Found in southwest Ohio, blooming in late May, mixed forest, limestone slopes, clay soil. About 1.5 to 3 ft. tall. Sorry for the poor photos - I took quick snapshots thinking that's all my wife would need to immediately I.D. it. She doesn't know and we couldn't successfully key it out. Blossoms are light lavender-pink, similar to the paler variations of Phlox divaricata. Thank you!
Hi, Iodanthus pinnatifidus : Online Virtual Flora of Wisconsin - Iodanthus pinnatifidus Very cool! Iodanthus - Wikipedia