Scientific name: Potamogeton praelongus Wulfen
Common name: Long-stalked Pondweed
Description
Habit: Aquatic perennials. Hybrids are rather frequent in this genus.
Leaves: Leaves mostly alternate, some opposite, submerged, subtending inflorescences, all with membranous sheath or stipules; submerged leaves oblong, with an obtuse, hooded tip, stalkless and slightly clasping the stem, 25-40mm wide; stipules large and conspicuous, more or less fibrous-persistent, up to 6cm long.
Flowers: In spikes or heads; spike rather lax, 35-50mm long; peduncle at least twice as long, not swollen at the tip; usually borne above the water-surface; perianth of 4 free, greenish segments; carpels usually 4, free; stamens 4, anthers stalkless, attached to the base of the adjoining perianth-segment.
Fruits: Drupes or achenes, 1 or more present, 4-5.5mm, with a sharp dorsal keel, dark green, with thick pericarp, soft on outside but with bony inner layer.
Habitat: Lakes and rivers, often in fairly deep water.
Distribution: Rather rare.
Native status: Native
Of conservation interest: No