Vascular Plants - Asteraceae - Ambrosia:
Ambrosia artemisiifolia
annual ragweed, common ragweed 
Blooms: August - October
Habit: herb
Duration: annual
Origin: Introduced
Distribution: Throughout the United States and the Pacific Northwest
Habitat: Drier areas at low elevations
Species Description:

General: Monoecious, branching annual, variously hairy, 1-10 dm. tall.
Leaves: Leaves opposite below and alternate above, usually bi-pinnatifid, ovate or elliptic in outline, 3-10 cm. long, the lower and middle ones petiolate.
Flowers: 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.
Fruits: Achene
Accepted Name:
Ambrosia artemisiifolia L.
Synonyms:
Ambrosia artemisiifolia L. var. paniculata (Michaux) Blankinship
Ambrosia artemisiifolia L. var. elatior (L.) Descourt.
Ambrosia elatior L.
Ambrosia glandulosa Scheele
Ambrosia monophylla (Walter) Rydberg

Treated in Flora of the PNW as:
Ambrosia artemisiifolia
Additional Resources:

PNW Herbaria Specimens: View list of Ambrosia artemisiifolia specimens in the Consortium of Pacific Northwest Herbaria database.

WTU Herbarium Specimens: View list of Ambrosia artemisiifolia specimens in the WTU Herbarium database.

Washington Flora Checklist: Ambrosia artemisiifolia treatment.

E-Flora BC: Ambrosia artemisiifolia atlas page.

CalPhotos: Ambrosia artemisiifolia images.

USDA Plants Database: Ambrosia artemisiifolia.
Additional photographs of Ambrosia artemisiifolia:
(click on a thumbnail to view larger photo)

Richard Old

Richard Old

Richard Old

Richard Old

Don Knoke, 2005

Don Knoke, 2005

Richard Old

Richard Old

G. D. Carr, 1976

G. D. Carr, 2008

G. D. Carr, 2008

G. D. Carr, 2008

G. D. Carr, 2008

G. D. Carr, 2008

G. D. Carr, 2008
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Washington Native Plant Society
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