Page authors: Don Knoke, David Giblin
Egeria densa
Brazilian waterweed, South American waterweed

Distribution: Occurring chiefly west of the Cascades crest in Washington; southwestern British Columbia to California, east across the southern half of the United States to the Atlantic.

Habitat: Ponds, lakes, and slow-moving water at low elevation.

Flowers: July-September

Origin: Introduced from South America

Growth Duration: Perennial

Conservation Status: Not of concern


Submersed, dioecious perennials, with sparingly-branching and nodally-rooting stems.


Stems very leafy; leaves in whorls of 4 or 6, 2.5-3 cm. long and 2-3 mm. broad, acuminate.


Both pistillate and staminate flowers with a long, thin, stipe-like tubular calyx, enclosed at the base in fused bracts; flowers 1-several in the bracts; calyx lobes 3, 4-5 mm. long, greenish; petals 5, white, twice as long as the calyx lobes; stamens 9; stigmas 3, bi-lobed.


Fruit berry-like, uncommon.

Accepted Name:
Egeria densa Planch.
Publication: Annales des Sciences Naturelles, Botanique. sér. 3, 11: 80. 1849.

Synonyms & Misapplications:
Elodea densa (Planch.) Casp. [HC]
Additional Resources:

PNW Herbaria: Specimen records of Egeria densa in the Consortium of Pacific Northwest Herbaria database

WA Flora Checklist: Egeria densa checklist entry

OregonFlora: Egeria densa information

E-Flora BC: Egeria densa atlas page

CalPhotos: Egeria densa photos

15 photographs:
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