Scientific Name : Cirsium perplexans
Author : (Rydb.) Petrak
NatureServe Explorer
Common Name : Adobe Hills Thistle
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Taxonomy
Asteraceae (sunflower family)
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
State Rank : S3
State Rank Reason : Cirsium perplexans is endemic to the Colorado and Gunnison River Valleys in western Colorado, USA. There are 43 occurrences but ten of those are historical. 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 species appears to be stable and possibly increasing at some occurrences, and is considered moderately vulnerable to climate change.
U.S. Endangered Species Act : none
Colorado Threatened and Endangered List : none
Other Statuses : SWAP Tier 2
Description and Phenology
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+).
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Habitat
Found on barren gray shale slope above intermittent stream bed (Colorado National Heritage Program 1996) and adobe hills (Weber 1996).
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Elevation Range:
5,014 - 8,345 feet (1,528 - 2,544 meters)
Distribution
Colorado Endemic:
Yes
Range:
Cirsium perplexans is a Colorado (USA) endemic known from Delta, Mesa, Montrose, Gunnison, Garfield, and Ouray counties in the Colorado and Gunnison River Valleys. Estimated range extent in Colorado of 6354 square kilometers was calculated in GeoCAT using occurrence data provided by the Colorado Natural Heritage Program (2023).
Click on map to enlarge |
Threats and Management Issues
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 (Panjabi and Anderson 2004). This species is considered to have moderate adaptive capacity and is expected to be slightly to moderately vulnerable to climate change under both RCP 4.5 and 8.5 scenarios, as assessed for the 2025 Colorado State Wildlife Action Plan (CNHP 2025).
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. |
References
- Ackerfield, J. 2015. Flora of Colorado. BRIT Press, Botanical Research Institute of Texas, Fort Worth, TX. 818 pp.
- Colorado Natural Heritage Program (CNHP). 2025. Climate Change Vulnerability Assessment of Colorado Tier 1 and Tier 2 Plant Species of Greatest Conservation Need (SCGN) for the 2025 Colorado State Wildlife Action Plan. Colorado Natural Heritage Program, Colorado State University, Fort Collins, CO.
- Flora of North America Editorial Committee, ed. (FNA). 1993+. Flora of North America North of Mexico. Oxford Univ. Press, New York, Oxford.
- Handwerk, J., L. Grunau, and S. Panjabi. 2015. Colorado Wildlife Action Plan: 2015 Rare Plant Addendum. Colorado Natural Heritage Program, Colorado State University, Fort Collins, Colorado, USA.
- 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: http://www.fs.fed.us/r2/projects/scp/assessments/cirsiumperplexans.pdf (Accessed 2005)
- Rydberg, P. A. 1905. Studies on the Rocky Mountain Flora XIV. Bullentin of the Torrey Botanical Club 32(3): 123-138.
- USDA, NRCS. 2013. The PLANTS Database. National Plant Data Team, Greensboro, NC 27401-4901 USA.
- USDA, NRCS. 2022. 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.
Biotics Export Date : September, 2026
