Erigeron canadensis

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Erigeron canadensis
Conyza-canadensis-plant.jpg
photo taken in Netherlands in 1984
Scientific classification
Kingdom: Plantae
(unranked): Angiosperms
(unranked): Eudicots
(unranked): Asterids
Order: Asterales
Family: Asteraceae
Tribe: Astereae
Genus: Erigeron
Species: E. canadensis
Binomial name
Erigeron canadensis
(L.) Cronquist[1]
Synonyms[1]
Canadian fleabane (Erigeron canadensis) essential oil in a clear glass vial

Erigeron canadensis (synonym Conyza canadensis) is an annual plant native throughout most of North America and Central America. It is also widely naturalized in Eurasia and Australia.[2] Common names include horseweed, Canadian horseweed, Canadian fleabane, coltstail, marestail and butterweed. It was the first weed to have developed glyphosate resistance, reported in 2001 from Delaware.

Description[edit]

Erigeron canadensis is an annual plant growing to 1.5 m (60 inches) tall, with sparsely hairy stems. The leaves are unstalked, slender, 2–10 cm long and up to 1 cm (0.4 inches) across, with a coarsely toothed margin. They grow in an alternate spiral up the stem and the lower ones wither early. The flowers are produced in dense inflorescences 1 cm in diameter. Each individual flower has a ring of white or pale purple ray florets and a centre of yellow disc florets. The fruit is a cypsela tipped with dirty white down. [3]

Erigeron canadensis can easily be confused with Conyza sumatrensis, which may grow to a height of 2 m, and the more hairy Erigeron bonariensis which does not exceed 1 m (40 inches). Erigeron canadensis is distinguished by bracts that have a brownish inner surface and no red dot at the tip, and are free (or nearly free) of the hairs found on the bracts of the other species.[4][5][6]

Distribution and habitat[edit]

Horseweed originated in North America and is very widespread there,[2] but has spread to inhabited areas of most of the temperate zone of Asia,[7] Europe,[3][8] and Australia.[9] It is found in Britain from northern Scotland to Cornwall growing as a weed of arable land. It is not invasive of any natural or semi-natural habitats.[citation needed]

Weed status[edit]

Horseweed is commonly considered a weed, and in Ohio it has been declared a noxious weed.[10] It can be found in fields, meadows, and gardens throughout its native range. Horseweed infestations have reduced soybean yields by as much as 83%.[citation needed] It is an especially problematic weed in no-till agriculture, as it is often resistant to glyphosate[11] and other herbicides.[12] Farmers are advised to include 2,4-D or dicamba in a burndown application prior to planting to control horseweed.[citation needed]

Uses[edit]

The Zuni people insert the crushed flowers of E. canadensis var. canadensis into the nostrils to cause sneezing, relieving rhinitis.[13] A tincture can be made from the dried flowering tops of the plants.

Horseweed is a preferable material for use in the hand drill method of making friction fire.[3]

References[edit]

  1. ^ a b The Plant List, Erigeron canadensis L.
  2. ^ a b Biota of North America Program, 2014 county distribution map, Erigeron canadensis
  3. ^ a b c "Canadian Fleabane: Conyza canadensis". NatureGate. Retrieved 2013-12-31. 
  4. ^ Conyza sumatrensis, International Environmental Weed Foundation
  5. ^ Green, Deane. "Horseweed, Marestail". Retrieved 2014-08-09. 
  6. ^ Flora of North America, Conyza canadensis (Linnaeus) Cronquist, Bull. Torrey Bot. Club. 70: 632. 1943. Vergerette du Canada
  7. ^ Flora of China, Erigeron canadensis Linnaeus, Sp. Pl. 2: 863. 1753. 小蓬草 xiao peng cao
  8. ^ Altervista Flora Italiana, Cespica canadese, avoadinha, Berufkraut, Erigeron canadensis L. includes photos and European distribution map
  9. ^ Atlas of Living Australia, Conyza canadensis (L.) Cronquist Canadian Fleabane
  10. ^ Germplasm Resources Information Network: Conyza canadensis
  11. ^ Van Gessel, MJ (2001). "Confirming glyphosate-resistant horseweed (Conyza canadensis) in Delaware". Weed Sci. 49: 703–712. doi:10.1614/0043-1745. 
  12. ^ Kruger, Greg R.; Davis, Vince M.; Weller, Stephen C.; Johnson, William G. (2010). "Growth and Seed Production of Horseweed (Conyza canadensis) Populations after Exposure to Postemergence 2,4-D.". Weed Science. 58 (4): 413–419. doi:10.1614/WS-D-10-00022.1. 
  13. ^ Stevenson, Matilda Coxe 1915 Ethnobotany of the Zuni Indians. SI-BAE Annual Report #30 (p.55)
  • 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[edit]