Coefficient of Conservatism:
Coefficient of Wetness:
R. W. Smith
A European weed, along roadsides and railroads; in fields, gravel pits, alleys, and disturbed sites; gardens and nurseries; sometimes in moist ground. During the decade 1884–1894, collected in six counties across the southern Lower Peninsula; not in the Upper Peninsula until 1933 and still very local there.
The stiff prickles on the midrib are unique among our species of Lactuca (though some others may have hairy midribs) and will also distinguish this species from any species of Sonchus (e.g., S. asper), which may have prickly margins but smooth midribs. Lactuca biennis may have a few bristles on the midrib beneath.