Lagarosiphon major (Ridl.) Moss, Hydrocharitaceae

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Present on Pacific Islands?  no

Primarily a threat at high elevations?  no

Common name(s): [more details]

English: African elodea, African oxygen weed, lagarosiphon, oxygen weed

French: elodée africaine, grand lagarosiphon

Habit:  aquatic herb

Description:  "Vigorous aquatic perennial.  Stems very fragile, to 1 m long, ± 3 mm in diameter, branched.  Leaves distant below, crowded above, alternate, recurved, stiff, opaque, acute to acuminate, c. 16 x 2 mm, margins minutely toothed.  Flowers 1 per spathe in axils of upper leaves; female flowers with filamentous perianth-tube c. 0.25 mm in diameter, to 6 cm long; perianth-segments pink, 1 mm long, transparent, with obvious midnerve; staminodia 3, less than styles, transparent, white, toothed at tip; styles 3, 1 mm long, bifid, red-purple. Lagarosiphon major may be distinguished from the related Egeria and Elodea by its alternate leaves" (Healy & Edgar, 1980; pp. 29-30). Note: All New Zealand collections have been from female plants. 

Habitat/ecology:  "Freshwater wetlands, lakes, ponds and slow rivers.  This plant grows best in nutrient rich waters. Where invasive, the plant forms dense weed beds in sheltered sites in water of 2-6.5 m depth.  The tall, closely packed stands exclude almost all other species, reducing light levels and affecting water chemistry.  The stems reach the water surface and dense mats may attract large herbivorous birds which may adversely affect the native flora"  (Weber, 2003; p. 226).

In New Zealand, "present in waters to a depth of 6 m" (Healy & Edgar, 1980; pp. 29-30).

Propagation:  Vegetative fragments (Weber, 2003; p. 226).

Native range:  Southern Africa, naturalized in Australia, New Zealand & Mascarenes (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)	Australia (continental)	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011) Naturalized
New Zealand New Zealand	New Zealand (country)	introduced invasive	Healy, A. J./Edgar, E. (1980) (p. 29) Voucher cited: R. Mason 526 (CHR 65739)
New Zealand New Zealand	New Zealand (country)	introduced invasive	Owen, S. J. (1997)

Indian Ocean
Country/Terr./St. & Island group	Location	Cited status & Cited as invasive & Cited as cultivated & Cited as aboriginal introduction?	Reference & Comments
La Réunion (France) La Réunion Island	La Réunion Island	introduced invasive	Lavergne, Christophe (2006) "Naturalisé/±envahissant"
Mascarene Islands Mascarene Islands (Mauritius, La Reunion, Rodrigues)	Mascarene Islands	introduced invasive	U.S. Dept. Agr., Agr. Res. Serv. (2011) Naturalized

Comments:  A declared noxious weed in the United States (GRIN). A serious problem in New Zealand (Healy & Edgar, 1980; pp. 29-30).

Control: 

Physical:  "Small infestations may be removed mechanically, but stem fragmentation must be avoided".

Chemical:  "Chemical control includes spraying with diquat approved for use in aquatic environments"  (Weber, 2003; p. 226).

Additional information:
Information from Non-Native Invasive Aquatic Plants in the United States, Center for Aquatic and Invasive Plants, University of Florida and Sea Grant.
Information from the Global Invasive Species Database.
Fact sheet from the Government of Queensland, Australia. (PDF format).
Weed Management Guide from the Government of Australia. (PDF format).
Weed identification guide from Australia National Weeds Strategy.
Photos and additional information at the Environment Bay of Plenty, New Zealand, web site of the Bay of Plenty Regional Council.
Information sheet from Weedbusters New Zealand.

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

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

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

References:

Cronk, Q. C. B./Fuller, J. L. 2001. Plant invaders. Earthscan Publications, Ltd., London. 241 pp.

Hafliger, E. 1092. Monocot Weeds 3. CIBA-GEIGY Ltd., Basle, Switzerland. 132 pp. plus plates.

Healy, A. J./Edgar, E. 1980. Flora of New Zealand, Volume III: Adventive cyperaceous, petalous & spathaceous monocotyledons. Government Printer, Wellington, New Zealand. 220 pp.

Lavergne, Christophe. 2006. List des especes exotiques envahissantes a La Reunion. Unpublished manuscript (Excel file). .

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

Smith, Nicholas M. 2002. Weeds of the wet/dry tropics of Australia - a field guide. Environment Centre NT, Inc. 112 pp.

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

Weber, Ewald. 2003. Invasive plants of the World. CABI Publishing, CAB International, Wallingford, UK. 548 pp.