E-Flora BC: Electronic Atlas of the Flora of British Columbia

Conyza canadensis (L.) Cronquist
horseweed (Canadian fleabane; Canadian horseweed)
Asteraceae (Aster family)

Introduction to Vascular Plants

© Bryan Kelly-McArthur  Email the photographer   (Photo ID #85702)

E-Flora BC Static Map
Distribution of Conyza canadensis
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Species Information

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Annual herb from a taproot; stems erect, usually single, more or less glabrous, 0.2-1.0 m tall.
Basal leaves lacking; stem leaves linear to linear-lanceolate or the lowermost oblanceolate, stalked, 2-10 cm long, 2-8 mm wide, glabrous.
Heads with ray and disk flowers, numerous in an open, leafy, branched, usually cylindric inflorescence; involucres 3-4 mm tall; involucral bracts graduated, glabrous to sparsely stiff-hairy, with a conspicuous central glandular area and narrow, more or less papery margins; ray flowers white, numerous, inconspicuous, barely exceeding the pappus; disk flowers few.
Achenes stiff-hairy; pappus of dirty-whitish, slender hairs.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Fruit/Seed characteristics:
Colour: Brown
Present over the
Source:  The USDA

Habitat / Range

Mesic to dry roadsides and disturbed areas in the lowland, steppe and montane zones; frequent in S BC; introduced, native range uncertain.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Conyza canadensis

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 370 797 1300
Slope Gradient (%) 0 20 70
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
66 176 332
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
0 2 7
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BG(4), ESSF(1), ICH(1), IDF(20), PP(2)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Conyza canadensis var. glabrata (A. Gray) Cronquist
Erigeron canadensis var. glabratus Gray

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References