Photos: Co. Wexford
Slightly translucent, +/- symmetrical plants, 0.8-4mm long with a single vein (can be difficult to see). Rarely flowers, flowers minute, solitary, easily overlooked.
Introduced from America, first recorded in Britain and Ireland in 1977. Spreading but easily overlooked in still or slow-moving ponds, ditches, rivers.
Very similar: Lesser / Common Duckweed, L. minor; larger, 3-5 veins.
Above: Lesser Duckweed, L. minor with Least Duckweed, L. minuta. 2010