What plant is that?

This lovely native wildflower will appear soon in our damp meadows, fields and shorelines. In Newcomb’s this month’s Mystery Plant is a wildflower reaching 2 to 8 feet in height with flowers of 7 or more regular parts (yellow disk flowers and blue or purple ray flowers; this group has its own section of the book and note the name change on GoBotany!) and alternating leaves that are lance shaped with a heart-shaped leaf base that clasps the stout, bristly-hairy stem. Each flower head is 1-2 inches wide with 40 to 50 violet-to-purple ray flowers (rarely rose colored or even white).