Cirsium perplexans
Author: (Rydb.) Petrak

Adobe Hills thistle

Asteraceae (Sunflower Family)

Close up of Cirsium perplexans by Peggy Lyon
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Close up of Cirsium perplexans by Peggy Lyon
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Taxonomic Comments

In view of this species' restricted distribution, the common name, Rocky Mountain thistle, is misleading; one would expect a species so named to be widely distributed in the Rocky Mountains. The name Adobe Hills thistle is descriptive of the habitat (Flora of North America 1993+).

Ranks and Status

Global rank: G2G3
State rank: S2S3
Federal protection status: None
State protection status: None

[+] Description and Phenology

Cirsium perplexans by Ann Fenwick
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Cirsium perplexans by Ann Fenwick
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Cirsium perplexans by Heidi Snyder in progress

General description: Taprooted perennial or biennial, 2-10 dm tall, with purplish, striate stems.  Flowers rose or reddish-purple; flower heads about 3 cm high and broad.  Phyllaries spreading to reflexed, with erose tips or spines 1-2 mm long; bracts with distinct glandular back.  Lower leaves oblanceolate, upper leaves lanceolate and clasping, not decurrent; leaves toothed with weak yellow spines (Flora of North America 1993+), Spackman and Anderson 2002, Ackerfield 2012, Weber and Wittmann 2012).

Look Alikes: Cirsium centaureae bracts are narrower and do not have the distinct glandular back, and flowers are ochroleucous to white (Spackman and Anderson 2002).

Phenology: Flowers May-August (Flora of North America 1993+).

[+] Habitat

Habitat of Cirsium perplexans by Terry Bridgman
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Found almost exclusively on barren clay soils or "adobe hills" that are derived from shales of the Mancos or Wasatch formations.  Associated plant communities have been described as pinyon-juniper woodlands, and sagebrush, saltbrush, and mixed shrublands.  Often found in disturbed areas (Panjabi and Anderson 2004, Ackerfield 2012, Weber and Wittmann 2012).

Elevation Range: 4,892 - 8,373 feet (1,491 - 2,552 meters)

[+] Distribution

Distribution of Cirsium perplexans in Colorado.
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Colorado endemic: Yes
Global range: Colorado endemic known from Delta, Mesa, Montrose, Gunnison, Garfield, and Ouray counties in the Colorado and Gunnison River Valleys. Estimated range is 4,981 square kilometers (1,923 square miles), calculated by the Colorado Natural Heritage Program in 2008 in GIS by drawing a minimum convex polygon around the known occurrences.

[+] Threats and Management Issues

Summary results of an analysis of the status of Cirsium perplexans based on several ranking factors. This species was concluded to be “weakly conserved”. From Rondeau et al. 2011.
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The most significant threat to the long-term survival of Cirsium perplexans is from the use of biological control to manage populations of non-native thistles, primarily from the Eurasian weevil Rhinocyllus conicus. The weevil has been found attacking at least 22 native thistles, including C. perplexans. Cirsium perplexans may also be threatened by the use of herbicides used to control non-native thistles. It could be mistaken for a non-native thistle by weed managers who may not know of the presence of this native species. (Spackman Panjabi and Anderson 2004, Dodge 2005).

[+] References

    • Ackerfield, J. 2012. The Flora of Colorado. Colorado State University Herbarium. 433 pp.
    • Flora of North America Editorial Committee, ed. (FNA). 1993+. Flora of North America North of Mexico. Oxford Univ. Press, New York, Oxford.
    • Flora of North America Editorial Committee. 2006. Flora of North America North of Mexico. Vol. 19. Magnoliophyta: Asteridae, part 6: Asteraceae, part 1. Oxford University Press, New York. xxiv + 579 pp.
    • Harrington, H.D. 1954. Manual of the plants of Colorado. Sage Press, Chicago. 666 pp.
    • Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
    • Neely, B., S. Panjabi, E. Lane, P. Lewis, C. Dawson, A. Kratz, B. Kurzel, T. Hogan, J. Handwerk, S. Krishnan, J. Neale, and N. Ripley. 2009. Colorado Rare Plant Conservation Strategy, Developed by the Colorado Rare Plant conservation Initiative. The Nature Conservancy, Boulder, Colorado, 117 pp.
    • Panjabi, S.S. and D.G. Anderson. 2004. Cirsium perplexans (Rydb.) Petrak (Rocky Mountain thistle): a technical conservation assessment. USDA Forest Service, Rocky Mountain Region. Online. Available: (Accessed 2005)
    • Rydberg, P. A. 1905. Studies on the Rocky Mountain Flora XIV. Bullentin of the Torrey Botanical Club 32(3): 123-138.
    • Spackman, S. and D.G. Anderson. 2002. Colorado Rare Plant Field Guide 2002 Update. Unpublished report prepared by the Colorado Natural Heritage Program, Colorado State University, Fort Collins. 26pp.
    • USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
    • Weber, W. A. and R. C. Wittmann. 2012. Colorado Flora, Western Slope, A Field Guide to the Vascular Plants, Fourth Edition. Boulder, Colorado. 532 pp.

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