Page author: Don Knoke
Potamogeton nodosus
loddon's pondweed, long-leaved pondweed

Distribution: British Columbia south on both sides of the Cascades to Mexico; east over most of the United States.

Habitat: Shallow to rather deep water.

Flowers: June - August

Origin: Native

Conservation Status: Not of concern


Aquatic, herbaceous perennials from slender rhizomes, the stems sub-terete, sparingly branched, up to 2 m. long.


Leaves alternate, the submersed leaves with petioles 2-10 cm. long, the blades lanceolate-elliptic, 10-20 cm. long and 1-2 cm. broad, thin; floating leaves leathery, long-petiolate, elliptic, 5-12 cm long and 2-4 cm. broad; stipules 4-8 cm. long.


Flowers perfect, in densely-flowered spikes with up to 15 whorles, 2-6 cm. long; peduncles thicker than the stems; perianth of 4 clawed segments, each with an upturned, oval blade; stamens 4, fused with the claws; pistils 4, sessile.


Achenes obovoid, 3-4 mm. long, with a sharp dorsal keel and prominent lateral keels.

Accepted Name:
Potamogeton nodosus Poir.
Publication: Encyclopedie Methodique. Botanique ... Supplement. 4(2): 5354. 1816. 1816.

Synonyms & Misapplications:
Potamogeton americanus Cham. & Schltdl. [Abrams]
Additional Resources:

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

WA Flora Checklist: Potamogeton nodosus checklist entry.

E-Flora BC: Potamogeton nodosus atlas page.

CalPhotos: Potamogeton nodosus photos.

USDA Plants: Potamogeton nodosus information.

12 photographs:
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