Pacific Island Ecosystems at Risk (PIER)

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Azolla pinnata
R.Br., Salviniaceae
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Present on Pacific Islands?  yes

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: feathered waterfern, ferny azolla, greem azolla, mosquito fern, water velvet

Japanese: a-aka-ukikusa, b-aka-ukikusa, o-aka-ukikusa

Habit:  aquatic fern

Description:  "Plants small, 1.5 - 2.5 cm long, with a +/- straight main axis with pinnately arranged side branches, progressively longer towards the base, thus roughly triangular in shape, the basal branches themselves becoming pinnate and eventually fragmenting as the main axis decomposes to form new plants. Roots with fine lateral rootlets, having a feathery appearance in the water. Leaves minute, 1 -2 mm long, overlapping in 2 ranks, upper lobe green, brown green or reddish, lower lobe translucent brown; minute, short, pale, +/- cylindrical unicellular hairs often present on the upper lobes. When fertile, round sporocarps 1 - 1.5 mm wide can be seen on the under side at the bases of the side branches. The leaves often have a maroon-red tinge and the water can appear to be covered by red velvet from the distance. The upper surface of the leaves are totally water-repellant, and if completely submerged the plants quickly refloat with the right side up." (Croft, 1986).

Habitat/ecology:  "It is found in tropical regions and in lakes, marshes, ponds, paddy fields, ditches and rivers of warm temperature.  Wave and wind action reduce growth and fragment the plants, thus it seldom occurs in large lakes or rapidly moving water.  Because it is not dependent upon N in the water and is free-floating, it can inhabit areas other weeds cannot" (Holm et al., 1997; p. 95).  Forms dense mats that choke out other species.

Propagation:  Spores and vegetatively.  "Its rapid expansion under proper environmental conditions is the result of vegetative reproduction that occurs when an abscission layer forms at the base of lateral rhizome, allowing it to separate from the main rhizome.  A small root is present on the detached branch" (Holm et al., 1997; p. 96).

Native range:  "Africa and Madagascar, India, Southeast Asia, China and Japan, Malaya and the Philippines, the New Guinea mainland and Australia."  (Croft, 1986)

Presence:

Pacific
Country/Terr./St. &
Island group
Location Cited status &
Cited as invasive &
Cited as cultivated &
Cited as aboriginal introduction?
Reference &
Comments
Marshall Islands
Ratak Chain
Majuro (Mãjro) Atoll introduced
Vander Velde, Nancy (2003) (p. 14)
Rare or now extirpated.
New Caledonia
New Caledonia
New Caledonia Islands native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
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
Waterhouse, D. F. (1993) (pp. 63, 76)
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)
Victoria
Australia
Australia (continental)
New South Wales native
Australian Biological Resources Study (2013)
Australia
Australia (continental)
Northern Territory native
Australian Biological Resources Study (2013)
Australia
Australia (continental)
Queensland native
Australian Biological Resources Study (2013)
Cambodia
Cambodia
Cambodia (Kingdom of) native
Waterhouse, D. F. (1993) (pp. 63, 76)
China
China
China (People's Republic of) native
cultivated
U.S. Dept. Agr., Agr. Res. Serv. (2013)
Anhui, Fujian, Henan, Hubei, Jiangsu, Jiangxi, Sichuan, Zhejiang
Indonesia
Indonesia
Indonesia (Republic of) native
Waterhouse, D. F. (1993) (pp. 63, 76)
Japan
Japan
Japan (country) native
U.S. Dept. Agr., Agr. Res. Serv. (2013)
South Korea
South Korea
South Korea (Republic of)   Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James (1997) (p. 93)
Malaysia
Malaysia
Malaysia (country of) native
Waterhouse, D. F. (1993) (pp. 63, 76)
Negara Brunei Darussalam
Brunei
Brunei (Negara Brunei Darussalam) native
Waterhouse, D. F. (1993) (pp. 63, 76)
New Zealand
New Zealand
New Zealand (country) introduced
invasive
Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. (1988) (p. 36)
"Ponds and lakes".
Singapore
Singapore
Singapore (Republic of) introduced
invasive
Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 17)
Naturalised
Thailand
Thailand
Thailand (Kingdom of) native
Waterhouse, D. F. (1993) (pp. 63, 76)
Vietnam
Vietnam
Vietnam (Socialist Republic of) native
cultivated
Waterhouse, D. F. (1993) (pp. 63, 76)

Comments:  On US noxious weed list.

In New Zealand, Azolla pinnata has replaced a native floating fern, Azolla rubra, over most of northern New Zealand (Owen, 1997).

Azolla lives in symbiosis with blue-green algae (cyanobacteria), taking advantage of their ability to fix nitrogen. It is sometimes introduced and used by farmers as a natural fertilizer for this reason.

Additional information:
Fact sheet on A. pinnata in Papua New Guinea (from "The Aquatic Pteridophytes of New Guinea")
Fact sheet from North Carolina State University
Photos of it growing in Canberra, Australia.
Information from the Global Invasive Species Database.
Information from the ASEAN Tropical Plant Database.

Additional online information about Azolla pinnata is available from the Hawaiian Ecosystems at Risk project (HEAR).

Information about Azolla pinnata as a weed (worldwide references) may be available from the Global Compendium of Weeds (GCW).

Taxonomic information about Azolla pinnata may be available from the Germplasm Resources Information Network (GRIN).

References:

Australian Biological Resources Study. 2013. Flora of Australia Online. Australian Biological Resources Study, Canberra.

Australian National Botanic Gardens. 2013. Australian plant common name database. Online resource.

Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. 2009. A checklist of the total vascular plant flora of Singapore: native, naturalised and cultivated species. Raffles Museum of Biodiversity Research, National University of Singapore. 273 pp.

Croft, J. R. 1986. The Aquatic Pteridophytes of New Guinea (online resource).

Holm, Leroy/Doll, Jerry/Holm, Eric/Pancho, Jaun/Herberger, James. 1997. World weeds: natural histories and distribution. John Wiley & Sons. 1129 pp.

Owen, S. J. 1997. Ecological weeds on conservation land in New Zealand: A database. Working draft. Wellington, New Zealand. Department of Conservation.

U.S. Dept. Agr., Agr. Res. Serv. 2013. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

Vander Velde, Nancy. 2003. The vascular plants of Majuro Atoll, Republic of the Marshall Islands. Smithsonian Institution, Atoll Research Bulletin No. 503:1-141.

Waterhouse, D. F. 1993. The major arthropod pests and weeds of agriculture in Southeast Asia. The Australian Centre for International Agricultural Research, Canberra. 141 pp.

Webb, C. J./Sykes, W. R./Garnock-Jones, P. J. 1988. Flora of New Zealand, Volume IV: Naturalised pteridophytes, gymnosperms, dicotyledons. Botany Division, DSIR, Christchurch. 1365 pp.


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This page was created on 1 JAN 1999 and was last updated on 5 NOV 2011.