Jepson eFlora: Taxon page
Vascular Plants of California
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Egeria densa

Higher Taxonomy
Family: HydrocharitaceaeView DescriptionDichotomous Key
Habit: Annual, perennial herb, aquatic, freshwater or marine, glabrous or hairy; monoecious, dioecious, or flowers bisexual. Leaf: basal, alternate, opposite, or whorled, generally sessile, generally +- sheathing at base. Inflorescence: axillary, terminal, or scapose, cyme or flowers 1, subtended by +- sheathing, entire or lobed bract; staminate flowers sometimes deciduous, free-floating. Flower: generally radial; perianth 0 or tube 0 or elongate, peduncle-like in flower; sepals (0)3(4), green; petals (0)3(4), white or not; stamens (0)2--many, generally in 1+ series; ovary inferior, chamber 1 or falsely 6--9, placentas parietal, 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. Note: Ottelia alismoides (L.) Pers. is a possibly extirpated alien.
eFlora Treatment Author: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes
Scientific Editor: Thomas J. Rosatti.
Genus: EgeriaView Description 

Habit: Perennial herb, submersed, rooted in mud; dioecious. Stem: slender, branched or not. Leaf: opposite below, crowded and in whorls of 3--6 above, sessile, finely to coarsely serrate. Staminate Inflorescence: axillary, sessile; flowers 2--4(5), 1 open at a time; bract slender. Pistillate Inflorescence: [axillary, sessile; flower 1; bract slender, +- tubular]. Staminate Flower: floating; pedicel elongate, peduncle-like, persistent on pl; stamens 9. Pistillate Flower: [floating; perianth tube elongate, peduncle-like; stigmas 3, 3--4-lobed].
Species In Genus: 2 species: South America. Etymology: (Latin: mythical water nymph) Note: Only staminate plants observed outside native range. Egeria najas Planch. expected but not yet found.
Egeria densa Planch.
Stem: 2--3 mm thick. Leaf: 1.2--4 cm, 2--5 mm wide, recurved, narrowly oblong, finely serrate. Staminate Flower: pedicel <= 8 cm; petals 8--10 mm, white, +- round. Pistillate Flower: [as staminate; petals 6--7 mm]. Chromosomes: 2n=46.
Ecology: Streams, ponds, sloughs; Elevation: < 2200 m. Bioregional Distribution: SNF, GV, SnFrB, SnJt, GB; Distribution Outside California: to eastern United States; Europe; native to South America. Flowering Time: Jul--Aug Note: Staminate plants widely cultivated for aquaria.
Synonyms: Elodea densa (Planch.) Casp.
Jepson eFlora Author: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes
Index of California Plant Names (ICPN; linked via the Jepson Online Interchange)
Noxious Weed listed by CDFA
Weed listed by Cal-IPC

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Botanical illustration including Egeria densa

botanical illustration including Egeria densa


Citation for this treatment: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes 2012, Egeria densa, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on May 09, 2021.

Citation for the whole project: Jepson Flora Project (eds.) 2021, Jepson eFlora,, accessed on May 09, 2021.

Egeria densa
click for enlargement
© 2009 Barry Rice

More photos of Egeria densa in CalPhotos

Geographic subdivisions for Egeria densa:
SNF, GV, SnFrB, SnJt, GB
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map of distribution 1
(Note: any qualifiers in the taxon distribution description, such as 'northern', 'southern', 'adjacent' etc., are not reflected in the map above, and in some cases indication of a taxon in a subdivision is based on a single collection or author-verified occurence).


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Data provided by the participants of the  Consortium of California Herbaria.
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All markers link to CCH specimen records. The original determination is shown in the popup window.
Blue markers indicate specimens that map to one of the expected Jepson geographic subdivisions (see left map). Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues.

CCH collections by month

Duplicates counted once; synonyms included.
Species do not include records of infraspecific taxa, if there are more than 1 infraspecific taxon in CA.
Blue line denotes eFlora flowering time (fruiting time in some monocot genera).