Page authors: Don Knoke, David Giblin
Conyza canadensis
Canadian fleabane, horseweed

Distribution: Widely distributed on both sides of the Cascades crest in Washington; British Columbia to California, east to the Atlantic Coast.

Habitat: Roadsides, fields, balds, prairies, ditches, wastelots, and other disturbed, open areas at low elevations.

Flowers: July-September

Origin: Native

Growth Duration: Annual, Biennial

Conservation Status: Not of concern

Pollination: Bees, flies, beetles, wasps


Annual or winter annual, usually nearly glabrous, 2-10 dm. tall, the stem erect, unbranched below.


Leaves numerous, narrow, the lower oblanceolate, petiolate, up to 10 cm. long and 1 cm. wide, often deciduous, the other leaves linear and sessile, somewhat hairy.


Heads numerous in an open inflorescence, small; involucre 3-4 mm. high, imbricate; disk flowers yellow, ray flowers white and very short, barely exceeding the pappus.


Achene flattened, about 2 mm. long with white, bristly pappus.

Accepted Name:
Conyza canadensis (L.) Cronquist
Publication: Bull. Torrey Bot. Club. 70: 632. 1943.

Synonyms & Misapplications:
Conyza canadensis (L.) Cronquist var. canadensis
Conyza canadensis (L.) Cronquist var. glabrata (A. Gray) Cronquist
Additional Resources:

PNW Herbaria: Specimen records of Conyza canadensis in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Conyza canadensis checklist entry.

OregonFlora: Conyza canadensis information.

E-Flora BC: Conyza canadensis atlas page.

CalPhotos: Conyza canadensis photos.

USDA Plants: Conyza canadensis information.

30 photographs:
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