Cirsium arvense
(Canada Thistle)
Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9347
Cirsium arvense, Frisco Peninsula, Summit Co. 7647/7657
Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9326
Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9340
Cirsium arvense, Frisco Peninsula, Summit Co. 7635
Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9363
Stem leaf, Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9353
Basal leaves, Cirsium arvense, Frisco Peninsula, Summit Co. 7634
| Scientific Name | Cirsium arvense | USDA PLANTS Symbol | CIAR4 |
| Common Name | Canada Thistle | ITIS Taxonomic Serial No. | 36335 |
| Family | Asteraceae (Sunflower) | SEINet Reference |
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| Description |
Life zones and habitat: Plains to montane (4000 to 9800 ft.); disturbed areas, pastures, roadsides, croplands. Plant: Erect perennial, 1 to 4 feet tall; stems are grooved and branched near the top. Leaves: Oblong to elliptic, 1 to 12 inches long, with edges entire, shallow or deeply-pinnately-lobed with spines. Inflorescence: Lavender composite flower heads about 1-inch across; green to purplish bracts. Male and female flowers on separate plants. Bloom Period: June to September. References: "Flora of Colorado" by Jennifer Ackerfield, "Wildflowers of the Rocky Mountains" by Carl Schreier and SEINet. |
BONAP Distribution Map Map Color Key |
Colorado Status: Noxious Weed |
© Tom Lebsack 2024
Banner photo: Ten Mile Range and Rhodiola integrifolia (King’s Crown) in Summit County