Submerged herb, with branches flattened, up to at least 4 m long. Leaf sheath free, up to 0.5 cm long; ligule absent. Leaves sessile; lamina narrowly ovate to narrowly oblong, 2.5–5(–7) cm long, 0.5–1(–1.5) cm wide, thin and translucent; base obtuse to rounded; margin serrulate, undulate to strongly crisped; apex obtuse; (3 or)5 principal longitudinal veins, without fine secondary longitudinal veins; leaves sometimes considerably reduced to form scales of the 'winter buds'; winter buds clustered on distal ends of branches. Inflorescence 3–14-flowered. Infructescence 0.8–1.5(–2) cm long. Fruiting carpels 5–7 mm long (including distal point), basally with a ± crenulate dorsal keel and with smooth to strongly tuberculate sides, distally with a conspicuous, thick, tapered, straight or ±curved point c. 2 mm long. Flowers and fruits Nov.–May.
MuM, GleP, VVP, VRiv, MSB, RobP, MuF, GipP, OtP, WaP, Gold, CVU, GGr, DunT, NIS, EGL, EGU, WPro, HSF, HNF, OtR, Strz, MonT. All States. Europe, Asia, eastern and southern Africa, introduced in North America and New Zealand. Occurs in still to strongly flowing fresh water in lagoons, creeks and rivers, on muddy, sandy, or stony substrates.
Aston (1973) points out that care should be exercised in distinguishing new, vegetative growth of this species from Potamogeton ochreatus; the venation should always be examined. The leaves of P. ochreatus always have numerous fine longitudinal veins, whereas these fine secondary veins are absent in P. crispus. Very young material of P. crispus usually lack leaf undulations and have linear leaves with minute teeth which are only visible under higher magnification.
