Page authors: Don Knoke, David Giblin
Ambrosia chamissonis
silver beachweed, beach bur, cutleaf beach bur, silver bur-ragweed

Distribution: Occurring west of the Cascades crest along the marine coastline beaches in Washington; British Columbia, south along the coast, to California.

Habitat: Common on sandy beaches above high tide level.

Flowers: June-September

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern

Pollination: Wind


Monoecious, succulent perennial 2-10 dm. tall, forming large, lax clumps, the stems much branched below the surface, the herbage silvery with appressed hairs.


Leaves mostly alternate, petiolate, the toothed to pinnately dissected blade 2-7 cm. long and 8-40 mm. wide.


Staminate heads sub-sessile, forming congested, leafless, terminal spikes; pistillate heads borne below, in the axils of bracts; fruiting involucre a bur, 6-11 mm. long, with 2-4 series of flattened prickles.



Accepted Name:
Ambrosia chamissonis (Less.) Greene
Publication: Man. Bot. San Francisco. 188. 1894.

Synonyms & Misapplications:
Ambrosia chamissonis (Less.) Greene var. bipinnatisecta (Less.) J.T. Howell [HC]
Ambrosia chamissonis (Less.) Greene var. chamissonis [HC]
Franseria chamissonis Less. ssp. bipinnatisecta (Less.) Wiggins & Stockw.
Franseria chamissonis Less. ssp. chamissonis
Franseria chamissonis Less. var. bipinnatisecta Less.
Franseria chamissonis Less. var. chamissonis
Additional Resources:

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

WA Flora Checklist: Ambrosia chamissonis checklist entry

OregonFlora: Ambrosia chamissonis information

E-Flora BC: Ambrosia chamissonis atlas page

CalPhotos: Ambrosia chamissonis photos

32 photographs:
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