Herbs, perennial, often caespitose from a stout and woody rootstock with rhizomes. Stems erect, to 1 m tall, 4-angled, glabrous to puberulent at least at nodes, smooth. Leaves in whorls of 6-12, sessile; blade drying papery, linear-oblanceolate to linear, 20-28 × 1-3 mm, glabrous, more rarely ± hairy, base acute to straight, margin shortly to strongly revolute and usually antrorsely aculeolate, apex acute and mucronate; vein 1. Inflorescences narrowly paniculate with main stems and short lateral and terminal, few- to several- or many-flowered, rather congested cymes; peduncles glabrous, smooth; pedicels 0.5-3 mm, subtended by leaflike bracts. Ovary subglobose to obovoid, 0.5-0.8 mm, smooth, glabrous or ± hispidulous with straight hairs. Corolla yellow, rotate, ca. 3 mm in diam., glabrous, lobed for 3/4 or more; lobes 4(or 5), lanceolate-oblong, acute to acuminate. Mericarps ellipsoid to obovoid, ca. 1.5 × 1 mm, glabrous or ± hispidulous with straight trichomes. Fl. Jul-Aug, fr. Aug-Sep.