Verbena hastata (Blue Vervain/Swamp Verbena)

From CONPS: Simpler’s-joy or blue verbena is a 2-5 ft., stout-stemmed perennial with numerous, pencil-like flower spikes branched upwards like the arms of a candelabra. Each flower spike has a ring of blue-purple flowers; the flowers at the bottom of the spike bloom first, and the ring of flowers appears to advance upward to the tips of the spike. This plant prefers wet environments; aka Swamp Verbena - plants adapt to disturbed wetlands or moist higher quality habitats. The larval host is common buckeye.