- Conyza canadensis
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Conyza canadensis 
Scientific classification Kingdom: Plantae (unranked): Angiosperms (unranked): Eudicots (unranked): Asterids Order: Asterales Family: Asteraceae Tribe: Astereae Genus: Conyza Species: C. canadensis Binomial name Conyza canadensis
(L.) CronquistConyza canadensis (formerly Erigeron canadensis L.) is an annual plant native throughout most of North America and Central America. Common names include Horseweed, Canadian Horseweed, Canadian Fleabane, Coltstail, Marestail and Butterweed.
It is an annual plant growing to 1.5 m tall, with sparsely hairy stems. The leaves are slender, 2–10 cm long and up to 1 cm broad, with a coarsely toothed margin. The flowers are produced in dense inflorescences 1 cm in diameter, with a ring of white or pale purple ray florets and a centre of yellow disc florets.
Horseweed is commonly considered a weed, and in Ohio it has been declared a noxious weed.[1] It can be found in fields, meadows, and gardens throughout its native range. Horseweed infestations have reduced soybean yields by as much as 83%. It is an especially problematic weed in no-till agriculture, as it is often resistant to glyphosate and other herbicides. Farmers are advised to include 2,4-D or dicamba in a burndown application prior to planting to control horseweed.
Horseweed is much the most common of the alien Conyza species in Britain, and is found from northern Scotland to Cornwall. It is the only one of the British Conyza species that grows as a weed of arable land: the others are casuals of waste and disturbed ground in towns and by roads and railways. It is not invasive of any natural or semi-natural habitats.
C. canadensis can easily be confused with C. sumatrensis, which may grow to a height of 2 m, and the more hairy C. bonariensis which does not exceed 1 m. C. canadensis is distinguished by bracts that have a brownish inner surface and no red dot at the tip, and are almost free of the hairs found on the bracts of the other species.[2]
References
- ^ Germplasm Resources Information Network: Conyza canadensis
- ^ Conyza sumatrensis, International Environmental Weed Foundation
- A. Davis, K. Renner, C. Sprague, L. Dyer, D. Mutch (2005). Integrated Weed Management. MSU.
- Everitt, J.H.; Lonard, R.L., Little, C.R. (2007). Weeds in South Texas and Northern Mexico. Lubbock: Texas Tech University Press. ISBN 0-89672-614-2
External links
- Conyza canadensis, ITIS Report
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