Verbena bonariensis

This is about the Verbena bonariensis described by Linnaeus. See also below for a common misapplication of this taxon.

Verbena bonariensis
Scientific classification
Kingdom:	Plantae
(unranked):	Angiosperms
(unranked):	Eudicots
(unranked):	Asterids
Order:	Lamiales
Family:	Verbenaceae
Genus:	Verbena
Species:	V. bonariensis
Binomial name
Verbena bonariensis L.
Synonyms
Verbena patagonica

Verbena bonariensis (Purpletop Vervain, Tall Verbena, Clustertop Vervain, or Pretty Verbena) is a member of the verbena family (Verbenaceae) cultivated as a garden annual or perennial. In 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 supposed common name "Brazilian Verbena" or "Brazilian Vervain", 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.

Description

Verbena bonariensis, Purpletop Vervain, is a tall and slender-stemmed perennial. It can grow to 6 ft (120 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.

Taxonomy and systematics

Its specific epithet refers to Buenos Aires.^[1]

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.^[2]

Sometimes, the common name "Verbena brasiliensis, 'Brazilian Verbena' or 'Brazilian Vervain, is found for this species^[3]. 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^[4].

Subspecies

There are two named subspecies:^{[5][citation needed]}

• Verbena bonariensis ssp. bonariensis L.
• Verbena bonariensis ssp. conglomerata Briq.

Cultivation

Closeup of Verbena bonariensis flower.

Verbena bonariensis, the tall, slender-stemmed Purpletop Vervain, is often cultivated by the plant nursery trade as an ornamental plant for traditional and drought tolerant and 'pollinator-host' gardens and public landscapes and parks.

It is a tender perennial hardy in USDA Zones 7-11. It can be grown as an annual in areas where it is not winter hardy and will bloom in the first year when grown from seed. Its long internodes give it a sparse appearance but allow it to intermingle and coexist with other plants. The flowers are very attractive to butterflies, and provide nectar for native bees and many beneficial garden insects.

This species grows best in a well-drained soil. It prefers full sun to partial shade and needs regular moisture. It has a reputation of being rarely attacked by insect pests, but may be susceptible to powdery mildew. V. bonariensis is commonly grown from seed which germinate readily without pre-treatment, but also can be propagated from herbaceous stem cuttings.

Verbena bonariensis is reportedly used as a veterinary abortifacient in Australia, although details are lacking.

Invasive species

V. bonariensis self-seeds readily. This ability has raised concerns that it may become an invasive species and noxious weed in favorable habitats. It has naturalized in a number of southern U.S. states.

Presently, the plant is on the invasive species watchlist for Washington State,^[6] naturalized in tropical and southern Africa, temperate Asia, Australia, New Zealand, the United States (including Hawaiʻi), 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.^[7]

Footnotes

1. ^ CalFlora Botanical Names
2. ^ Yuan & Olmstead (2008)
3. ^ E.g. USDA (2007)
4. ^ UDSA (2008a)
5. ^ ITIS [2000]
6. ^ WSNWCB (2007)
7. ^ Pacific Island Ecosystems at Risk: V. bonariensis

References

• Bailey, L.H. (1951): Verbena bonariensis. In: Manual of Cultivated Plants: 840. Macmillan Publishing Company.
• Integrated Taxonomic Information System (ITIS) [2000]: Integrated Taxonomic Information System Verbena bonariensis (TSN TSN 32128). Retrieved 2008-AUG-07.
• United States Department of Agriculture (USDA) (2007): Germplasm Resources Information Network - Verbena bonariensis. Version of 2007-JAN-21. Retrieved 2008-AUG-07.
• United States Department of Agriculture (USDA) (2008a): Germplasm Resources Information Network - Verbena brasiliensis. Version of 2008-FEB-07. Retrieved 2008-AUG-07.
• United States Department of Agriculture (USDA) [2008b]: USDA Plants Profile: Verbena bonariensis. Retrieved 2008-AUG-07.
• Washington State Noxious Weed Control Board (WSNWCB) (2007): Tall Verbena, Purple Top, Cluster Flower Vervain. Version of 2007-MAR-31. Retrieved 2008-AUG-07.
• Yuan, Yao-Wu & Olmstead, Richard G. (2008): A species-level phylogenetic study of the Verbena complex (Verbenaceae) indicates two independent intergeneric chloroplast transfers. Mol. Phylogenet. Evol. 48(1): 23-33. doi:10.1016/j.ympev.2008.04.004 (HTML abstract)

External links

• Missouri Botanical Garden Kemper Center for Home Gardening - Verbena bonariensis (Purpletop)
• GRIN-Dr. Duke's Phytochemical and Ethnobotanical Database
• Dave’s Garden: Verbena bonariensis
• Pacific Island Ecosystems at Risk