E-Flora BC: Electronic Atlas of the Flora of British Columbia

Spirodela polyrhiza (L.) Schleiden, orth. var.
great duckweed

Introduction to Vascular Plants

© Jamie Fenneman  Email the photographer   (Photo ID #11427)

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Distribution of Spirodela polyrhiza
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Species Information

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Fronds annual, free-floating, round to egg-shaped, (3) 5-10 mm long, purplish beneath, stalked, in single or small groups, 5- to 11-nerved, with 5 to 15 rootlets.
Usually 3 per pouch, 2 male, 1 female, enclosed in 2 lateral budding pouches sheathed by a minute membrane.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Ponds and slow-moving streams in the lowland, steppe and montane zones; frequent in SW and SC BC, infrequent elsewhere except absent on N Vancouver Island, the Queen Charlotte Islands and NW BC; circumpolar, E to PQ and NS and S to FL, MS, TX, NM, AZ, CA and MX; Eurasia, S America.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Spirodela polyrhiza

The table below shows the species-specific information calculated from
original data (BEC database) provided by the BC Ministry of Forests and Range.
(Updated August, 2013)

Site Information
Value / Class




Elevation (metres) 420 589 758
Slope Gradient (%) 0 0 0
Aspect (degrees)
[0 - N; 90 - E; 180 - S; 270 - W]
Soil Moisture Regime (SMR)
[0 - very xeric; 4 - mesic;
8 - hydric]
7 7 8
Modal Nutrient Regime
Number of field plots
 species was recorded in:
Modal BEC Zone Class
All BEC Zones (# of stations/zone) species was recorded in: BG(1), IDF(1)


The climate type for this species, as reported in the: "British Columbia plant species codes and selected attributes. Version 6 Database" (Meidinger et al. 2008), is not evaluated, unknown or variable.

Synonyms and Alternate Names

Lemna polyrrhiza L.
Spirodela polyrhiza
Spirodela polyrrhiza var. masonii Daubs

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References