''Cirsium perplexans'' is a species of flowering plant in the family

Asteraceae The family Asteraceae, alternatively Compositae, consists of over 32,000 known species of flowering plants in over 1,900 genera within the order Asterales. Commonly referred to as the aster, daisy, composite, or sunflower family, Compositae w ...

known by the common names Rocky Mountain thistle and Adobe Hills thistle. It is

endemic Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found elsew ...

Colorado Colorado (, other variants) is a state in the Mountain West subregion of the Western United States. It encompasses most of the Southern Rocky Mountains, as well as the northeastern portion of the Colorado Plateau and the western edge of t ...

in the United States, where it occurs in the

and Gunnison River Valleys in the

Rocky Mountains The Rocky Mountains, also known as the Rockies, are a major mountain range and the largest mountain system in North America. The Rocky Mountains stretch in straight-line distance from the northernmost part of western Canada, to New Mexico in ...

.Panjabi, S.S. and D.G. Anderson (2004, August 31)
''Cirsium perplexans'' (Rydb.) Petrak (Rocky Mountain thistle): A technical conservation assessment.
nline USDA Forest Service, Rocky Mountain Region. This species is a biennial herb growing up to one meter tall from a taproot. The stems are coated thinly in webby fibers. The leaves are up to 30 centimeters long by 6 wide. They are sometimes unlobed but have toothed margins. The leaves have woolly fibers, especially on the undersides. The

flower heads A pseudanthium (Greek for "false flower"; ) is an inflorescence that resembles a flower. The word is sometimes used for other structures that are neither a true flower nor a true inflorescence. Examples of pseudanthia include flower heads, compos ...

contain long lavender or purplish florets. The fruit is an

achene An achene (; ), also sometimes called akene and occasionally achenium or achenocarp, is a type of simple dry fruit produced by many species of flowering plants. Achenes are monocarpellate (formed from one carpel) and indehiscent (they do not ope ...

which may exceed 2 centimeters in length including its pappus.''Cirsium perplexans''.
Flora of North America. This species is found in western Colorado, usually on open outcrops of clay-based soils called "adobe hills". Habitat types include pinyon-juniper woodland, sagebrush, saltbrush, and shrublands. Dominant plant species include '' Pinus edulis'' (pinyon pine), '' Juniperus osteosperma'' (Utah juniper), '' Artemisia tridentata'' (big sagebrush), ''Artemisia tridentata'' ssp. ''wyomingensis'' (Wyoming sagebrush), '' Atriplex confertifolia'' (saltbush), '' Amelanchier utahensis'' (Utah serviceberry), and '' Quercus gambelii'' (Gambel's oak). The thistle grows in open areas that are sparsely vegetated. It can tolerate some disturbance and may occur on roadsides. The main threat to this species is probably

biological pest control Biological control or biocontrol is a method of controlling pests, such as insects, mites, weeds, and plant diseases, using other organisms. It relies on predation, parasitism, herbivory, or other natural mechanisms, but typically also invo ...

agents released to control non-native thistle species. For example, the

weevil Weevils are beetles belonging to the Taxonomic rank, superfamily Curculionoidea, known for their elongated snouts. They are usually small, less than in length, and Herbivore, herbivorous. Approximately 97,000 species of weevils are known. They b ...

'' Rhinocyllus conicus'' was released to control musk thistle, ''

Carduus nutans ''Carduus nutans'', with the common names musk thistle, nodding thistle, and nodding plumeless thistle, is a biennial plant in the daisy and sunflower family Asteraceae. It is native to regions of Eurasia. Description ''Carduus nutans'' is usual ...

'', but once in the wild it also attacked many native species, including native thistles such as ''C. perplexans''. The weevil ''

Larinus planus ''Larinus planus'' is an insect of the Curculionidae ("true" weevil) family. They are oval shaped, dark brown or black, and about long. While native to Europe, it is also common in North America. It feeds on floral buds, primarily of thistles, w ...

'' has been released near the habitat of ''C. perplexans'' for the biological control of '' Cirsium arvense''. It is not yet known if this weevil will attack ''C. perplexans''. In addition,

herbicide Herbicides (, ), also commonly known as weedkillers, are substances used to control undesired plants, also known as weeds.EPA. February 201Pesticides Industry. Sales and Usage 2006 and 2007: Market Estimates. Summary in press releasMain page fo ...

s used to control invasive thistles may harm native species.''Cirsium perplexans''.
NatureServe. Other threats include excessive disturbance of the habitat. The thistle can tolerate some disturbance but off-road vehicle use can cause extensive degradation of the habitat. Road traffic may also be destructive.

Introduced species An introduced species, alien species, exotic species, adventive species, immigrant species, foreign species, non-indigenous species, or non-native species is a species living outside its native distributional range, but which has arrived there ...

of plants may be a threat, including ''

Bromus inermis ''Bromus inermis'' is a species of the true grass family ( Poaceae). This rhizomatous grass is native to Europe Europe is a large peninsula conventionally considered a continent in its own right because of its great physical size and the ...

'' (smooth brome) and ''

Melilotus officinalis ''Melilotus officinalis'', known as sweet yellow clover, yellow melilot, ribbed melilot and common melilot, is a species of legume native to Eurasia and introduced in North America, Africa, and Australia. Description ''Melilotus officinalis'' c ...

'' (yellow sweet clover).

References

{{Taxonbar, from=Q5122069 perplexans Flora of Colorado Flora of North America