Potamogetonaceae (pondweeds) A cosmopolitan family of aquatic herbs, found mostly in fresh water, that have submerged and translucent or sometimes leathery and floating leaves. The leaves may be narrow and linear, or elliptical. The inconspicuous flowers are borne in axillary or terminal spikes, are pollinated by water or wind, and have 4 sepals, 4 stamens, and 4 free carpels, each producing a fruit that is a nutlet. The family contains 2 genera, Potamogeton (about 90 species) and Groenlandia (1 species).

pondweed Any of numerous species of a family of aquatic, perennial flowering plants of the genus Potamogeton, found mostly in temperate regions in freshwater lakes, but also in brackish and salt water. Most pondweeds have spike-like flowers that stick out of the water, and submerged or floating leaves. Family Potamogetonaceae.