Page authors: Don Knoke, David Giblin
Zannichellia palustris
horned pondweed

Distribution: Occurring on both sides of the Cascades crest in Washington Alaska to California, east across most of North America to the Atlantic Coast.

Habitat: Fresh to brackish, standing to slow-flowing water, sea level to moderate elevations in the mountains.

Flowers: June-August

Origin: Native

Growth Duration: Perennial

Conservation Status: Not of concern

Pollination: Self-pollination


Monoecious, submersed, aquatic perennials from slender rhizomes, the stems nearly filiform, freely branching.


Leaves opposite, hair-like, 1-nerved, 2-10 cm. long; stipules free, membranous.


Flowers naked, axillary, the staminate and pistillate usually in the same axil; staminate flowers a single stamen, the slender filament much exceeding the pistil; pistillate flowers of 2-8 distinct carpels; style short, stigma peltate.


Achenes sickle-shaped, 3-4 mm. long, compressed and keeled, with a short stipe and slender stylar beak 1 mm. long.

Accepted Name:
Zannichellia palustris L.
Publication: Sp. Pl. 2: 969. 1753.

Synonyms & Misapplications:
Zannichellia palustris L. var. stenophylla Asch. & Graebn. [Peck]
Additional Resources:

PNW Herbaria: Specimen records of Zannichellia palustris in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Zannichellia palustris checklist entry.

OregonFlora: Zannichellia palustris information.

E-Flora BC: Zannichellia palustris atlas page.

CalPhotos: Zannichellia palustris photos.

USDA Plants: Zannichellia palustris information.

11 photographs:
Group by