Sonchus arvensis L.  
Family: Asteraceae
field sow-thistle, perennial sow-thistle
Sonchus arvensis image
Keir Morse  
Etymology: Sonchus: the Greek name for sowthistle
Plants: erect, perennial, 16"-60" tall forb with milky juice; stems hairless below the inflorescence; deep, creeping roots forming large patches
Leaves: alternate, edges prickly, lower leaves mostly pinnately-divided, upper leaves upper smaller, less divided and with heart-shaped bases clasping part way around the stem
Flowers: head 1 1/4"-2" wide with yellow ray flowers; inflorescence of several heads in open, branched clusters; blooms July-Oct.
Fruits: wrinkled, dry seed with 5 obvious ribs on each side
Habitat: disturbed sites
Conservation Status: Introduced - naturalized
Sonchus arvensis image
Emmet J. Judziewicz  
Sonchus arvensis image
Emmet J. Judziewicz  
Sonchus arvensis image
Robert W. Freckmann  
Sonchus arvensis image
Christopher Noll