Roadless Areas
Home/Species/ Common Water-flaxseed

Spirodela polyrhiza

(L.) Schleiden.

Common Water-flaxseed

G5Secure Found in 5 roadless areas NatureServe Explorer →
G5SecureGlobal Rank
Least concernIUCN
UnknownThreat Impact
Identity
Unique IDELEMENT_GLOBAL.2.145456
Element CodePMLEM02010
Record TypeSPECIES
ClassificationSpecies
Classification StatusStandard
Name CategoryVascular Plant
IUCNLeast concern
Endemicoccurs (regularly, as a native taxon) in multiple nations
KingdomPlantae
PhylumAnthophyta
ClassMonocotyledoneae
OrderArales
FamilyAraceae
GenusSpirodela
Synonyms
Lemna polyrhizaL.Spirodela polyrrhiza(L.) Schleid.
Other Common Names
common duckmeat (EN) Common Duckmeat (EN) Great Duckweed (EN) Spirodèle polyrhize (FR)
Concept Reference
Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
Taxonomic Comments
"The spelling of the epithet is correctly 'polyrhiza', matching Linnaeus's basionym; there is no basis in the Code to change the spelling to 'polyrrhiza'" (Weakley 2020).
Conservation Status
Rank Method Rank calculation - Biotics v2
Review Date2025-05-12
Change Date1984-09-06
Edition Date2025-05-12
Edition AuthorsN. Ventrella (2025)
Threat ImpactUnknown
Range Extent>2,500,000 square km (greater than 1,000,000 square miles)
Number of Occurrences> 300
Rank Reasons
Spirodela polyrhiza is an aquatic monocot occurring in a wide variety of still or slow-moving freshwater environments worldwide. In North America, it is found from British Columbia east to Quebec and Nova Scotia and throughout the entire United States. There are over thousands of estimated occurrences of this taxon, which are potentially threatened by water diversion, alteration of hydrology, erosion, pollution, invasive species, and other threats in some places. Little is known about threats or trends, but with a large range extent, high number of occurrences, abundant habitat, broad habitat preferences, and no obvious intrinsic vulnerabilities, Spirodela polyrhiza is considered secure.
Range Extent Comments
Spirodela polyrhiza occurs nearly worldwide as a native species (POWO 2025). In North America, it is found from British Columbia east to Quebec and Nova Scotia and throughout the entire United States (FNA 2000). Range extent was estimated using herbarium specimens and photo-based observations documented between 1994 and 2025 (GBIF 2025, iNaturalist 2025, RARECAT 2025, SEINet 2025).
Occurrences Comments
By applying a 1 km separation distance to herbarium records and photo-based observations documented between 1994 and 2025, there are estimated to be thousands of occurrences rangewide (GBIF 2025, iNaturalist 2025, RARECAT 2025, SEINet 2025).
Threat Impact Comments
Threats to Spirodela polyrhiza are not widely documented but likely include water diversion, alteration of hydrology, erosion, pollution, invasive species, and other threats in some places, though there is insufficient data, including anecdotal accounts, to understand scope and severity of threats for this species.
Ecology & Habitat

Habitat

Spirodela polyrhiza occurs in a wide variety of still or slow-moving freshwater environments (e.g., ponds, ditches, marshes, backwaters) up to 2792 m in elevation (Les 2020). It prefers full sunlight, and alkaline, hard, eutrophic, quiet waters with substrates like gravel or sand.

Reproduction

Fronds and turions disperse abiotically (via water, wind) and by animals (e.g., ducks, muskrats) (Les 2020).
Palustrine Habitats
HERBACEOUS WETLANDFORESTED WETLAND
Other Nations (2)
United StatesN5
ProvinceRankNative
OregonSNRYes
WyomingS2Yes
North DakotaSNRYes
MississippiSNRYes
AlabamaSNRYes
District of ColumbiaSNRYes
Rhode IslandSNRYes
MassachusettsSNRYes
OklahomaSNRYes
MissouriSNRYes
PennsylvaniaS5Yes
UtahS1Yes
IllinoisS5Yes
KentuckyS5Yes
TennesseeSNRYes
DelawareS5Yes
ConnecticutSNRYes
South CarolinaSNRYes
VermontS5Yes
VirginiaS4Yes
New HampshireSNRYes
North CarolinaS4Yes
MichiganSNRYes
West VirginiaS3Yes
NevadaSNRYes
IdahoSNRYes
New MexicoSNRYes
LouisianaSNRYes
MarylandSNRYes
ArkansasSNRYes
GeorgiaSNRYes
New YorkS5Yes
MinnesotaSNRYes
WashingtonSNRYes
IowaS4Yes
HawaiiSNRYes
FloridaSNRYes
NebraskaSNRYes
KansasS5Yes
IndianaSNRYes
TexasSNRYes
MontanaSNRYes
South DakotaSNRYes
ColoradoS3Yes
ArizonaSNRYes
MaineSNRYes
OhioSNRYes
New JerseyS4Yes
CaliforniaSNRYes
WisconsinSNRYes
CanadaN5
ProvinceRankNative
OntarioS5Yes
ManitobaS3Yes
Nova ScotiaS4Yes
SaskatchewanS4Yes
New BrunswickS4Yes
British ColumbiaS5Yes
Prince Edward IslandS4Yes
QuebecS4Yes
AlbertaS3Yes
Threat Assessments
ThreatScopeSeverityTiming
Unknown/undetermined———

—

Plant Characteristics
DurationPERENNIAL
Economic Value (Genus)No
Roadless Areas (5)
California (1)
AreaForestAcres
PattisonShasta-Trinity National Forest29,299
Montana (1)
AreaForestAcres
Cube Iron - SilcoxLolo National Forest36,998
Utah (1)
AreaForestAcres
WellsvilleWasatch-Cache National Forest1,717
Virginia (1)
AreaForestAcres
Seng MountainJefferson National Forest6,428
Wyoming (1)
AreaForestAcres
Teton Corridor TrailheadsBridger-Teton National Forest286
References (9)
  1. Flora of North America Editorial Committee (FNA). 2000. Flora of North America north of Mexico. Vol. 22. Magnoliophyta: Alismatidae, Arecidae, Commelinidae (in part), and Zingiberidae. Oxford Univ. Press, New York. xxiii + 352 pp.
  2. Global Biodiversity Information Facility (GBIF). 2025. Global Biodiversity Information Facility (GBIF) data portal. Online. Available: https://www.gbif.org/ (accessed 2025).
  3. iNaturalist. 2025. Online. Available: https://www.inaturalist.org (accessed 2025).
  4. Kartesz, J.T. 1994. A synonymized checklist of the vascular flora of the United States, Canada, and Greenland. 2nd edition. 2 vols. Timber Press, Portland, OR.
  5. Les, D. 2020. Aquatic Monocotyledons of North America: Ecology, Life History, and Systematics. CRC Press, Boca Raton, FL. 568 pp.
  6. NatureServe's Rapid Analysis of Rarity and Endangerment Conservation Assessment Tool (RARECAT). 2024. Version: 1.1.1 (released Oct 01, 2024).
  7. Plants of the World Online (POWO). 2025. Plants of the World Online. Facilitated by the Royal Botanic Gardens, Kew. Online. Available: https://powo.science.kew.org/ (accessed 2025).
  8. Southwest Environmental Information Network (SEINet). 2025. Collections Databases. Online. Available: https://swbiodiversity.org/seinet/collections/index.php (accessed 2025).
  9. Weakley, A.S. 2020. Flora of the Southeastern United States. 20 October 2020 Edition. University of North Carolina Herbarium (NCU), North Carolina Botanical Garden, University of North Carolina at Chapel Hill.