Russian knapweed
Rhaponticum repens

Russian knapweed (Rhaponticum repens) is an invasive plant. It was first detected in Michigan in 1928.

Russian knapweed is an aggressive, long-lived perennial that thrives in both irrigated and arid environments, and in cropland, pastures, rangeland, shrubland, and wasteland. It is difficult to control in alfalfa, clover, other forage crops, and pastures. It reduces wildlife habitat and suppresses the growth of other plants. .
Summaries of State Plant Protection Laws and Regulations
Montana   Wyoming