Perennials, 60–210 cm (rhizoma-tous, forming colonies). Stems erect to ascending, striate, glabrous, gland-dotted, resinous. Leaves present at flowering; short-petiolate; blades (1- or 3-nerved, larger prominently 3-nerved) lanceolate, 50–130 × 8–30 mm, bases tapered to petioles, margins entire or finely dentate, apices acute to acuminate, faces glabrous, black gland-dotted. Heads in dense, terminal, flat-topped, corymbiform arrays. Involucres hemispheric; staminate 3.5–5 mm, pistillate 3.8–4.8(–6) mm. Phyllaries narrowly lanceolate, 2–4 mm, inner series ± equal, margins yellowish, medians green to purplish, apices acuminate, erose or ciliate, faces glabrous, gland-dotted, resinous. Staminate florets 26–40; corollas 3.5–4 mm. Pistillate florets 80–150; corollas 1.7–3 mm. Cypselae 0.6–1.5 mm, 5-nerved, glandular, hispidulous distally; pappi 2.6–4(–7) mm. 2n = 18.
