Page authors: Don Knoke, David Giblin
Ambrosia artemisiifolia
annual ragweed, common ragweed

Distribution: Occurring on both sides of the Cascades crest in Washington; Alaska to California, east across North America to the Atlantic Coast.

Habitat: Roadsides, fields, pastures, wastelots, and other dry, disturbed, open areas at low elevations.

Flowers: August-October

Origin: Introduced from eastern North America

Conservation Status: Not of concern


Monoecious, branching annual, variously hairy, 1-10 dm tall.


Leaves opposite below and alternate above, usually bi-pinnatifid, ovate or elliptic in outline, 3-10 cm. long, the lower and middle ones petiolate.


Staminate heads small, numerous, short-pedunculate, in an elongate, bractless, spike-like inflorescence; pistillate heads borne below, in the axils of bracts; fruiting involucre a short-beaked bur, 3-5 mm. long, with several short, sharp spines.



Accepted Name:
Ambrosia artemisiifolia L.
Publication: Sp. Pl. 2: 988. 1753.

Synonyms & Misapplications:
Ambrosia artemisiifolia L. var. elatior (L.) Descourtilz
Ambrosia artemisiifolia L. var. paniculata (Michx.) Blank.
Ambrosia elatior L.
Ambrosia glandulosa Scheele
Ambrosia monophylla (Walter) Rydb.
Additional Resources:

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

WA Flora Checklist: Ambrosia artemisiifolia checklist entry.

E-Flora BC: Ambrosia artemisiifolia atlas page.

CalPhotos: Ambrosia artemisiifolia photos.

USDA Plants: Ambrosia artemisiifolia information.

25 photographs:
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