Perennial plants up to 2–2.5 m long. Rhizomes up to 0.5 m long, (1.7) 2.5–6 (7.5) mm in diameter. Stems (0.7) 1–3 (4.2) mm in diameter, strong, rather sparsely branched, branches more or less parallel to the main stem. The stem in 1–3 basal nodes with dark brown to black scales (1.5) 2–6 (7.8) cm long, tightly embracing the stem or with their upper part free, or possibly bearing rudimentary leaves. Leaves always submerged, linear, green to dark green (brownish green when near the surface), those of mature shoots 15–25 (30) cm long and (0.9) 1.5–2.5 mm wide, the lower leaves and those of overwintering shoots (5) 7–15 cm long, 3–4.6 mm wide, stiff, truncate, rounded, subretuse, usually asymmetrical at the apex, entire, with 1–2 inconspicuous lateral veins and several air channels on each lateral side. Sheaths dark green, sometimes with a tinge of grey, with hyaline brownish margins, tubular in 2–10 (20) mm above the node, or some tubular and the others open (tubular sheaths are often recognizable in the upper part of plant only), (3.5) 5–10 cm long, 2–6 (7.5) mm wide, solid, with prominent veins, the lower ones significantly enlarged, embracing 2–3 branches; ligules 3–15 (20) mm long, hyaline, rounded or truncate at the apex. Inflorescences 12–17-flowered, 4–8 cm long, 3–4.5 mm wide, with 6–9 equally spaced whorls of (1) 2 flowers; peduncles 5–15 cm long, 0.7–0.9 mm wide, rigid, flexuous. Stamens small, pollen grains mostly sterile, misshapen, not filled; carpels 4, stigmas sessile. Fruits not developing. Vegetative reproduction by fragments of rhizomes and stems, and by small plantlets appearing on short axillary stolons; the tubers characteristic to the parental species are not found.