Perennials, 30–60 cm tall, robust, loosely caespitose; rhizomes long, creeping, covered with brownish scales, stout, 2–3 mm thick; stolons present. Stem erect, terete, 2–5 mm thick. Cataphylls 1–2, purplish-brown; leaves flat, grass-like; basal leaves 1–2, shorter than upper cauline leaves, 3–10 cm long including sheath, 1–1.5 cm wide; sheath 2–5 cm long; cauline leaves 2–4, 10–30 cm long, 1–2 cm wide; leaf margin broad-membranous, often ±serrulate; auricles obliquely ±absent. Lower bract leaf-like, exceeding inflorescence, 10–15 cm long, 3–6 mm wide, flat, grass-green. Inflorescence anthelate, 3–10 cm long, with 2–4 main branches and 1 to several secondary ones, of 3–8 subglobose 5–20-flowered heads 1–2 cm wide, subtended by several bracts, yellowish white; bracts of heads lanceolate to ovate-lanceolate, 3–15 mm long, 1.5–4 mm wide; sheath-like bract on peduncle membranous, lanceolate, 0.5–0.8 cm long. Flowers 6–8 mm long, 2–3 mm wide; pedicels 1.5–6.0 mm long. Tepals lanceolate; inner tepals 3.5–5.0 mm long, 0.8–2.5 mm wide; outer tepals 3.0–4.0 mm long, 0.8–2.4 mm wide, yellowish white. Stamens 6, ±not exserted, 2.6–3.3 mm long; anthers slightly longer than filaments, linear-elliptic, 1.4–1.8 mm long; filaments 1.2–1.5 mm long; style 1.3–1.5 mm long; stigmas 0.5–0.7 mm long; ovary ovoid-trigonous, 1.6–1.9 mm long, 0.8–1.0 mm wide. Capsule unilocular, oblong-ovoid, subtrigonous, acute, subabruptly contracted in a short mucro, 4.2–6.5 (–8) mm long, pale castaneous-brown, usually exceeding perianth. Seeds ovoid, 0.6–0.8 × 0.3–0.4 mm, 2.4–3.0 mm long including two appendages c. 0.8–1.1 mm long; outer seed-coat very loose.
Confined to Yunnan, SW China. 36: CHC.
36. CHINA: Yunnan, Dali Shi, Diancang Shan, Zhonghe Temple – Ximatang, 3200 m, S.K.Wu & al. 103138 (KUN, TI); Yunnan, Lushui Xian, Pianma – Pianma Pass – Lushui, 3200 m, S.K.Wu & al. 103173 (KUN, TI); Dali, Tsang Shan, Longquan Peak, 3460 m, 15 Oct 1990, [anonymous: CLD-90] 1343 (K); Shweli Salwin divide, G.Forrest 9026 (K, S); W Yunnan, Yü Hsien, Kung Hsien, McLaren's collectors L90A (K); Yunnan, H.T.Tsai 58016 (K); Yunnan, Tali Range, 2250 m, G.Forrest 28009 (S).
Banks of streams, grasslands, thickets and slopes in Abies forests, above 2000 m.
Recently, a new species of the group of J. crassistylus and J. amplifolius was discovered in the Xiaojin region, Sichuan, China. F.Miyamoto and H.Ohba call it Juncus hamulus (the description submitted to J. Jap. Bot.); it is characterized by brown tepals with a hook-like appendage near the tip, long stigmas, long-creeping rhizomes, and leaves 1.5–7 mm wide.