Algae-leaved pondweed is a submergent aquatic forb with elongate peduncles elongate, most 5-25cm, a head-shaped spike with few flowers, 5-12mm. Its achenes are swollen, broadly obovoid, 2-3mm, with a sharp dorsal keel flanked by a pair or more obscure ones. It has numerous very slender, 1-veined leaves, all submersed very soft and delicate, flat, 2-5cm long by 0.25mm wide, tapering to a hair-like tip. Stipular sheaths are axillary, obtuse, 1-5cm.
pondweed is a submergent aquatic forb