Description from Flora of China
Rhizome with rather thick, stiff stolons. Culms 30-40 cm tall, triquetrous, smooth, scabrid on upper part, clothed with red-brown and bladeless sheaths at base. Leaves slightly longer than or equaling culm, blades 2-3 mm wide, flat, stiff, scabrous on margins, rather long sheathed. Involucral bracts leafy, lowermost involucral bract longer than inflorescence, upper involucral bracts shorter than inflorescence, nearly not sheathed. Spikes 3 or 4; terminal 1 or 2 spikes male, approximate, narrowly cylindric or lanceolate, 1.2-2.5 cm, sessile; remaining spikes female, remote, cylindric, 2.5-3.5 × 0.5-0.6 cm, densely many flowered, lowermost one shortly pedunculate, upper ones nearly sessile. Female glumes brown-yellow, ovate, ca. 3 mm, membranous, 3-veined, brownish yellow between veins, apex acuminate, shortly aristate, scabrous on margins of awn. Utricles stramineous, obliquely patent, slightly longer than glume, elliptic or broadly ovate, subplano-convex, slightly inflated, 3.5-4 mm, leathery, glabrous, slightly shiny, indistinctly veined, base subrounded or broadly cuneate, apex abruptly narrowed to a short beak, orifice shortly 2-toothed, teeth straight. Nutlets rather loosely enveloped, subobovate, trigonous, ca. 2 mm, base stipitate; style rather long, base not thickened, slightly recurved; stigmas 3, rather short. Fl. and fr. May-Jul.
Based on its original description, Carex purpureovaginalis Q. S. Wang (J. Wuhan Bot. Res. 5: 343. 1987, "purplevaginalis") is very difficult to distinguish from C. tangiana. We have not seen the type specimen and so cannot make a provisional determination here.
● Damp places in valleys, ditch sides, roadsides; 500-1000 m. Gansu, Hebei, Heilongjiang, Henan, Jilin, Liaoning, Shaanxi, Shanxi.