Northern Prairie Wildlife Research Center
Found in every county in North Dakota, wild blue lettuce also occurs from western Ontario to south-central Alaska south to Oklahoma and California at elevations up to 8,000 feet.
Blue lettuce is a hairless perennial with milky juice (latex) and a deep taproot. Young plants occur singly, but older individuals have multiple stems that arise from rhizomes connected to a heavy rootcrown. Plants up to 3 feet tall occur in southern areas, but North Dakota specimens are usually less than 2 feet tall. Leaves are 2-4 inches long and nearly always deeply cleft on each side. The ray flowers on the outside of the flower heads are blue to lavender or rarely white. About 10-30 flower heads form a loose cluster at the top of the plant. The reddish achenes (seeds) are about 3/16 inch long and attached to a tuft of white bristles about 1/2 inch long.
Look for blue lettuce from June through September in low, moist prairie. Most plants will be found where grazing pressure is light or moderate, rather than heavy. Many of the world's wild Lactucas are used as potherbs or in salads and a few are used medicinally, but I could find no mention of blue lettuce in this regard.
Blue lettuce is a member of the sunflower family (Asteraceae). Aster means "star" in Greek, in reference to the radial arrangement of the flowers in the heads. Lactuca is a cosmopolitan genus of about 50 species found in north- temperate regions and tropical Africa. Seven of 15 North American species are found in the Great Plains. Lactuca is the ancient name of lettuce, from lac, "milk", in allusion to the milky juice. Oblongifolia means "with oblong leaves" in botanical Latin. Blue lettuce was first described for science in 1813 by Thomas Nuttall. He visited the Mandan villages along the Missouri River in 1810-1811.