Verena bonariensis from Seed Savers Exchange
(Verbena bonariensis) (aka Purple Top) Introduced to England from South America around 1725. Stiff stems with dark green leaves support an endless succession of purple flowers up to and even after the first light frost. Thrives in warm dry soil, very easy to grow. Great for borders where height is needed. Tender perennial, usually grown as an annual, 3-4' tall.