I love this plant because the foliage is just as pretty as the flowers! Last night the weather report was calling for possible frost so Jack put a large plastic barrel over this plant because it was so close to blooming. This morning the sun was hitting the barrel and probably the heat inside helped the blooms to open.
I think it's some sort of peony, but don't know for sure. It's another 'inherited' plant in our friendship garden. Isn't it pretty?