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Jepson Interchange (more information)
©Copyright 1993 by the Regents of the University of California

  • Up-to-date information about California vascular plants is available from the Jepson eFlora.



Robert F. Thorne

Annual, perennial herb, aquatic, freshwater or marine, bisexual, monoecious, or dioecious
Leaves basal or cauline, alternate, opposite, or whorled, generally ± sheathing at base, glabrous
Inflorescence: cyme; flowers 1–few, subtended by ± sheathing, entire or lobed bract; staminate flowers sometimes deciduous, free-floating
Flower radial; perianth tube 0 or much elongated, peduncle-like in flower; sepals (0)3, green; petals (0)3, colored or white; stamens (1)3–many, generally in 1+ series; ovary inferior, chamber 1, placentas parietal or basal, ovules 1–many; style lobes generally 3, linear, lobed or notched
Fruit: achene or berry-like and dehiscing irregularly, linear to spheric, submersed
Genera in family: ± 17 genera, ± 130 species: worldwide; some cultivated for aquaria, others noxious weeds.



Perennial, rooted in mud, submersed or floating, dioecious (CA plants staminate)
Stem slender, sometimes branched or not
Leaves opposite below, crowded and whorled above, 3–6 per whorl, sessile
Staminate inflorescence: flowers 2–3, clustered, peduncled; bract slender
Pistillate inflorescence: flower 1, axillary; bract slender, ± tubular
Staminate flower floating; perianth tube elongated, slender, peduncle-like, persistent on plant; stamens 9
Pistillate flower floating; perianth tube elongated, slender, peduncle-like, persistent on plant; stigmas 3, 3–4-lobed
Species in genus: 2 species: South America
Etymology: (Latin: a mythical water nymph)


E. densa Planch.

Stem 2–3 mm thick
Leaf 2–4 cm, 2–5 mm wide, narrowly oblong; margin finely serrate
Staminate flower: perianth tube < 6 cm; petals 8–10 mm, white, ± round
Pistillate flower: perianth tube < 6 cm; petals 6–7 mm, white, ± round
Chromosomes: 2n=48
Ecology: Streams, ponds, sloughs
Elevation: < 2200 m.
Bioregional distribution: n&s Sierra Nevada Foothills, San Joaquin Valley, San Francisco Bay Area, San Jacinto Mountains, East of Sierra Nevada (expected elsewhere)
Distribution outside California: to e US, Europe; native to S.America
Flowering time: Jul–Aug
Staminate plants widely cultivated for aquaria
Synonyms: Elodea d. (Planch.) Casp

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