Barbed rattlesnakeroot

Nabalus fraseri de Candolle var. barbatus Torrey & A. Gray, Fl. N. Amer. 2: 481. 1843; Prenanthes serpentaria Pursh var. barbata (Torrey & A. Gray) A. Gray

Plants 50–150 cm; taproots thickened, tuberous, with lateral side roots. Stems erect, purplish, glabrous proximally, finely tomentulose or setose distally. Leaves: proximal withered by flowering; petiolate (petioles 2–3 cm, winged; blades ± elliptic, 4–10 × 1–4 cm, coriaceous, bases narrowed (not hastate), margins coarsely and irregularly dentate or serrate (unlobed), apices acute, faces glabrous or papillose-hispid; mid cauline cuneate or sessile and clasping; distal sessile and reduced. Heads (15–50) in (much-branched) paniculiform or thyrsiform arrays (nodding). Calyculi of 7–11, dark green to purple, triangular to lance-ovate bractlets 2–5 mm, hispid or setose along midveins. Involucres cylindric to campanulate, 12–16 × 4–6 mm. Phyllaries 6–8, usually purple or lavender, subulate to lanceolate, 11–14 mm, margins scarious, coarsely hispid or setose along midveins. Florets 10–15; corollas white to yellowish white, 13–16 mm. Cypselae tan, subcylindric, subterete to 5-angled, 8–10 mm, indistinctly 8–10-ribbed; pappi yellowish white, 7–8 mm.

Flowering Aug–Oct. Sandy oak-hickory-pine woods, savannas, prairies, pine barrens; 10–100 m; Ala., Ark., Ga., Ky., La., Okla., Tenn., Tex.

Prenanthes barbata is identified by its erect habit, irregularly dentate leaves, heads with 6–8 purple phyllaries, coarsely setose calyculi and phyllaries, and white to yellowish white corollas.