131865 OPPOSITE-LEAVED PONDWEED Groenlandia densa (Potamogetonaceae) Aquatic. Submerged, freshwater perennial of ponds and ditches, as well as streams with a moderate flow. FLOWERS are small, petal-less and greenish; borne in small, submerged clusters (May-Sep). FRUITS comprise small clusters of achenes. LEAVES are narrow-ovate, pointed-tipped and borne in opposite pairs. STATUS-Locally common only in S.