Verbena bonariensis

About

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 and South American vervain. For the misapplication "Brazilian verbena", see below.

Summary from Wikipedia