Greater Duckweed - Spirodela polyrhiza

Description

This is an aquatic plant, usually growing in dense colonies, forming a mat on the water surface. Each plant is a smooth, round, flat shiny green disc on top and often purplish underneath. It may measure 4 to 10 mm across and produces several minute roots (at least two, unlike Common Duckweed).

Similar Species

Lemna species

Identification difficulty
ID guidance

Many roots, large fronds, reddish underside and turns red in autumn, multiple veins

Recording advice

The County Recorder has asked for a specimen of this plant to be retained for verification

 

Habitat

Mainly found in still water such as ponds.

When to see it

Spring and summer, dying back in the autumn.

Life History

Perennial.

UK Status

British records are mainly concentrated in central and southern England.

VC55 Status

Scarce in Leicestershire and Rutland. In the 1979 Flora survey of Leicestershire it was found in 7 of the 617 tetrads. 

It is now listed in the VC55 Rare Plant Register (Jeeves 2011)

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Leicestershire & Rutland Map

MAP KEY:

Yellow squares = NBN records (all known data)
Coloured circles = NatureSpot records: 2020+ | 2015-2019 | pre-2015

UK Map