Common Duckweed - Lemna minor

Fronds pale green, rounded to oval, 1.5 mm, opaque, floating, flat, 3 veined. Linked by an inconspicuous stalk or separate and with a single root.

Other Lemna, especially L minuta, which has only one vein on the frond

Only use well-grown material in summer.  Ovate (widest near middle), no red pigmentation, 3 or more obscure veins on underside

Photo of summer leaf frond underside, with veins

Lakes, ponds, ditches and backwaters - even in cattle troughs.

May to July.

Perennial.

Common throughout Britain except the north of Scotland.

Common in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 405 of the 617 tetrads. 

It is probably over-recorded instead of L minuta.