Cirsium coloradense

(Colorado Thistle)


Cirsium coloradense, Middle Swan River, Summit Co. 5611


Cirsium coloradense, Middle Swan River, Summit Co. 5608


Cirsium coloradense, Middle Swan River, Summit Co. 5599

Scientific Name Cirsium coloradense (Cirsium scariosum var. coloradense) USDA PLANTS Symbol CISC2
Common Name Colorado Thistle ITIS Taxonomic Serial No. 780757
Family Asteraceae (Sunflower) SEINet
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Description Life zones and habitat: Montane to subalpine (7000 to 12500 ft.); moist open areas; meadows, along streams and roadsides.
Plant: Erect biennial or short-lived perennial 12 to 40 inches tall; fleshy, thick single or multiple stalks branched from near base with soft spines.
Leaves: Basal and stem leaves, linear to elliptic 4 to 16 inches long, very wavy, shallow or deeply pinnately-lobed with a broad central midstrip; sessile; smooth above and woolly-hairy below; spiney.
Inflorescence: Dense clusters of one to many flower heads with no ray florets; white to light lavender disk florets 3/4 to 1-3/8 inches long; many long, sharp-pointed phyllaries with spines growing beyond the corolla.
Bloom Period: June to September.
References: "Flora of Colorado" Second Edition by Jennifer Ackerfield, Cirsium scariosum var. coloradense in iNaturalist and in Flora of North America.
Note: In the research document Thistle be a mess: Untangling the taxonomy of Cirsium (Cardueae: Compositae) in North America by Ackerfield, et al, C.scariosum var. coloradense becomes C. coloradense.
BONAP Distribution Map

Map Color Key
Colorado Status:

© Tom Lebsack 2024

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