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Conyza (horseweed, butterweed or fleabane) is a genus of flowering plants in the sunflower family.[4][5][6][7]

Conyza bonariensis.jpg
Conyza bonariensis
Scientific classification e
Kingdom: Plantae
Clade: Angiosperms
Clade: Eudicots
Clade: Asterids
Order: Asterales
Family: Asteraceae
Tribe: Astereae
Genus: Conyza
Less., 1832, conserved name not L. 1753 (syn of Inula) nor Hill 1756 (syn of Pulicaria) nor Lam. 1756 (syn of Psiadia in Rubiaceae)[1][2]

They are native to tropical and warm temperate regions throughout the world, and also north into cool temperate regions in North America and eastern Asia. The New World species of the genus are closely related to Erigeron (also known as fleabanes).[8]

The species are annual or perennial herbaceous plants, rarely shrubs, growing to 1–2 m tall. The stems are erect, branched, with alternate leaves. The flowers are produced in inflorescences, with several inflorescences loosely clustered on each stem.[8]

Many species of the genus Conyza are ruderal species and some have been found to be resistant to the herbicide glyphosate.[9]

Conyza bonariensis seed heads and flowers


  1. ^ Tropicos search for Conyza
  2. ^ Tropicos Conyza argentea Lam.
  3. ^ a b Flann, C (ed) 2009+ Global Compositae Checklist Archived 2014-11-15 at
  4. ^ Lessing, Christian Friedrich. 1832. Synopsis Generum Compositarum 203–204 in Latin
  5. ^ Tropicos, Conyza Less.
  6. ^ Cronquist, A. 1943. The separation of Erigeron from Conyza. Bull. Torrey Bot. Club 70: 629–632. 1943.
  7. ^ Nesom, G. L. 1990c. Further definition of Conyza (Asteraceae: Astereae). Phytologia 68: 229–233.
  8. ^ a b Flora of North America, Horseweed, Conyza Lessing
  9. ^ Zelaya, I. A.; Owen, M. D. K.; Vangessel, M. J. (2007), "Transfer of glyphosate resistance: evidence of hybridization in Conyza (Asteraceae)", American Journal of Botany, 94 (4): 660–73, doi:10.3732/ajb.94.4.660, PMID 21636434

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