Carduus nutans (Musk Thistle)
Family: Asteraceae (Sunflower)
Noxious Weed!
Musk thistle is a biennial noxious weed. The leaves of the rosette usually have silvery-white margins. Stems have wings of leaf material with spines, but the wings are absent from the stem just below the flower head.  Bracts on the flower head are broad and the outer bracts are reflexed. Plants can grow as high as six feet tall.

Vegetation zone:  Plains, Foothills
Time of bloom:  June - September
Origin:  Introduced   Noxious Weed
Eastern Colorado Wildflowers