Calamus flagellum var. furvifurfuraceus S. J. Pei & San Y. Chen; C. flagellum var. karinensis Beccari; C. karinensis (Beccari) S. J. Pei & San Y. Chen; C. polygamus Roxburgh; Palmijuncus flagellum (Griffith ex Martius) Kuntze; P. polygamus (Roxburgh) Kuntze.

Stems clustered, climbing, to 30 m, 4.5-5 cm in diam. Leaf sheaths greenish yellow with dark brown hairs, with densely arranged, black, brownish, or yellowish, flattened spines to 5.5(-10 at sheath apices) cm, interspersed with shorter spines; ocreas fibrous, soon falling; knees inconspicuous; flagella to 7 m; rachis to 3 m with 27-35 linear-lanceolate pinnae per side, these regularly or sometimes irregularly arranged; middle pinnae 60-70 cm, 3.5-4.5 cm wide at mid-point, adaxial and abaxial veins and margins bristly; cirri absent. Inflorescences to 7 m, flagellate; inflorescence bracts tubular, tattering at apices. Fruits yellowish or brownish, ovoid, 2.7-3 × 1.8-2.2 cm, scales grooved.

The hearts are eaten.

Lowland or montane rain forests; below 1500 m. Guangxi, Xizang, Yunnan [Bangladesh, Bhutan, India, Laos, Myanmar, Nepal, Thailand, Vietnam].