Opposite-leaved pondweed
Scientific name: Groenlandia densa (L.) Fourr. Family: Potamogetonaceae
MORPHOLOGY
Habit and size: Completely submerged aquatic plant, ranging from 30 to 50 cm in length.
Stem: Cylindrical stem, sparsely branched.
Leaves: Dense, opposite or sometimes in whorls of 3, usually ovate-lanceolate (5-12 x 15-30mm), sessile and clasping, folded, serrated along the edge, acute.
Flowers: Sparse spike (5-10 mm) on a peduncle of similar or slightly longer length, curved after flowering. Blooms from May to June.
Fruits and seeds: Achenium (poliachene) formed by achenes measuring 2.7-4 x 2-2.7 mm, obovoid.
DISTRIBUTION AND HABITAT
Present throughout Italy except Sardinia and Friuli, in stagnant or slow-moving water, from 0 to 1,000 m.
Photos: under free license from Saxifraga and Peter Meininger, Rutger Barendse



















