E-Flora BC: Electronic Atlas of the Flora of British Columbia

Ambrosia chamissonis (Less.) Greene
silver burweed (silver burr ragweed)
Asteraceae (Aster family)

Introduction to Vascular Plants

© Dawn Hanna  Email the photographer   (Photo ID #10550)

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Distribution of Ambrosia chamissonis
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Species Information

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Perennial herb from long, creeping rhizomes; stems leafy, spreading-hairy, stout, branched just below the surface, forming large, lax clumps 20-160 cm tall.
Succulent, mostly alternate, oblong to rounded in outline, about 4-14 cm long with stalks 2-7 cm long, the blades pinnately dissected or rarely simple and toothed, finely whitish- or silvery-haired.
Male (sterile) heads nearly unstalked or short-stalked, 4-6 mm wide, in congested, leafless, terminal spikes about 8 cm long; female (fruiting) heads egg-shaped, 1-flowered;fruiting involucres 1-beaked, 6-11 mm long, glandular and finely hairy burs with 2-4 series of spines or prickles.
Achenes enclosed within the involucral bracts; pappus lacking.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Moist to mesic coastal sandy or gravelly upper beaches and shorelines in the lowland zone; common in coastal BC; S to CA.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Ambrosia chamissonis

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 0 193 1020
Slope Gradient (%) 0 1 5
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
50 92 135
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
1 2 6
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BWBS(1), CWH(9), MS(2)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Ambrosia chamissonis var. bipinnatisecta (Less.) J.T. Howell
Franseria chamissonis Less.
Franseria chamissonis subsp. bipinnatisecta (Less.) Wiggins & Stockw.
Franseria chamissonis var. bipinnatisecta Less.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References