Page author: David Giblin
Ambrosia acanthicarpa
flat spine bur-ragweed, annual bursage, bur ragweed
WTU specimens
Other herbaria

Distribution: Chiefly east of the Cascades, but widespread in western United States, to Texas and the Dakotas

Habitat: Weedy native in dry areas at low elevations

Flowers: July-October

Origin: Native

Conservation Status: Not of concern

Description:
General:

Monoecious, branching annual, 1-8 dm. tall, coarsely rough-hairy.

Leaves:

Leaves mostly alternate, petiolate, bipinnatifid, the blade 2-8 cm. long.

Flowers:

Heads numerous in elongate, terminal racemes, sometimes chiefly staminate or chiefly pistillate; staminate heads 2-4 mm. wide, short-pedunculate, not subtended by leaves; pistillate involucres solitary or clustered in the upper leaf axils, the burs 5-10 mm. long, with several series of flattened, divergent spines

Fruits:

Achene

Accepted Name:
Ambrosia acanthicarpa Hook.
Publication: Fl. Bor.-Amer. 1: 309. 1833. 1833.

Synonyms & Misapplications:
Franseria acanthicarpa (Hook.) Coville
Additional Resources:

PNW Herbaria: Specimen records of Ambrosia acanthicarpa in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Ambrosia acanthicarpa checklist entry.

E-Flora BC: Ambrosia acanthicarpa atlas page.

CalPhotos: Ambrosia acanthicarpa photos.

USDA Plants: Ambrosia acanthicarpa information.

12 photographs:
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