Acosta diffusa or Centaurea diffusa
(Diffuse Knapweed)
Family: Asteraceae (Sunflower)
Noxious Weed!
  
Diffuse knapweed is a biennial weed. Flowers are usually white but are sometimes lavendar. Bracts below the flowers are reflexed and have bristles along the margins. Stems divide into many branches, giving mature plants a shrublike structure. Diffuse knapweed is a noxious weed that should be aggressively controlled.

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