, as you can tell by the photos.
These flowers are all over out here this time of year. They're about 12-18 inches high and they bloom in the low spots and along the roadsides and banks. Clay doesn't bother them.
These leaves are basal - they are only at the base of the plant. They are also lobed, not heart shaped. That difference tells me that this is Packera glabella and not one of the other Packeras that look a lot like this.