Verbena hastata (American vervain, blue vervain or swamp verbena) is a flowering plant in the vervain family, Verbenaceae. It is a herb with opposite, simple leaves which have double-serrate margins, borne on stiffly erect, branching square stems. The purple flowers appear in summer. This is a common plant that occurs across North America. It is hardy and drought resistant.This species is a member of the diploid North American vervains which have 14 chromosomes altogether. Hybridization seems to ...