CPC Plant Profile: Cedar Rim Thistle
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Plant Profile

Cedar Rim Thistle (Cirsium pulcherrimum var. aridum)

This rare thistle can be found at the base of bluffs, like this one in Fremont Co., Wyoming. Photo Credit: Charmaine Refsdal
  • Global Rank: G2 - Imperiled
  • Legal Status: N/A
  • Family: Asteraceae
  • State: WY
  • Nature Serve ID: 154329
  • Date Inducted in National Collection: 12/01/2021

Thistles are more often thought of as weeds than plants in need of conservation, but the Cedar Rim thistle is one of a handful with very limited distributions. Known only known from the cold desert country of central Wyoming, Cedar Rim thistle grows on barren hills and slopes where its silvery, woolly foliage protects it from intense heat, wind and solar radiation. Many of its associates are themselves rare plants.

Participating Institutions
Nature Serve Biotics
  • 05/02/2017

A recently described species, currently known from only 11 occurrences in central and westcentral Wyoming. Potential habitat may occur in northeastern Utah and northwestern Colorado.

Jim Locklear
  • 01/01/2010

Construction associated with oil and gas development. Off-road vehicle damage. Livestock trampling.

Jim Locklear
  • 01/01/2010


Jim Locklear
  • 01/01/2010

Clarification of taxonomic status. Population monitoring. Exact habitat characterization. Additional survey work.

Jim Locklear
  • 01/01/2010

Seed germination studies. Additional seed banking.


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Taxon Cirsium pulcherrimum var. aridum
Authority (Dorn) D.J. Keil
Family Asteraceae
CPC Number 5001
ITIS 780852
Common Names Cedar Rim thistle | desert thistle
Associated Scientific Names Cirsium aridum | Cirsium pulcherrimum var. aridum
Distribution Limited to the Wind River and Green River basins of central Wyoming (Carbon, Fremont and Sublette counties).
State Rank
State State Rank
Wyoming S2

Barren, chalky hills, gravelly slopes, and fine textured, sandy-shaly draws. Occurs in cushion plant communities within more densely vegetated cold desert shrubland dominated by big sagebrush (Artemisia tridentata). Elevation 6700-7200 ft. (Fertig 1994)

Ecological Relationships

One population occurs with the very rare plant, desert yellowhead (Yermo xanthocephalus).

Common Name Name in Text Association Type Source InteractionID

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