Jepson eFlora: Taxon page
Vascular Plants of California
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Hydrilla verticillata

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: HydrillaView Description 

Species In Genus: 1 sp. Etymology: (Greek: in water)
Hydrilla verticillata (L. f.) Royle
Habit: Perennial herb, rooting at nodes, submersed; dioecious. Stem: tuber-like; erect stems elongate, much-branched. Leaf: generally 4--8 per node, sessile, 1--2 cm, 1.5--2 mm wide, oblong, coarsely serrate, midrib prickled abaxially or not, tip generally sharp-pointed. Staminate Inflorescence: flower 1, bract at base of elongate perianth tube, spheric. Pistillate Inflorescence: flower 1, bract at base of elongate perianth tube, +- cylindric. Staminate Flower: deciduous, free-floating; perianth parts 6 in 2 whorls, 3--5 mm; stamens 3. Pistillate Flower: persistent, floating; perianth parts 6 in 2 whorls, 3--5 mm; stigmas 3. Fruit: 5--6 mm, +- fusiform. Chromosomes: 2n=32.
Ecology: Canals, ponds, lakes; Elevation: < 200 m. Bioregional Distribution: NCoRI, n&c SNF, ScV, SCo, D; Distribution Outside California: southeastern and eastern United States, Central America; native to Eurasia, Australia. Flowering Time: Jun--Aug
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 Hydrilla verticillata

botanical illustration including Hydrilla verticillata


Citation for this treatment: Robert F. Thorne, C. Barre Hellquist & Robert R. Haynes 2012, Hydrilla verticillata, in Jepson Flora Project (eds.) Jepson eFlora,, accessed on May 27, 2022.

Citation for the whole project: Jepson Flora Project (eds.) 2022, Jepson eFlora,, accessed on May 27, 2022.

No expert verified images found for Hydrilla verticillata.

Geographic subdivisions for Hydrilla verticillata:
NCoRI, n&c SNF, ScV, SCo, D
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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).


Data provided by the participants of the  Consortium of California Herbaria.
View all CCH records
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).