Lactuca serriola is an annual or biennial herb, 0.30-1.5 m tall, from a leafy rosette, flowering stem often prickly below, sap milky.
Leaves all basal at first, stem leaves alternate, 5-25 cm long narrow, lobed or unlobed, spiny toothed, midrib prickly below, twisted at base, clasping stem, pale dull blue-green, midrib whitish, upper leaves very reduced.
Flowers pale yellow, all rays, 18-24 per head, heads 0.8-1 cm wide (Uva et al. 1997), bracteate base ca 1.2 cm tall in fruit; blooms and fruits July-Sept. Mostly self-pollinated (Weaver and Downs 2003).
Fruit dry, 1-seeded achenes, flat, several ribbed, gray with white plume attached to achene by a filament-like stalk, mostly wind dispersed; seeds live in seed bank only 1-3 years; can germinate as soon as dispersed (Weaver and Downs 2003); seeds eaten by birds (Martin et al. 1951).
Wetland status: FAC-.
Frequency in NYC: Occasional.
Habitat: Open disturbed areas, roadsides, fill.
Notes: Listed as invasive in several states. Leaves eaten by Trichoplusa ni (cabbage looper) larvae which bite off leaf spines and cut veins to release latex before eating leaf. Prickly lettuce is host to a number of fungi and viruses (Weaver and Downs 2003).