Cirsium arvense

(Canada Thistle)

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Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9347

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Cirsium arvense, Frisco Peninsula, Summit Co. 7647/7657

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Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9326

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Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9340

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Cirsium arvense, Frisco Peninsula, Summit Co. 7635

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Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9363

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Stem leaf, Cirsium arvense, Silver Shekel, Breckenridge, Summit Co. 9353

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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
Click Here
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 2022

Banner photo: Ten Mile Range and Rhodiola integrifolia (King’s Crown) in Summit County