All the western states (non native)
Usually up to 40 inches, sometimes more
Roadsides, fields and other disturbed areas, from near sea level to 7,500 feet
Lanceolate to oblong, up to 5 inches in length, some partly divided into large, finely-toothed lobes
Lactuca serriola originates in Europe and Asia, and has been naturalized across most of the US. Stems are thick, erect and hairless, colored light brown to reddish brown. Large, grey-green leaves grow along the middle portion; those towards the top are generally undivided, while those lower down are deeply lobed. All leaves have finely toothed margins, wide, white midveins (prickly underneath) and intricately-branched side veins. Leaf bases are clasping, and heart-shaped.
The inflorescence is a narrow, elongated cluster. Flowerheads are formed of between 12 and 20 pale yellow ray florets, which have four notches at the tip. Phyllaries are relatively broad, green or reddish in color and triangular (at the base) to lanceolate (at the top) in shape. They stay pressed against the involucre during flowering but tend to bend outwards at the fruiting stage. Flowerheads are about half an inch in diameter.