Cirsium barnebyi

This species, which was described in 1981, is accepted by Cronquist (1994), Kartesz (1999), and recent state Floras.

Known from Utah and Colorado; it is reported to be ubiquitous on shale, both Uinta and Green River Formations (Lyon pers com. 2008).
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Occurrences known from Utah and Colorado; it has not been confirmed whether this species is in Wyoming (NatureServe 2008). It is reported to be ubiquitous on shale, both Uinta and Green River Formations (Lyon pers com. 2008).

There are no documented occurrences in the Utah NHP database; however, it is reported to be abundant in the Uinta Basin (Franklin pers com. 2008). There are 34 documented occurrences in Colorado, and more are expected. The species is reported to be ubiquitous on Uinta and Green River shale by Colorado NHP botanists. The Wyoming information of Cronquist (1994) that it is in Carbon County has not been verified.

Native Cirsiums are increasingly at serious risk from a Eurasian flowerhead weevil (Rhinocyllus conicus Froeh.), which was first introduced in 1968 for biocontrol of Eurasian Carduus thistles such as the weedy alien Carduus nutans (musk thistle). The weevil is extending its range to new host species, as well as geographically; it already was released in southern Canada (British Columbia to Quebec) and the western and eastern U.S. (in many states, such as from Washington, California, Utah and Texas to Idaho, Minnesota, New Jersey, Virginia and Tennessee). Some (but not all) native Cirsium species in Colorado, Nebraska and South Dakota - including populations in protected areas - have been shown to be damaged, with quantified decrease in seed production being "severe", over 70-85% loss. Furthermore, Cirsium species are fugitives which generally depend upon current seed production for their establishment and persistence (Louda et al. 1997; Strong 1997; pers. com. [overview talk 99-09-08 at TNC to Plant Conservation Alliance] by Carol Spurrier, BLM Colorado State Office).