Sonchus oleraceus (Common Sowthistle) Family: Asteraceae (Sunflower)
The leaves of Sonchus oleraceus are deeply lobed and are broadest toward the tip. Spines on the leaf teeth are relatively weak. Bracts below of the flower heads are smooth and the closed heads are broadest toward the base. Plants have a milky juice.

Compare to Sonchus arvensis, which has glandular hairs on the outside of the flower heads and narrower leaves.
Compare to Sonchus asper, which has spiny leaves with large lobes clasping the stem and lacks glandular hairs on the flower head bracts.

Vegetation zone:  Plains, Foothills
Time of bloom:  July - October
Origin:  Introduced