This plant came in a packet of mixed bee-friendly seeds. I can't find it in my wildflower guides, which suggests it isn't a native (but could also mean I'm crap at looking things up.)
There are five purplish petals on each flower, with quite long stamens, and they come in clusters. The stems are round with short hairs, but not very hairy. The leaves are lobed and arranged alternately on either side of the stem. And the bumble bees do seem to quite like it. It's around a foot tall (haven't actually had the tape measure out.)