Page authors: Don Knoke, David Giblin
Spirodela polyrhiza
duckmeal, common duckmeat, greater duckweed

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

Habitat: Quiet water, ponds, marshes and slow-moving streams

Flowers: July-September

Origin: Native

Conservation Status: Not of concern


Monoecious, fleshy, colonial perennials without leaves or stems, the plant a free-floating, round to obovate body 4-8 mm. long, dark green above and purplish beneath, 5- to 11-nerved; rootlets 5-15 in a cluster in the center of the body.




Flowers enclosed in a triangular pouch on the margin of the body; flowers 3 in each pouch, 2 staminate and 1 pistillate, the staminate a single stamen with a 2-celled anther, the ovary with 2 ovules.


Fruit a utricle.

Accepted Name:
Spirodela polyrhiza (L.) Schleid.
Publication: Linnaea 13: 392. 1839.

Synonyms & Misapplications:
Lemna polyrrhiza L.
Spirodela polyrrhiza (L.) Schleid., orthographic variant [FNA22]
Spirodela polyrrhiza (L.) Schleid. var. masonii Daubs
Additional Resources:

PNW Herbaria: Specimen records of Spirodela polyrhiza in the Consortium of Pacific Northwest Herbaria database.

WA Flora Checklist: Spirodela polyrhiza checklist entry.

E-Flora BC: Spirodela polyrhiza atlas page.

CalPhotos: Spirodela polyrhiza photos.

USDA Plants: Spirodela polyrhiza information.

9 photographs:
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