Verbena bonariensis

Verbena bonariensis (purpletop vervain, clustertop vervain, Argentinian vervain, tall verbena, or pretty verbena) is a member of the verbena family cultivated as a flowering annual or herbaceous perennial plant. In USA horticulture, it is also known by the ambiguous names "purpletop" (also used for the grass Tridens flavus) and "South American vervain" (which can mean any of the numerous species in the genus Verbena occurring in that continent). For the misapplication "Brazilian verbena" see below.