Page authors: Don Knoke, David Giblin
Xanthium strumarium
Canada cocklebur, common cocklebur

Distribution: Occurring chiefly east of the Cascades crest in Washington; British Columbia to California, east across North America to the Atlantic Coast

Habitat: Wet meadows, shorelines, and disturbed open areas where moist.

Flowers: July-October

Origin: Native

Growth Duration: Annual

Conservation Status: Not of concern

Pollination: Bees, flies, beetles, wasps


Monoecious, coarse annual with alternate leaves, 1-5 dm. tall


Leaves broadly ovate to sub-orbicular, generally cordate or deltoid at the base, with long petioles and without spines.


Staminate heads uppermost, many-flowered; involucre of separate bracts; receptacle cylindric, chaffy; involucre of the pistillate heads completely enclosing the 2 flowers, forming a 2-chambered bur with hooked prickles; pappus none.


Achenes thick, solitary in the chambers of the bur.

Accepted Name:
Xanthium strumarium L.
Publication: Sp. Pl. 2: 987. 1753.

Synonyms & Misapplications:
Xanthium strumarium L. var. canadense (Mill.) Torr. & A. Gray [HC]
Xanthium strumarium L. var. glabratum (DC.) Cronquist [HC]
Xanthium strumarium L. var. oviforme (Wallr.) M. Peck
Xanthium strumarium L. var. pensylvanicum (Wallr.) M. Peck
Xanthium strumarium L. var. strumarium
Xanthium strumarium L. var. wootonii (Cockerell) W.C. Martin & C.R. Hutchins, invalidly published
Additional Resources:

PNW Herbaria: Specimen records of Xanthium strumarium in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Xanthium strumarium checklist entry.

OregonFlora: Xanthium strumarium information.

E-Flora BC: Xanthium strumarium atlas page.

CalPhotos: Xanthium strumarium photos.

USDA Plants: Xanthium strumarium information.

37 photographs:
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