Blue Vervain is a tall, sun-loving, clump-forming wildflower with a long bloom time, from July through September. 
 
     Its tiny-yet-dashing purple flowers bloom from the bottom up on stiff stalks.  It grows naturally in moist meadows and thickets and along the edges of ponds and rivers.
 
     Blue Vervain has some salt resistance and feeds butterflies, moths, wasps and native bees.  Cardinals and other birds eat the seeds. 
 
     Verbena is sometimes short-lived but readily self seeds.  It typically forms colonies by slow-spreading rhizomes.  It is not aggressive, though, and rarely outcompetes other plants.  
 
     Maybe think of Blue Vervain as a companion plant, rather than a stand-alone.  Try mixing it with other meadow plants, like Foxglove, Goldenrod, Asters, Ironweed.