Neptunia plena (L.) Benth., Fabaceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Risk assessment results:  Risk assessment from the Government of Queensland, Australia (PDF format).

Other Latin names:  Mimosa plena L.

Common name(s): [more details]

Chinese: jia han xiu cao

English: water dead and awake, water sensitive

Habit:  aquatic herb

Description:  "Water mimosa is an aquatic floating perennial herb that attaches to the bank at the waters edge and sends down a taproot. Stems grow out over the water and form a spongy, fibrous covering between the nodes. Fibrous (adventitious) roots grow from the nodes. The rooted land form has smaller leaves and flowers, and has no spongy floating tissue. Leaves are olive green and are arranged in opposite pairs along the stem. When disturbed or touched the leaflets close up. Water mimosa flowers are yellow, ball-shaped and grow from the base of the leaves"  (Queensland Government, 2009).

Habitat/ecology:  "Water mimosa takes root on the banks of watercourses and grows out over the water surface, forming floating rafts. Within its native range, water mimosa is a common floating plant in freshwater pools, swamps and canals at low altitudes of up to 300 m. When water levels fall during the dry season, the plants often perish. The plants prefer slow-moving water 30-80 cm deep, full sun and hot, humid conditions. Shade, brackish water and saline soil adversely affect plant growth. Under favourable conditions, water mimosa grows out from the banks to form floating rafts of dense interwoven stems. These can be dislodged by water movement (especially during floods) and are soon replaced by more water mimosa. These floating rafts can: restrict water flow in creeks, channels and drains, impede recreational water sports and boating access, increase water loss through evapotranspiration, reduce water quality by preventing light penetration  and reducing oxygenation of water, create a favourable habitat for mosquitoes, reduce fish activity, cause the death of native, submerged water plants and fish and replace native wetland plants" (Queensland Government, 2009).

Propagation:  Seed and plant pieces carried by water (Queensland Government, 2009).

Native range:  Southern United States (Texas), Mexico, Central and South America (GRIN).

Presence:

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)	Queensland	introduced invasive	Queensland [Australia] Government (2009)
China China	China (People's Republic of)	introduced	ILDIS Co-ordinating Centre (2011)
Colombia Colombia	Colombia (Republic of)	native	ILDIS Co-ordinating Centre (2011)
Costa Rica Costa Rica	Costa Rica (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Ecuador (Mainland) Ecuador	Ecuador (Republic of) (continental)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
El Salvador El Salvador	El Salvador (Republic of)	native	ILDIS Co-ordinating Centre (2011)
Guatemala Guatemala	Guatemala (Republic of)	native	ILDIS Co-ordinating Centre (2011)
Honduras Honduras	Honduras (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Indonesia Indonesia	Indonesia (Republic of)	introduced	Space, James C./Waterhouse, Barbara M./Newfield, Melanie/Bull, Cate (2004)
Malaysia Malaysia	Malaysia (country of)	introduced	Space, James C./Waterhouse, Barbara M./Newfield, Melanie/Bull, Cate (2004)
Mexico Mexico	Mexico (United Mexican States)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Nicaragua Nicaragua	Nicaragua (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Panama Panama	Panama (Republic of)	native	ILDIS Co-ordinating Centre (2011)
Perú Perú	Perú (Republic of)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)
Singapore Singapore	Singapore (Republic of)	introduced	Space, James C./Waterhouse, Barbara M./Newfield, Melanie/Bull, Cate (2004)
Singapore Singapore	Singapore (Republic of)	introduced invasive	Chong, Kwek Yan/Tan, Hugh T. W./Corlett, Richard T. (2009) (p. 63) Naturalised

Also reported from
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
United States (continental except west coast) United States (other states)	United States (other states)	native	U.S. Dept. Agr., Agr. Res. Serv. (2011)

Control: 

Physical:  "There are no chemicals registered specifically for use against water mimosa. In most instances, the most appropriate method of control is to physically remove the infestation. This can be done by removing all plant matter from the infested water body and pulling plants out of the surrounding banks, ensuring removal of the attached root system. This should be repeated on a regular basis until regrowth ceases. All removed plant parts should then be disposed of in an appropriate waste facility or rubbish bin"  (Queensland Government, 2009).

Additional information:
Additional online information about Neptunia plena is available from the Hawaiian Ecosystems at Risk project (HEAR).

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

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

References:

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.

ILDIS Co-ordinating Centre. 2011. International Legume Database & Information Service. Online searchable database.

Queensland [Australia] Government. 2009. Water mimosa. Department of Primary Industries and Fisheries, Land Protection (Invasive Plants and Animals). PP 149. 3 pp.

Space, James C./Waterhouse, Barbara M./Newfield, Melanie/Bull, Cate. 2004. Report to the Government of Niue and the United Nations Development Programme: Invasive plant species on Niue following Cyclone Heta. UNDP NIU/98/G31 - Niue Enabling Activity. 80 pp.

U.S. Dept. Agr., Agr. Res. Serv. 2011. National Genetic Resources Program. Germplasm Resources Information Network (GRIN). Online searchable database.

U.S. Dept. Agr., Nat. Res. Cons. Serv. 2011. The PLANTS Database. National Plant Data Center, Baton Rouge, LA 70874-4490 USA.

Zhengyi, Wu/Raven, Peter H./Deyuan, Hong. 2011. Flora of China (online resource).