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Montana Field Guide

Montana Field Guides

Canada Horseweed - Conyza canadensis


Global Rank: G5
State Rank: S5

Agency Status
USFWS:
USFS:
BLM:
MNPS Threat Rank:
C-value: 2

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 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

Species Range
Present
 


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

Summary of Observations Submitted for Montana
Number of Observations: 52

(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 2012. Manual of Montana Vascular Plants. BRIT Press. Fort Worth, TX).

References
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Citation for data on this website:
Canada Horseweed — Conyza canadensis.  Montana Field Guide.  .  Retrieved on , from