Perennials, 30–150 cm tall. Rhizomes stout, 3–5 mm in diam., long-creeping, with non-swollen nodes. Cataphylls 1–3, stramineous to pink; basal leaves absent. Cauline leaves 2, 50–70 (–100) cm long, terete, unitubular, perfectly septate; tip subacute; proximal leaves usually overtopping inflorescence; distal leaves usually inflated bladeless sheaths, occasionally absent or with well developed blades; auricles 0.3–0.5 mm long, rounded, scarious; submersed plants with long capillary leaves borne in fascicles on the rhizomes. Lower bract an inflated sheath with or without a blade; blade leaf-like, green, terete, 2 cm long, shorter than the inflorescence; other bracts herbaceous, lanceolate, 4–13 mm long. Inflorescence decompound, of 20–100 heads, 4–15 cm tall, with erect to ascending branches; heads semiglobose to turbinate, (3–) 5–13 (–25)-flowered, 6–8 mm in diam. Tepals subequal, lanceolate, stramineous or reddish, acuminate to aristate, 2.3–3.2 (–4) mm long (inner often slightly longer). Stamens 6, not exserted; anthers 0.7–1 mm long; filaments 0.6–0.7 mm long; style 0.1–0.2 mm long (difficult to distinguish from young rostrum); stigmas 1–1.2 mm long. Capsules unilocular, from ovoid base gradually tapering into thin conical c. 0.8 mm rostrum, stramineous to pale brown, shining, 2.3–3.3 mm long, ±equalling perianth. Seeds ovoid, brown, 0.5–0.6 × 0.2–0.3 mm, reticulate; appendages absent.