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

Potamogeton gramineus L.
grass-leaved pondweed (variableleaf pondweed)
Potamogetonaceae (Horned pondweed family)

Introduction to Vascular Plants

© Jamie Fenneman  Email the photographer   (Photo ID #14605)

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Distribution of Potamogeton gramineus
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Species Information

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Perennial, aquatic or semi-terrestrial herb from strong rhizomes; stems up to 150 cm long, freely branched, nearly circular in cross-section, tapered.
Submersed leaves narrowly lanceolate, thin, flat, green, 2-7 cm long, 0.5-2.5 cm wide, unstalked, not clasping the stem, the tips rounded or pointed, the stipules 0.5-3 cm long; floating leaves markedly different from the submersed ones, lanceolate to elliptical, thick and leathery, 2-10 cm long, 1-4 cm wide, long-stalked, the tips pointed, tapering at the bases.
Inflorescence spikelike, the spikes 1-2.5 cm long, with 5 to 10 whorls of flowers, the stalks thin.
Achenes, almost globe-shaped, 1.7-2.5 mm long, 1.6-2 mm wide, the beaks short, the keels sharp and prominent.
Stem anatomical characters Interlacunar bundles present in 1 circle, subepidermal bundles present or absent, pseudoepidermis absent or 1 cell thick, endodermis of U-cells. A highly variable species with several varieties described in N America based on stem branching and size of submersed leaves (e.g. var. maximus Morong ex A. Benn., var. myriophyllus Robbins). Their taxonomic recognition is questionable. Potamogeton gramineus hybridizes with P. natans and without examining stem anatomical characters, this hybrid (P. sparganiifolius Laest. ex Fries) can easily be misidentified as P. nodosus.

Source: The Illustrated Flora of British Columbia

USDA Species Characteristics

Flower Colour:
Blooming Period:
Late Spring
Fruit/Seed characteristics:
Colour: Brown
Present over the Summer
Source:  The USDA

Habitat / Range

Lakes, lake margins, ponds in peat bogs, ditches and slowly flowing streams and rivers in all but the alpine zone; frequent throughout BC; circumpolar, N to AK, YT and NT, E to NF and S to ME, MA, PA, WV, OH, IN, IL, IA, NM, AZ and CA; Eurasia.

Source: The Illustrated Flora of British Columbia


Ecological Framework for Potamogeton gramineus

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) 110 833 1230
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]
6 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), BWBS(1), CDF(2), CWH(14), ICH(5), IDF(17), SBPS(6), SBS(2)


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

Potamogeton gramineus
Potamogeton gramineus
Potamogeton gramineus var. graminifolius Fr.
Potamogeton gramineus var. maximus Morong
Potamogeton gramineus var. myriophyllus J.W. Robbins
Potamogeton gramineus var. typicus Ogden

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References