[Wikipedia] Origins: Centaurea virgata is a species of Centaurea. It is native to Western Asia. The subspecies C. virgata subsp. squarrosa is known as squarrose knapweed. (link added by Jessica Johnston)
[NPS] Introduction: Squarrose knapweed (Centaurea virgata ssp. squarrosa) is present in Utah, Nevada, California, Oregon, Wisconsin, and Michigan. How it was introduced to North America is unknown. (link added by Jessica Johnston)