Page authors: Don Knoke, David Giblin
Potamogeton illinoensis
illinois pondweed

Distribution: Occurring on both sides of the Cascades crest in Washington; Northwest Territories to California, east across much of North America to the Atlantic Coast.

Habitat: Ponds and lakes, usually in rather deep, quiet water.

Flowers: May-August

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern

Pollination: Wind


Aquatic, herbaceous perennials from slender rhizomes, the stems simple to freely branched, terete, up to 2 m. long.


Leaves alternate, the submersed leaves thin, lanceolate to elliptic or oblanceolate, 10-20 cm. long and 2-4 cm. broad, sub-sessile or tapered to a short petiole, prominently 9- to 19-nerved; floating leaves, if any, rather firm, transitional to the submersed leaves; stipules 3-7 cm. long.


Flowers perfect, in compactly-flowered spikes 3-6 cm. long, on peduncles 4-12 cm. long, thicker than the stem; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.


Achenes broadly obliquely obovoid, 4 mm. long including the short beak, the dorsal keel prominent and sharp, the lateral keels also prominent.

Accepted Name:
Potamogeton illinoensis Morong
Publication: Botanical Gazette. 5: 50. 1880.

Synonyms & Misapplications:
Potamogeton lucens L., misapplied
Additional Resources:

PNW Herbaria: Specimen records of Potamogeton illinoensis in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Potamogeton illinoensis checklist entry.

OregonFlora: Potamogeton illinoensis information.

E-Flora BC: Potamogeton illinoensis atlas page.

CalPhotos: Potamogeton illinoensis photos.

USDA Plants: Potamogeton illinoensis information.

23 photographs:
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