silver burweed (silver burr ragweed)
Asteraceae (Aster family)
Introduction to Vascular Plants
Photograph
© Dawn Hanna (Photo ID #10550)
Species Information
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.
Illustration
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
Ecology
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 |
||
|
Avg |
Min |
Max |
|
| Elevation
(metres) |
193 | 0 | 1020 |
| Slope
Gradient (%) |
1 | 0 | 5 |
|
Aspect (degrees) |
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
|
|||
Habitat and Range
Moist to mesic coastal sandy or gravelly upper beaches and shorelines in the lowland zone; common in coastal BC; S to CA.Status Information
Synonyms
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 Keys
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 |