I . SUMMARY 



Cirsium subniveum is a native, perennial thistle 

 (Sunflower Family). The species 1 known range extends 

 from central Idaho to Jackson Hole, Wyoming, into 

 Montana (Beaverhead and Madison counties) , Utah (Box 

 Elder, Cache, Rich and Sanpete counties) , and northeast 

 Oregon (Hitchcock et al. 1955, Welsh et al. 1987) . 



During field surveys conducted in 1991, seven new 

 occurrences of C. subniveum were located, and 

 additional subpopulations were added to three 

 previously known locations. In addition, two more 

 locations were entered from Montana Rare Plant Project 

 (herbarium) data. This brings the total number of 

 occurrences of C. subniveum in Montana to twelve; five 

 in Madison County, and seven in Beaverhead County. 

 Populations occur on lands managed by the Bureau of 

 Land Management, Dillon Resource Area; U.S. Forest 

 Service, Beaverhead National Forest; and on private 

 lands. 



One factor controlling the distribution of Cirsium 

 subniveum in Montana is its association with unstable 

 rock and gravel slides. However, the species does not 

 appear to be tied to a particular geologic parent 

 material. In Montana, C. subniveum populations occur 

 in Pseudotsuga menziesii/Festuca idahoensis and 

 Pseudotsuaa menziesii/Juniperus communis habitat types 

 as described by Pfister et al. (1977) . 



A number of the populations are in historic mining 

 districts that have seen some renewed attention by 

 geological interests in recent years. Land managers 

 should take these sites into consideration whenever 

 evaluating activities that might effect these 

 populations. 



Only a portion of the potential habitat of C. subniveum 

 could be surveyed in the time allowed. Further survey 

 work in the Tendoy and Snowcrest ranges, and 

 particularly in the Gravelly Range, may reveal that C. 

 subniveum is more common in this portion of the state. 

 Due to small population sizes and low densities, C. 

 subniveum should remain on the U.S. Forest Service, 

 Region 1 sensitive species list. 



