Looks like perennial geranium, G. Sanguineum.

Yes that's it! Thank you so much.

I pulled all mine several years ago--and am still pulling seedlings. They throw their seed, come up everywhere and are not easy to pull out even when small.

I like mine and don't find the seedlings problematic... But I am a pretty messy gardener.

Forgot to say: I often shear mine after it's done blooming, since the foliage starts to look ratty, and that stops it from seeding itself. The new foliage grows back into a mound.

Jayco: that's a good tip, and the kind of thing that I often forget to do!