Lactuca canadensis L.
Canada Wild Lettuce
Family - Asteraceae
Stem - Erect, to 2 m, usually glabrous, often purple mottled. Latex tan or pale orange.
Leaves - Extremely variable. Usually abundant on stem. Typically lanceolate to ovate, entire or pinnately lobed, often auriculate, sessile.
Leaves, abaxial view.
Inflorescence - Highly branched, open panicles with numerous heads.
Involucre - 8-10 mm long, cylindrical or urn-shaped, glabrous.
Flowers - Ligulate florets 17-22, orange or tan-orange in color, with 4-7 mm pappus bristles.
Fruits - 3-4 mm long, flattened and winged, nearly black, with beak shorter to same length as body of achene.
Flowering - July - September.
Habitat - Prairies, forest openings, sand prairies, streambanks, pastures, etc.
Origin - Native to North America.
This commonly encountered lettuce can be quite variable in appearance. The plant can be differentiated from other common lettuces by the presence of tan or orange latex; however, this character must be used in conjunction with other attibutes, since other species (e.g. L. hirsuta) also contain tan sap. Other key attributes include the dirty orange color of the flowering heads and a conspicuously leafy stem, though these characters are also variable.
Photographs taken at Faust County Park, St. Louis County, MO, 11-22-2010, near Dutzow, Warren County, MO, 8-6-2015, and at Sand Prairie Conservation Area, Scott County, MO, 8-12-2015 (SRTurner).