Pacific Island Ecosystems at Risk (PIER)

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Spirodela polyrhiza
(L.) Schleid., Araceae
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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

Chinese: zi ping

English: giant duckweed, great duckweed, greater duckweed, large duckweed, water flaxseed

Japanese: tanenanashi, ukikusa

Habit:  aquatic herb

Description:  "Fronds free-floating on water surface, 2-5 cohering in groups connected by elongate, peltately attached stipes, upper surface dark green, lower surface reddish, obovate to orbicular, (3-) 4-8 (-10) mm long, 2-6 mm wide, with 5-11 (-15) conspicuous radiating nerves that crate a peltate appearance, reproducing primarily by asexual budding, over-wintering buds dark brown and reniform, arising from the reproductive pouches and growing nearly to maturity before separating from the parent plant, roots (4) 5-12, fascicled.  Flowers in sac-like spathes open only at apex, with 2 staminate flowers consisting of a solitary anther and 1 pistillate flower consisting of a single ovary with 1-2 ovules.  Fruit slightly winged.  Seed compressed, smooth or slightly reticulate" (Wagner et al., 1999; p. 1458).

Habitat/ecology:  "The species is a weed problem in the world's leading rice-producing countries and a troublesome problem in the world's waterways.  Giant duckweed is most often found in quiet permanent waters.  In mixtures with other duckweeds, it frequents low-lying roadside ditches, sheltered bays, pockets in floating bogs, and sites where town sewage and farm run-off have made waters nutrient rich.  It is often seen in mixtures with larger aquatic species on the vegetation-choked shores of reservoirs, ponds and lakes.  The plant loves full sun but it also frequents woodland and tall grass ponds where there is always partial shade.  Fast water dislodges large populations and aids in the dispersal of the species.  The duckweed will not tolerate salinity.  It can grow in water and on substrates with a wide range of pH"  (Holm et al., 1997; pp. 802, 804).

In Hawai‘i, "naturalized, or possibly indigenous, occurring in taro paddies, slow-running streams, ponds, and marshes" (Wagner et al., 1999; p. 1458).

Propagation:  Primarily by asexual budding (Wagner et al., 1999; p. 1458).

Native range:  "Nearly cosmopolitan, native to Eurasia, Africa, North America and Australia" (Wagner et al., 1999; p. 1458).

Presence:

Pacific
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
State of Hawaii
Hawaiian Islands
Hawai‘i (Big) Island introduced
invasive
Wagner, Warren L./Shannon, Robynn K./Herbst, Derral R. (1997) (p. 59)
Voucher cited: Stemmermann & Luce 7184 (BISH)
State of Hawaii
Hawaiian Islands
Kaua‘i Island introduced
invasive
Imada, Clyde T./Staples, George W./Herbst, Derral R. (2000) (p. 12)
Voucher cited: C. Imada, W. Char & C. Morden 99-7 (BISH)
State of Hawaii
Hawaiian Islands
Maui Island introduced
invasive
Wagner, Warren L./Shannon, Robynn K./Herbst, Derral R. (1997) (p. 59)
Voucher cited: Degener 8934 (US)
State of Hawaii
Hawaiian Islands
O‘ahu Island introduced
invasive
Wagner, Warren L./Herbst, Derral R./Sohmer, S. H. (1999) (p. 1458)
Voucher cited: Forbes 2517.O (BISH)
Papua New Guinea
Papua New Guinea (eastern New Guinea Island)
Papua New Guinea (eastern New Guinea Island) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Philippines
Philippine Islands
Philippine Islands native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Philippines
Philippine Islands
Philippine Islands native
Merrill, Elmer D. (1925) (p. 190)
Floating on stagnant fresh water at low and medium altitudes.
Pacific Rim
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
Australia
Australia (continental)
Australia (continental) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Australia
Australia (continental)
New South Wales   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 802)
Australia
Australia (continental)
Northern Territory   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 802)
Australia
Australia (continental)
Queensland   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 802)
Cambodia
Cambodia
Cambodia (Kingdom of)   Waterhouse, D. F. (1993) (p. 69)
China
China
China (People's Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Colombia
Colombia
Colombia (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Costa Rica
Costa Rica
Costa Rica (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Ecuador (Mainland)
Ecuador
Ecuador (Republic of) (continental) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
El Salvador
El Salvador
El Salvador (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Guatemala
Guatemala
Guatemala (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Honduras
Honduras
Honduras (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Indonesia
Indonesia
Indonesia (Republic of)   Waterhouse, D. F. (1993) (p. 69)
Japan
Japan
Japan (country) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Japan
Ryukyu Islands
Ryukyu Islands native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
North Korea
North Korea
North Korea (Democratic People's Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
South Korea
South Korea
South Korea (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Malaysia
Malaysia
Malaysia (country of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Mexico
Mexico
Mexico (United Mexican States) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Nicaragua
Nicaragua
Nicaragua (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Panama
Panama
Panama (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Perú
Perú
Perú (Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Singapore
Singapore
Singapore (Republic of) uncertain if introduced
invasive
Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 81)
Weed of uncertain origin
Taiwan
Taiwan Island
Taiwan Island native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Thailand
Thailand
Thailand (Kingdom of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Vietnam
Vietnam
Vietnam (Socialist Republic of) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Also reported from
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
Canada (except British Colombia)
Canada
Canada (country) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
United States (continental except west coast)
United States (other states)
United States (other states) introduced
cultivated
U.S. Dept. Agr., Nat. Res. Cons. Serv. (2013)
United States (continental except west coast)
United States (other states)
United States (other states) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)

Comments:  Reported as possibly an invasive plant in the Hawaiian Islands (Staples et al., 2000).


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This page was created on 13 MAY 2005 and was last updated on 22 JAN 2007.