Verbena bonariensis

Verbena bonariensis, commonly known as the 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 United States 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 on the continent). For the misapplication "Brazilian verbena", see below.

It is native to tropical South America where it grows throughout most of the warm regions, from Colombia and Brazil to Argentina and Chile.