Cirsium species

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These thistle species are grouped under White flowers, because of the overall appearance of the flower heads, even though the disk florets range from yellow to purple to brown. The IDs are believed to be correct but these can be highly variable species. One of the identifiers is their habitat.

Scientific Name Cirsium eatonii USDA PLANTS Symbol CIEA
Common Name Eaton's Thistle, Mountaintop Thistle ITIS Taxonomic Serial No. 36365
Family Asteraceae (Sunflower) SEINet
Reference
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Description Life zones and habitat: Montane to alpine (9500 to 13000 ft.); open areas, common on rocky alpine slopes.
Plant: Upright biennial/perennial, 8 to 28+ inches tall.
Leaves: Oblong leaves 1/2 to 2 inches wide and 4 to 14 inches long, deeply pinnately-lobed, with spines at the tip of each lobe; smooth or slightly hairy above, woolly-hairy below.
Inflorescence: Spiny bracts around flower heads give white appearance to flowers; central disk florets lavender to purple 3/4 to 1 inch long; no ray flowers.
Bloom Period: July to September.
References: "Flora of Colorado" by Jennifer Ackerfield, and others.
BONAP Distribution Map

Colorado Status:
Native
Scientific Name Cirsium eatonii var. eriocephalum (Cirsium scopulorum) USDA PLANTS Symbol CISC3
Common Name Alpine Thistle, Mountain Thistle, Frosty Ball ITIS Taxonomic Serial No. 780840
Family Asteraceae (Sunflower) SEINet
Reference
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Description Life zones and habitat: Subalpine and alpine (10500 to 13500 ft.); open areas, meadows; windswept alpine ridges.
Plant: Upright perennial, 8 to 32 inches tall; stout, spiney stem.
Leaves: Basal and stem leaves, lanceolate 1 to 13 inches long, deeply pinnately-incised with lobes tipped by spines 1/2-inch long; smooth above, woolly-hairy below.
Inflorescence: Clusters of very hairy flower heads, often nodding; densely-hairy bracts with spines 3/8 to 3/4-inch long; white to yellow or light pink disk florets in the center; no ray flowers.
Bloom Period: July to September.
References: "Flora of Colorado" by Jennifer Ackerfield, "Guide to Colorado Wildflowers" by G.K. Guennel and SEINet.
BONAP Distribution Map

Colorado Status:
Native
Scientific Name Cirsium scariosum USDA PLANTS Symbol CISC2
Common Name Meadow Thistle ITIS Taxonomic Serial No. 36143
Family Asteraceae (Sunflower) SEINet
Reference
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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: Stemless or upright biennial/perennial, up to 40 inches tall; fleshy, thick single or multiple stalks branched from near base.
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; white to light lavender disk florets 3/4 to 1-3/8 inches long; pointed phyllaries with spines and teeth; no ray flowers.
Bloom Period: June to September.
References: "Flora of Colorado" by Jennifer Ackerfield and others.
BONAP Distribution Map

Colorado Status:
Native



© Tom Lebsack 2020