Lactuca biennis is an annual or biennial herb, (NYS S1, E) large, 60 cm to 3 m tall, sap milky.
Leaves alternate, 10-40 cm long, 4-20 cm wide, irregularly pinnately divided, base lobed, margin toothed, upper leaves stalkless.
Flowers blue-white, all rays, heads with 15-34 flowers, bracteate base about 1 cm tall in fruit; heads crowded in a narrow, branched inflorescence; blooms and fruits July-Sept.
Fruit dry 1-seeded achene, seed 0.5 cm with pale brown plume; seeds eaten by birds, plants eaten by deer (Martin et al. 1951).
Wetland status: FACU.
Frequency in NYC: Very infrequent.
Habitat: Moist open areas, gaps in open woods.