Scientific name: Zannichellia palustris L.
Common name: Horned Pondweed
Description
Habit: Aquatic rhizomatous annuals or perennials rooted in substratum; stems elongated, slender, submerged, hairless.
Leaves: Opposite, or in whorls of 3, entire, sessile, acute, narrow-linear, apex acute to obtuse, 2-7cm x 2mm (usually narrower), 1(-3) veined; sheaths free from the leaf-base, stipuliform, tubular when young.
Flowers: Monoecious, axillary, solitary or in pairs; male flowers without a perianth, the peduncle simulating a filament; stamens 1-2; anthers 2-thecous; female flowers with a cupular perianth; carpels 1-9 (usually 4), stigmas peltate, with an irregularly crenate margin, styles simple.
Fruits: Fruitlets 3-6mm (including style), sometimes subsessile, laterally compressed, often curved, crenate-dentate, beaked.
Habitat: Ponds, ditches and lakes, in fresh or brackish water.
Distribution: Locally frequent near the coast, rare inland.
Native status: Native.
Of conservation interest: No