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

Potamogeton illinoensis Morong
Illinois pondweed
Potamogetonaceae (Horned pondweed family)

Introduction to Vascular Plants
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Distribution of Potamogeton illinoensis
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Species Information

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Perennial, aquatic herb from strong rhizomes; stems up to 200 cm long, usually branched.
Submersed leaves elliptical to widely lanceolate, thin, flat, intense yellow-green, 8-20 cm long, 2-5 cm wide, with 7 to 19 veins, the tips sharp-pointed, tapering into long stalks at the bases, the stalks less than 2 cm long, the stipules 2.5-8 cm long; floating leaves often absent, if present elliptical, 5-20 cm long, 2-7 cm wide, leathery, long-stalked, the tips pointed, tapering at the bases.
Inflorescence spikelike, the spikes with 8 to 15 whorls of flowers, the stalks thick, inflated.
Achenes, widely egg-shaped or almost globe-shaped, 2.5-3.6 mm long, 2.1-3 mm wide, the beaks widely triangular, the keels wide.
Stem anatomical characters Interlacunar bundles strongly developed in 1 circle, often with few additional bundles in neighbouring circles, subepidermal bundles usually absent, pseudohypodermis absent or 1 cell thick, endodermis of U-cells.

Source: The Illustrated Flora of British Columbia

Habitat / Range

Lakes and slowly flowing streams in the steppe zone; infrequent in S BC east of Coast-Cascade Mountains; N to NT, disjunct E from MB to PQ and NS and S to ME, MA, PA, NC, FL, MS, TX, NM, AZ and CA.

Source: The Illustrated Flora of British Columbia


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 angustifolius Bercht. & C. Presl
Potamogeton heterophyllus Schreb.
Potamogeton lucens auct. non L.

Taxonomic and Nomenclatural Links

Additional Photo Sources

General References