Cirsium arvense (L.) Scop.
Canada thistle
Asteraceae (Aster family)
Introduction to Vascular Plants
Canada thistle
Asteraceae (Aster family)
Introduction to Vascular Plants
Species Information
General:
Perennial herb from deep, wide-spreading roots and creeping underground stems; stems erect, glabrous, branched above, 0.3-2.0 m tall.
Leaves:
Basal leaves soon deciduous; stem leaves alternate, lance-shaped on the lower stem, becoming broader upwards, up to 20 cm long and 7 cm wide, irregularly lobed, spiny-toothed, glabrous or green above, densely white-hairy beneath.
Flowers:
Heads discoid, unisexual (composed of either male or female flowers) numerous, small, solitary at the ends of branches in an open inflorescence; involucres 1-2 (rarely 2.5) cm tall; involucral bracts glabrous or slightly cobwebby, outer ones egg-shaped, awl-tipped, inner ones progressively longer and lanceolate, unarmed; disk flowers pink-purple, rarely white, female ones 23-26 mm long, the male ones 12-14 mm long.
Fruits:
Achenes 2.5-4 mm long; pappus tawny, exceeding the corollas.
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
Ecological Framework for Cirsium arvense
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)
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) |
795 | 0 | 2200 |
| Slope
Gradient (%) |
11 | 0 | 90 |
|
Aspect (degrees) |
199 | 0 | 360 |
| Soil
Moisture Regime (SMR) [0 - very xeric; 4 - mesic; 8 - hydric] |
4 | 1 | 8 |
| Modal
Nutrient Regime
Class |
C | ||
| #
of field plots species was recorded in: |
308 | ||
| Modal
BEC Zone Class |
CWH | ||
|
All BEC Zones (# of stations/zone) species was recorded in |
BG(12), CDF(2), CWH(77), ESSF(18), ICH(36), IDF(75), MS(29), PP(15), SBS(23), SWB(3) | ||
|
Source:
Klinkenberg 2013
|
|||
Habitat and Range
Mesic to dry roadsides, fields and disturbed areas in the lowland, steppe and montane zones; common in W, SC and NE BC; introduced from Eurasia.Status Information
Synonyms
Synonyms and Alternate Names:
Breea arvensis Less.
Breea incana (Gmel.) W.A. Weber
Carduus arvensis (L.) Robson
Cirsium arvense var. argenteum (Vest) Fiori
Cirsium arvense var. horridum Wimmer & Grab.
Cirsium arvense var. horridum Wimm. & Grab.
Cirsium arvense var. integrifolium Wimmer & Grab.
Cirsium arvense var. mite Wimmer & Grab.
Cirsium arvense var. vestitum Wimmer & Grab.
Cirsium incanum (Gmel.) Fisch.
Cirsium setosum (Willd.) Bess. ex Bieb.
Serratula arvensis L.