is a biennial or short-lived perennial from a taproot to 75 cm long, flowering stem to 2 m tall, prickly especially above, pithy or hollow, branching opposite, producing an overwintering rosette the first year, flowering stalk forms only when rosette becomes about 30 cm in diameter (Werner 1975).
Leaves opposite, prickly on midrib below, basal leaves inversely lance-shaped, upper surface with small spines from papillae, margins crenate, stem leaves lanceolate, fused at base across stem, to 30 cm long.
Flowers pink-purple, 4-parted, to 1.5 cm long, corolla tubular; numerous embedded in floral bracts tipped by an awn longer than the individual flower; inflorescence of terminal, cylindrical heads to 10 cm long, above linear, up-curved, elongate, unequal bracts, with spiny midribs; blooms July-Sept. Visited by bumblebees and small bees, self pollination produces few seeds.
Fruit dry, an achene to 0.5 cm, 4-angled; seeds fall near parent plant, often dispersed by water (Werner 1975); Seeds eaten by ants.
Wetland status: UPL.
Frequency in NYC: Very infrequent.
Habitat: Open, disturbed sites. Prefers moist soil, tolerates spring flooding.
Notes: Stems and flower heads becoming woody and persistent for as long as 3 years after seed set. Plants in partial shade attacked by an unidentified stem borer. Host to several fungi including: the leaf spots fungi Cercospora elongata and Mycosphaerella asterinoides; and the downy mildew Peronospora dipsaci, (Werner 1975).