Common Groundsel
Senecio vulgaris

Family: Sunflower (Asteraceae)
AKA: Common Butterweed, Old-man-in-the-Spring
Photo taken on: August 1, 2008
Location: Almont, GV, CO
Life Zones: Plains to foothills
Habitat: Gardens, disturbed areas

A weed growing to 15" with loose clusters of rayless flowers and twisted stems.

Flora of North America reference.