Cirsium arvense

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Scientific Name Cirsium arvense USDA PLANTS Symbol CIAR4
Common Name Canada Thistle ITIS Taxonomic Serial No. 36335
Family Asteraceae (Sunflower) SEINet
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Description Life zones and habitat: Plains to montane. 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 October.
References: "Wildflowers of the Rocky Mountains" by Carl Schreier and SEINet.
BONAP Distribution Map

Colorado Status:
Noxious Weed

© Tom Lebsack 2021