The feathered bracts on the involucres finally helped me identify these pretty flowers as knapweed, genus Centaurea. I haven't been able to do any better than that yet. Some Centaurea species are invasive exotics while others are North American natives. These may be some escaped horticultural variety. Whatever they are, they are doing very well in a clearing near our house, and I think they are lovely.
- Connecticut Botanical Society's Knapweed selection
- USDA Plants Database entry for the genus Centaurea