Machaeranthera bigelovii or Machaeranthera pattersonii
(Bigelow's Tansyaster)
Family: Asteraceae (Sunflower)
  
Machaeranthera bigelovii  is a common purple daisy from the foothills to subalpine elevations. Bracts are reflexed and glandular. Most sources list M. bigelovii and M. pattersonii as synonyms for a single species, but Weber has split them into separate species.

Compare to Machaeranthera canescens, which grows on the plains. The bracts below the flower heads on M. canescens are less glandular.
The two species are believed to hybridize.

Vegetation zone:  Foothills, Montane, Subalpine
Time of bloom:  June - October
Origin:  Native
Eastern Colorado Wildflowers