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

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

Introduction to Vascular Plants

General:
Perennial herb from long, creeping rhizomes; stems leafy, spreading-hairy, stout, branched just below the surface, forming large, lax clumps 20-160 cm tall.

Leaves:
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.

Flowers:
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.

Fruits:
Achenes enclosed within the involucral bracts; pappus lacking.

Source: The Illustrated Flora of British Columbia

If more than one illustration is available for a species (e.g., separate illustrations were provided for two subspecies) then links to the separate images will be provided below. Note that individual subspecies or varietal illustrations are not always available.

Illustration 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
Site Information	Avg	Min	Max
Elevation (metres)	193	0	1020
Slope Gradient (%)	1	0	5
Aspect (degrees) [0 - N; 90 - E; 180 - S; 270 - W]	92	50	135
Soil Moisture Regime (SMR) [0 - very xeric; 4 - mesic; 8 - hydric]	2	1	6
Modal Nutrient Regime Class	A
# of field plots species was recorded in:	12
Modal BEC Zone Class	CWH
All BEC Zones (# of stations/zone) species was recorded in	BWBS(1), CWH(9), MS(2)
Source: Klinkenberg 2013

Origin Status	Provincial Status	BC List (Red Blue List)	COSEWIC
Native	S5	Yellow	Not Listed

BC Ministry of Environment: BC Species and Ecosystems Explorer.

1. Involucres with 2-4 series of short, sharp spines; leaves mostly alternate................A. chamissonis

1. Involucres with a single series of short spines or tubercles above the middle; leaves, or at least the lower ones, opposite.

2. Plants annual from fibrous roots; leaves mostly stalked, mostly twice pinnatifid; involucres with short spines..................A. artemisiiifolia

2. Plants perennial from creeping roots; leaves short-stalked or nearly unstalked, only once-pinnatifid; involucres with tubercles......................A. psilostachys

Source: Illustrated Flora of British Columbia

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