For at least 15 years, I’ve been trying to get a decent photo of this flower which grows like a weed all around the edges of my garden. This morning, I came the closest to doing so so far. The flowers are from 1 to 1.5 inches (~2.5 to 4 cm) across and come with a warning. They are so invasive that it is illegal to plant them in some states in the U.S. Wish I’d known this before planting them. Thanks to Forgottenman for finally identifying them for me.