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

You must attach images that show sufficient detail for the plant to be identified.

 

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

It is near scarce in Leicestershire and Rutland. In the Flora of Leicestershire (Primavesi and Evans 1988) it was found in 7 of the 617 tetrads. 

It was on the 2011 VC55 Rare Plant Register (Jeeves, 2011) but does not meet the criteria for the current RPR (Hall and Woodward, 2022)

Leicestershire & Rutland Map

MAP KEY:

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

UK Map

Species profile

Common names
Great Duckweed, Greater Duckweed
Species group:
Wildflowers
Kingdom:
Plantae
Order:
Alismatales
Family:
Araceae
Records on NatureSpot:
9
First record:
06/09/2012 (Nicholls, David)
Last record:
27/09/2022 (Nicholls, David)

Total records by month

% of records within its species group

10km squares with records

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