Purpletop Vervain

Description

Verbena bonariensis, 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 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. Verbena bonariensis is a tall and slender-stemmed perennial. It can grow to 6 ft (180 cm) tall and can spread to 3 ft (90 cm) wide. At maturity, it will develop a woody base. Fragrant lavender to rose-purple flowers are in tight clusters located on terminal and axillary stems, blooming from mid-summer until fall frost. The stem is square with very long internodes. Leaves are ovate to ovate-lanceolate with a toothed margin and grow up to 4 in (10 cm) long. Verbena bonariensis is a member of the South American vervains, which are polyploid and have more than 14 chromosomes. Among these, it is part of a lineage which might also include Verbena intermedia and seems well distant from Verbena litoralis or Verbena montevidensis for example. Sometimes, the name Verbena brasiliensis, Brazilian verbena or Brazilian vervain, is found for this species. However, this is the result of a mix-up with V. brasiliensis, the "true" Brazilian verbena, which has been erroneously referred to as V. bonariaensis by several botanists. Presently, the plant is on the invasive species watchlist for Washington state, naturalized in tropical and southern Africa, temperate Asia, Australia, New Zealand, the United States (including Hawaii), the West Indies, Macaronesia and the Mascarene Islands. According to Pacific Island Ecosystems at Risk, it is considered a weed in Fiji, New Guinea and other South Pacific islands.