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Montana Field Guide

Montana Field Guides

Canada Horseweed - Conyza canadensis
Other Names:  Erigeron canadensis

Native Species

Global Rank: G5
State Rank: S5
C-value: 2


Agency Status
USFWS:
USFS:
BLM:


 

External Links






 
General Description
Taprooted annual. Stems erect, usually unbranched, 10–100 cm. Herbage glabrate to sparsely hirsute, especially on the leaf margins. Leaves cauline, alternate, linear-oblanceolate, 2–8 cm long, short-petiolate, dentate below. Inflorescence narrow to corymbiform, paniculate, leafy-bracted below. Heads numerous, radiate but apparently discoid; involucres campanulate, 2–5 mm high; phyllaries weakly imbricate in 2 to 4 series, green with a tan center and scarious margins, glabrate, linear-lanceolate; receptacle flat, glabrous. Ray flowers 20 to 30, female, white to pink; ligules up to 1 mm long. Disk flowers perfect, 8 to 25, yellow; corolla 2–3 mm long; tube shorter than the throat; style branch appendages deltoid. Pappus of capillary bristles. Achenes oblong, compressed, ca. 1 mm long, sparsely strigose (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range
Montana Range Range Descriptions

Native
 


Range Comments
Native throughout much of temperate North America (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Observations in Montana Natural Heritage Program Database
Number of Observations: 311

(Click on the following maps and charts to see full sized version) Map Help and Descriptions
Relative Density

Recency

 

(Observations spanning multiple months or years are excluded from time charts)



Habitat
Disturbed meadows grasslands, roadsides; plains, valleys (Lesica et al. 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

References
  • Literature Cited AboveLegend:   View Online Publication
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2012. Manual of Montana Vascular Plants. Fort Worth, TX: BRIT Press. viii + 771 p.
  • Additional ReferencesLegend:   View Online Publication
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    • Adhikari, S. 2018. Impacts of dryland farming systems on biodiversity, plant-insect interactions, and ecosystem services. Ph.D. Dissertation. Bozeman, MT: Montana State University. 207 p.
    • Boggs, K. W. 1984. Succession in riparian communities of the lower Yellowstone River, Montana. M.S. Thesis. Montana State University, Bozeman, 107 pp.
    • Burns, E.E. 2017. Genetic and physiological characterization and ecological management of non-target site resistance in multiple herbicide resistant Avena fatua L. Ph.D. Dissertation. Bozeman, MT: Montana State University. 175 p.
    • Cope, M.G. 1992. Distribution, habitat selection and survival of transplanted Columbian Sharp-tailed Grouse (Tympanuchus phasianellus columbianus) in the Tobacco Valley, Montana. M.Sc. Thesis. Bozeman, Montana: Montana State University. 60 p.
    • DuBois, K.L. 1979. An inventory of the avifauna in the Long Pines of Southeastern Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 113 p.
    • Eggers, M.J.S. 2005. Riparian vegetation of the Montana Yellowstone and cattle grazing impacts thereon. M.Sc. Thesis. Montana State University, Bozeman, MT. 125 p.
    • Gobeille, J.E. 1992. The effect of fire on Merriams turkey brood habitat in southeastern Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 61 p.
    • Harvey, S.J. 1990. Responses of steppe plants to gradients of water soil texture and disturbance in Montana, U.S.A. Ph.D. Thesis. Bozeman, MT: Montana State University. 34 p.
    • Jones, W. W. 1901. Preliminary flora of Gallatin County. M.S. Thesis. Bozeman, MT: Montana State College. 78 pp.
    • King, L.A. 1980. Effects of topsoiling and other reclamation practices on nonseeded species establishment on surface mined land at Colstrip, Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 129 p.
    • Lesica, P., M.T. Lavin, and P.F. Stickney. 2022. Manual of Montana Vascular Plants, Second Edition. Fort Worth, TX: BRIT Press. viii + 779 p.
    • Martinka, R.R. 1970. Structural characteristics and ecological relationships of male blue grouse (Dendragapus obscurus (Say)) territories in southwestern Montana. Ph.D Dissertation. Bozeman, MT: Montana State University. 73 p.
    • Meier, G.A. 1997. The colonization of Montana roadsides by native and exotic plants. M.Sc. Thesis. Bozeman, MT: Montana State University. 45 p.
    • Quire, R.L. 2013. The sagebrush steppe of Montana and southeastern Idaho shows evidence of high native plant diversity, stability, and resistance to the detrimental effects of nonnative plant species. M.Sc. Thesis. Bozeman, MT: Montana State University. 124 p.
    • Rundquist, V.M. 1973. Avian ecology on stock ponds in two vegetational types in north-central Montana. Ph.D. Dissertation. Bozeman, MT: Montana State University. 112 p.
    • Seipel, T.F. 2006. Plant species diversity in the sagebrush steppe of Montana. M.Sc. Thesis. Bozeman, MT: Montana State University. 87 p.
    • Thompson, W. L. 1993. Ecology of Merriam's Turkeys in relation to burned and logged areas in southeastern Montana. Ph.D. Dissertation. Bozeman, MT: Montana State University. 195 p.
  • Web Search Engines for Articles on "Canada Horseweed"
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Citation for data on this website:
Canada Horseweed — Conyza canadensis.  Montana Field Guide.  .  Retrieved on , from