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Myriophyllum aquaticum

Higher Taxonomy
Family: HaloragaceaeView Description 

Habit: [Annual, shrub] perennial herb, generally aquatic or semiterrestrial, dioecious or monoecious. Leaf: cauline, opposite, alternate or whorled; submersed blades pinnately divided, segments thread-like; emergent leaves simple, entire to divided. Inflorescence: raceme, spike, or panicle; flowers 1 or clustered, short-pedicelled to +- sessile. Flower: generally unisexual, small; calyx tube short, fused to ovary, lobes 2--4; petals generally 2--4; stamens 4 or 8, filaments generally short; ovary inferior, chambers 1--4, styles 2--4, separate, stigmas generally plumose. Fruit: fleshy or of nut-like mericarps, dehiscent or not. Seed: generally 1 per chamber.
Genera In Family: 6--8 genera, +- 100 species: especially southern hemisphere, some cultivated. Note: Haloragis erecta (Murray) Eichler not naturalized in California.
eFlora Treatment Author: Adolf Ceska & Oldriska Ceska
Scientific Editor: Bruce G. Baldwin.
Genus: MyriophyllumView DescriptionDichotomous Key

Habit: Plant from rhizomes, occasionally with overwintering buds (late in growing season); occasionally terrestrial. Stem: simple or branched, generally green. Leaf: submersed leaves generally whorled, 3--6 per node; emergent leaves entire to pinnately divided, occasionally bract-like. Inflorescence: generally emergent, spike-like, simple or branched, terminal, flowers in whorls. Flower: proximal pistillate, middle occasionally bisexual, distal staminate; calyx lobes 4; petals generally 4, ephemeral on staminate flowers, minute or 0 on pistillate flowers; stamens generally 8; ovary 4-chambered. Fruit: mericarps 4, nut-like.
Species In Genus: +- 60 species: worldwide. Etymology: (Greek: many leaves, from leaf segments) Note: Myriophyllum specimens best collected in flower or fruit.
Unabridged Note: Plants should be washed first and then "floated" on the herbarium mounting paper in a shallow dish with water [see Ceska & Ceska 1987 Ann Missouri Bot Gard 73:825--827].
Reference: Ceska et al. 1986 Brittonia 38:73--81

Myriophyllum aquaticum (Vell.) Verdc.
Habit: Dioecious; winter buds 0. Stem: < 1 m, bright green to +- gray-green, leafy throughout. Leaf: submersed leaves 1.5--3.5 cm, length 3--4 × width, segments 20--30 per leaf, +- 7 mm. Inflorescence: terminal, generally emergent. Staminate Flower: stamens 8; ovary vestigial. Pistillate Flower: stamens 0. Fruit: generally 0 (in California).
Ecology: Common. Ponds, streams, lakes; Elevation: < 500 m. Bioregional Distribution: NCo, NCoR, CaRF, SNF, GV, CCo, SnFrB, SCo, DMoj; Distribution Outside California: southern and eastern United States, warm temperate, tropics worldwide; native to South America. Flowering Time: Jul--Sep Note: Plants generally pistillate (staminate unknown in California), clonal; forms dense colonies with emergent branches; escaped from original plantings as ornamental.
Unabridged Synonyms: Myriophyllum brasiliense Cambess.; Myriophyllum proserpinacoides Gillies ex Hook. & Arn.
eFlora Treatment Author: Adolf Ceska & Oldriska Ceska
Reference: Ceska et al. 1986 Brittonia 38:73--81
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Citation for this treatment: Adolf Ceska & Oldriska Ceska 2012, Myriophyllum aquaticum, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on July 21, 2018.

Citation for the whole project: Jepson Flora Project (eds.) 2018, Jepson eFlora,, accessed on July 21, 2018.

Myriophyllum aquaticum
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© 2013 Neal Kramer
Myriophyllum aquaticum
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© 2005 George W. Hartwell
Myriophyllum aquaticum
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© 2013 Neal Kramer

More photos of Myriophyllum aquaticum in CalPhotos

Geographic subdivisions for Myriophyllum aquaticum:
NCo, NCoR, CaRF, SNF, GV, CCo, SnFrB, SCo, DMoj;
Markers link to CCH specimen records. Yellow markers indicate records that may provide evidence for eFlora range revision or may have georeferencing or identification issues. Purple markers indicate specimens collected from a garden, greenhouse, or other non-wild location.
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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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.