Pistia L.
  • Sp. Pl.: 963 (1753) 

Notes: Distribution: Trop. & Subtrop.

General Description

Small, free-floating, acaulescent, rosulate, perennial, freshwater, aquatic herbs with pendent fibrous roots. Leaves densely pubescent, subsessile; blade very variable in size and shape; primary veins parallel. Inflorescence small, hidden among leaf-bases. Spathe constricted centrally, basal part slightly inflated, convolute, apical part ± erect, expanded, acute-acuminate. Spadix highly reduced, adnate to spathe. Flowers unisexual, lacking perigon. Staminate flowers 2–8, connate into a single whorl borne on a short stipe subtended by shallow basal cup, each flower a synandrium of 2 connate stamens. Pistillate flower solitary, basal, consisting of a single, oblique, unilocular ovary; ovules numerous on single basal placenta, style slender, curved; stigma subspherical. Fruit a thin-walled several-seeded berry, dehiscing by irregular splits. Seeds subcylindric, rugose, with abundant endosperm.

Laticifers absent. HABIT : small, free-floating evergreen herbs with pendent feathery roots, stem very short, acaulescent, stoloniferous. LEAVES : several in a rosette, densely pubescent. PETIOLE : very short, almost absent, sheath very short, ligulate, very thin, scarious at base. BLADE : somewhat spongy, obovate-cuneate to obovate-oblong, apically rounded, truncate or retuse; midrib absent, primary veins subparallel, all arising from base, diverging towards apex, running into margin near apex, strongly prominent on lower surface, higher order venation reticulate. INFLORESCENCE : solitary, very small, much shorter than leaves. PEDUNCLE : very short, pubescent. SPATHE : pubescent without, glabrous within, somewhat constricted centrally, lower margins connate with each other and with ovary wall forming tube, free margins between tube and blade folded between stigma and male organs forming a partition between an upper male chamber and a lower female one, blade erect, ovate, expanded, acute-acuminate. SPADIX : shorter than spathe, mostly adnate to spathe, only the apical male zone free, female zone bearing single gynoecium at base and a thin, green, pouch-shaped flap just below spathe partition, male zone subtended by a thin, marginally lobed, green, annular flap, composed of a basally naked spadix axis supporting a single whorl of 2-8 flowers, axis sometimes extending a little beyond. FLOWERS : unisexual, perigone absent. MALE FLOWER : synandrium composed of 2 connate stamens, thecae dehiscing by single apical slit. POLLEN : inaperturate, ellipsoid-elongate to -oblong, medium-sized (mean 27 µm.), exine plicate with strongly undulate frills running the length of the grain. FEMALE FLOWER : gynoecium obliquely adnate to spadix axis, ovary ovoid, 1-locular, ovules numerous, orthotropous, placenta broad, apparently parietal, probably morphologically basal, style attenuate, bending inwards towards male flowers, stigma small, discoid-subcapitate. BERRY : thin-walled, utricular, several-seeded, ellipsoid, irregularly breaking up and decaying to release seeds. SEED : barrel-shaped, ± subtruncate and excavated at apex and base, testa thick, reticulate-alveolate, thicker and with operculum at micropylar end, embryo obovoid to conoid, endosperm copious.

Diagnostic Description

Free-floating aquatics with pendent feathery roots; leaves rosulate, hairy; leaf blade oblong to wedge-shaped, lacking midrib, primary veins parallel, fine venation reticulate; female zone composed of a single gynoecium; male zone a single whorl of 2-8 flowers; flowers unisexual, perigone absent; male flower a synandrium of two connate stamens.


Tropical wetlands; floating aquatic in open, tranquil, freshwater habitats.


Trop. & Subtrop.


Sp. Pl: 963 (1753) & Gen. Pl., ed. 5: 411 (1754); Engl. in E.P. 73 (IV. 23F): 258 (1920)

Sp. Pl. 963 (1753); F.T.A. 8: 140.

Distribution Map

  • Native distribution
  • Introduced distribution
Found in
  • Africa East Tropical Africa Kenya
  • Tanzania
  • Uganda
  • Northeast Tropical Africa Chad
  • Ethiopia
  • Somalia
  • Sudan
  • Northern Africa Egypt
  • South Tropical Africa Angola
  • Malawi
  • Mozambique
  • Zambia
  • Zimbabwe
  • Southern Africa Botswana
  • Cape Provinces
  • Caprivi Strip
  • Free State
  • KwaZulu-Natal
  • Lesotho
  • Namibia
  • Northern Provinces
  • Swaziland
  • West Tropical Africa Benin
  • Burkina
  • Gambia, The
  • Ghana
  • Guinea
  • Guinea-Bissau
  • Ivory Coast
  • Liberia
  • Mali
  • Mauritania
  • Niger
  • Nigeria
  • Senegal
  • Sierra Leone
  • Togo
  • West-Central Tropical Africa Burundi
  • Cabinda
  • Cameroon
  • Central African Republic
  • Congo
  • Equatorial Guinea
  • Gabon
  • Gulf of Guinea Is.
  • Rwanda
  • Zaire
  • Western Indian Ocean Comoros
  • Madagascar
  • Mauritius
  • Asia-Temperate China China South-Central
  • China Southeast
  • Hainan
  • Eastern Asia Nansei-shoto
  • Taiwan
  • Western Asia Afghanistan
  • Asia-Tropical Indian Subcontinent Assam
  • Bangladesh
  • East Himalaya
  • India
  • Laccadive Is.
  • Maldives
  • Nepal
  • Pakistan
  • Sri Lanka
  • West Himalaya
  • Indo-China Andaman Is.
  • Cambodia
  • Laos
  • Myanmar
  • Nicobar Is.
  • South China Sea
  • Thailand
  • Vietnam
  • Malesia Borneo
  • Jawa
  • Malaya
  • Maluku
  • Philippines
  • Sulawesi
  • Papuasia New Guinea
  • Australasia Australia Northern Territory
  • Queensland
  • Northern America Mexico Mexican Pacific Is.
  • Mexico Central
  • Mexico Gulf
  • Mexico Northeast
  • Mexico Northwest
  • Mexico Southeast
  • Mexico Southwest
  • South-Central U.S.A. Texas
  • Southeastern U.S.A. Florida
  • Louisiana
  • Mississippi
  • Southern America Brazil Brazil North
  • Brazil Northeast
  • Brazil South
  • Brazil Southeast
  • Brazil West-Central
  • Caribbean Bermuda
  • Cuba
  • Dominican Republic
  • Haiti
  • Jamaica
  • Leeward Is.
  • Netherlands Antilles
  • Puerto Rico
  • Trinidad-Tobago
  • Venezuelan Antilles
  • Windward Is.
  • Central America Belize
  • Costa Rica
  • El Salvador
  • Guatemala
  • Honduras
  • Nicaragua
  • Panamá
  • Northern South America French Guiana
  • Guyana
  • Suriname
  • Venezuela
  • Southern South America Argentina Northeast
  • Paraguay
  • Uruguay
  • Western South America Bolivia
  • Colombia
  • Ecuador
  • Galápagos
  • Peru
Introduced into
  • Africa Macaronesia Canary Is.
  • Middle Atlantic Ocean St.Helena
  • Asia-Temperate Middle Asia Kazakhstan
  • Western Asia Palestine
  • Europe Eastern Europe Ukraine
  • Middle Europe Netherlands
  • Southeastern Europe Italy
  • Pacific North-Central Pacific Hawaii
  • Southern America Caribbean Aruba

Included Species


  • 1 Dobignard, D. & Chatelain, C. (2010). Index synonymique de la flore d'Afrique du nord 1: 1-455. Éditions des conservatoire et jardin botaniques, Genève.
  • 2 Govaerts, R. & Frodin, D.G. (2002). World Checklist and Bibliography of Araceae (and Acoraceae): 1-560. The Board of Trustees of the Royal Botanic Gardens, Kew.
  • 3 S.J. Mayo (1985) Araceae. Flora of Tropical East Africa
  • 4 F.n. Hepper (1968) Araceae. Flora of West Tropical Africa 3(1)
  • 5 Gardens, K.""Royal Bot World Checklist of Selected Plant Families. (2008).
  • 6 Mayo, S.J., Bogner, J. & Boyce, P.C. The Genera of Araceae. (Royal Botanic Gardens Kew: 1997).

 Information From

CATE Araceae
Haigh, A., Clark, B., Reynolds, L., Mayo, S.J., Croat, T.B., Lay, L., Boyce, P.C., Mora, M., Bogner, J., Sellaro, M., Wong, S.Y., Kostelac, C., Grayum, M.H., Keating, R.C., Ruckert, G., Naylor, M.F. and Hay, A., CATE Araceae, 14 Dec 2011 . 17 Dec 2011.
  • A All Rights Reserved
Flora of Tropical East Africa (FTEA)
Royal Botanic Gardens, Kew, 2004. eFloras: Iridaceae. [online] Available at: http://kew.org/efloras/ [Accessed 2013-08-02]
  • B All Rights Reserved
  • C http://creativecommons.org/licenses/by-nc-sa/3.0/
Flora of West Tropical Aftrica (FWTA)
Royal Botanic Gardens, Kew, 2004. eFloras: Iridaceae. [online] Available at: http://kew.org/efloras/ [Accessed 2013-08-02]
  • D All Rights Reserved
  • E http://creativecommons.org/licenses/by-nc-sa/3.0/
Global Biodiversity Information Facility
  • F All Rights Reserved
eMonocot. (2010, 1st November). Retrieved Wednesday, 8th February, 2012, from http://e-monocot.org.
  • G Content licensed under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 Unported License
World Checklist of Selected Plant Families
WCSP 2014. 'World Checklist of Selected Plant Families. Facilitated by the Royal Botanic Gardens, Kew. Published on the Internet; http://apps.kew.org/wcsp/ Retrieved 2011 onwards
  • H See http://kew.org/about-kew/website-information/legal-notices/index.htm You may use data on these Terms and Conditions and on further condition that: The data is not used for commercial purposes; You may copy and retain data solely for scholarly, educational or research purposes; You may not publish our data, except for small extracts provided for illustrative purposes and duly acknowledged; You acknowledge the source of the data by the words "With the permission of the Trustees of the Royal Botanic Gardens, Kew" in a position which is reasonably prominent in view of your use of the data; Any other use of data or any other content from this website may only be made with our prior written agreement.