Lagarosiphon major

Common Name(s): African eoldea

Not Present in Florida

Origin: Temperate and tropical Eurasia and Northern Africa1
Introduction to Florida: 1940s (ornamental)2

This species appears on the following legally prohibited plant lists

LAGAROSIPHON MAJOR (Roxb.) (Ridley) Moss
African elodea, oxygen weed
Hyrocharitaceae/frog’s bit Family

pronounced: lag ar o si fon mah yor
from: lagaros (G.): narrow, thin
siphon (G.): tube
poly (G.): many
major (L.): larger
“likely refers to the long, thin tubes that allow the female flowers to reach the water surface”


Elodea crispa (by those who keep aquaria (Mason 1960)

Happily, Lagarosiphon major does not yet occur in the wild in the United States, as 2008, so far as is known. However, experts have reason to believe that should this plant be introduced to the U.S., the resulting problems could be as consequential as those caused by another plant in the Hydrocharitaceae family, hydrilla (Hydrilla verticillata)


  • Herbaceous perennial
  • strictly aquatic, “obligate” (requiring a wet habitat)
  • in freshwaters, entirely submersed, spreading at surface
  • reproduces from vegetative fragments
  • only female plants are known outside its native range (Cook 1987)
  • growing from bottom to surface in water to 18 feet (6.6 m) deep (Coffey 1988)
  • forming dense stands of stems in the water
  • biomass weight to 424 g m2 dryweight (225 tons of wet biomass per acre) in Lake Taupo, New Zealand
  • can form a light-blocking canopy so dense and thick (3 feet thick) that Lagarosiphon major easily outcompetes even tall non-canopy forming native species (Rattray, Howard-Williams & Brown 1994)
  • 1% light level occurs in as little as .5 m of Lagarosiphon biomass
  • because this plant produces roots faster, grows faster both in length and biomass than one of New Zealands native milfoils, Lagarosiphon major “has an early competitive advantage which may explain the dominance this species now has in the littoral zones of many New Zealand lakes” (Rattray, Howard-Williams & Brown 1994)
  • Lagarosiphon major successfully out-competed native species wherever it has colonised New Zealand lakes in the depth zone 2-6 m–normally occupied by native milfoils (Myriophyllum spp.) and pondweeds (Potamogeton spp.).” (Rattray, Howard-Williams & Brown 1994)


  • will grow in lakes, rivers, streams and ponds, oligotrophic to eutrophic
  • in its original southern Africa range, it grows in high mountain streams and ponds (Wager 1927)
  • it prefers cooler waters; temperature tolerances: this plant is winter hardy; optimum temperature, 20-23oC (68-74oF); maximum temperature, 25o C (77o F) (Kasselmann 1995)
  • the determinant of its maximum depth (about 7 m) is pressure (in non-light-limited environments) (Coffey 1988)
  • prefers high light intensity; best growth to 600 micro-einsteins/m2/h (Schwarz and Howard-Williams 1993)
  • it is an efficient photosynthesizer and has a low light compensation point, facts which promote its weediness
  • “it may be significant that the three known colonies in Dalmuir (England) are also below a point where warm water is discharged” (Silverside and Raymond 1976)
  • in one study, even though the nutrient conditions in one lake were higher than in the second lake, this plant grew twice as much biomass in the second lake, apparently because of the much higher carbon dioxide concentrations (dissolved inorganic carbon, DIC) in the water of the second lake (Rattray, Howard-Williams & Brown 1991)
  • “the competitive success of L. major may be a consequence of greater tolerance to pH stress” than Elodea species (James, Eaton & Hardwick 1998)
  • this plant “is not well adapted for growth in ponds that are green with planktonic algae”(McNabb & Tierney 1972)

Lagarosiphon major (Ridley) Moss ex Wager
Original description: Trans. Proc. Roy. Soc. S. Africa 16(2):191-201. 1928.

  • monocot
  • rooted in the hydro-soil by numerous thread-like unbranched roots
  • stems submersed; brittle; 3 mm (1/8 in.) in diameter; growing to 20 feet long; branching every 10-to-12 nodes; reaching the surface to spread into thick mats
  • leaves submersed; greatly recurved; stiff; alternate spirally along the stem; leaves linear to linear-lanceolate; to 16 mm (1 in.) long by 2 mm (1/16 to 1/8 in.) wide; leaves 3-veined with visible midvein; leaf margins minutely toothed; at stem tips, leaves are very densely crowded
  • flowers tiny, transparent to white or pinkish; all parts in 3’s; in its native range, female flowers reach the surface on long thread-like tubes (to 10 in. long); on the surface they bump into and are pollinated by free-floating male flowers (Cook 1987); male flowers form in the leaf axils, after which they rise to the surface where they sail about; staminate spathes enclose many flower buds, carpellate spathes enclose only one flower (Haynes 1988)
  • fruit capsule is beaked; seeds 1/8 in. long, averaging nine to a fruit
  • outside its native range, only female plants are known and thus reproduction is only by vegetative fragmentation

As a submersed, long-stemmed plant having many small narrow leaves, Lagarosiphon major might be confused with three other plants in the U.S. As chance would have it, two of these three other plants are themselves also not native to the U.S.; however they are here, whereas Lagarosiphon is not (early 2008).

It is believed that this plant was in New Zealand for some time before it was recognized as a plant distinct from Elodea canadensis in the 1950s. By the time it was recognized, Lagarosiphon major was already a major weed there. (Healy)

comparison drawingHere is a comparison of all four of these look-alike plants.

underwater hydrilla picture
non- native hydrilla (Hydrilla verticillata ):
— hydrilla leaves have teeth on the margins and a few teeth on the underside midribs, making hydrilla rough to the touch when pulled through the hands; Lagarosiphon major leaves have no teeth on the margins or midribs and are not rough to the touch

elodea drawing native elodea (Elodea canadensis)
— elodea leaves occur in whorls of 3 around the stem, Lagarosiphon major leaves are alternate along the stem

Egeria densa
Egeria densa drawing native lake hygrophila (Hygrophila costata (H. lacustris)): non-native egeria (Egeria densa)
–egeria leaves are in whorls of 4-5 and do not dramatically “recurve”; Lagarosiphon leaves are alternate and greatly recurve


  • Lagarosiphon major is native in southern Africa
  • there are about 15 other species of Lagarosiphon native in southern Africa, Madagascar and India

Distribution in the U.S.

  • Lagarosiphon major does not yet occur in the wild in the United States (early 2008).

The best way to track the spread of invasive aquatic plants may be to identify the drainage basins (watersheds) they have been discovered in. Drainage maps give useful information to eco-managers because drainage maps show precisely where the plants are, making it easier for managers to infer where the plants might go next, and thus where to take preventive measures.

How it got here

Potential to spread elsewhere in U.S.

  • There is no information in the scientific literature as to the potential for Lagarosiphon major to spread in the U.S.
  • One case study from New Zealand suggests that once a submersed weed is introduced, its further distribution is significantly associated with boating and fishing activities (Johnstone, Coffey & Howard Williams 1985).


  • Lagarosiphon major is fast-growing
  • may totally fill the volume of a large shallow lake (to 3 m deep)
  • fills water control channels
  • in New Zealand, Lagarosiphon major is a major aquatic weed problem recorded in many lakes
  • in England, this plant was reported in 1976 as being “well established in scattered localities in the south, now, two decades later, Lagarosiphon major is “actively displacing” Elodea species in “some lentic British waters” (James, Eaton & Hardwick 1998); it was first recorded in England in 1944 (Silverside and Raymond 1976)
  • “within two years of the first record of L. major in the boat harbour it had largely replaced E. canadensis there” (Coffey 1975)
  • within 13 years from its first record on the lake, the plant occupied almost all of the 161 km length of the littoral zone (Howard-Williams 1988)
  • in New Zealand lakes, this plant has attained biomass weights of 165-424 g m2 dryweight; if this plant, like hydrilla, is 99% water, then the weight of the plant as an infestation in the water is in the range of 16500-42400 g m2 (which converts to 88-225 tons of plant biomass per acre)
  • heavy booms protecting hydro-electric power plants’ water intake units “fail when a massive amount of weed is liberated after storms” (Chapman 1974)
  • with its canopy spreading across the top part of the water, it is able to shade out and thus outcompete other submersed species; 1% light level occurs through as little as .5 m of Lagarosiphon biomass (Schwarz and Howard-Williams 1993) (only 1% of the sunlight can pass through as little as 1.5 ft of a Lagarosiphon infestation)
  • in spite of one of its common names, oxygen weed, in a dense infestation of Lagarosiphon major there often is less oxygen present than in the surrounding water: thus dense infestations, “in such quantities confer no oxygen benefit on fish and other animals in the lake” (Chapman 1974)
  • Lagarosiphon major caused a power outage in 1968 when it blocked the intake screens at Aratiatia hydro station in New Zealand
  • the plant is detrimental to recreation in Hamilton Lake and Lake Rotorua, New Zealand


Lagarosiphon major:

aquatic plant harvesting machine
aquatic plant chopping machine
the action of mechanical harvestors and chopping machines causes fragmentation, which helps spread Lagarosiphon major; “if the weed is cut in mid-summer, the infestation (1m or 6 m) is completely restored by the fall” (Chapman 1974)

grass carp, biological control
the herbivorous (plant-eating) biological control fish, the Chinese grass carp, has a moderate feeding preference for Lagarosiphon major (Edwards 1975; Chapman & Coffey 1971)

man applies aquatic herbicidehelicopter applies aquatic herbicide
the aquatic herbicide fluridone was deemed ineffective when used against Lagarosiphon major in a New Zealand lake (Wells & Coffey 1984); as for another aquatic herbicide, diquat, “only minimal herbicidal effects” were noted and so several formulations of diquat were deemed ineffective against the plant in New Zealand streams (Tanner & Clayton 1984) and diquat “is not effective in turbid water” (Clayton 1998); on the other hand, diquat applications are believed to have affected this plant’s growth in Lake Rotoroa (Tanner & Clayton 1990); sodium arsenite herbicide effects on this plant were described as “spectacular” in 1960, but 24 years later, high arsenic levels persisted in soil and plants (Tanner & Clayton 1990), and “little of the original arsenic applied for weed control was lost from the lake between 1959 and 1992” (Clayton & Tanner 1994)

What can you do?

First, clean your boat before you leave the ramp! Transporting plant fragments on boats, trailers, and in livewells is the main introduction route to new lakes and rivers.
But, there’s plenty more you can do to help.

Laws and lists

Lagarosiphon major

  • is “state-listed” by Florida and North Carolina
  • is on the Florida Prohibited Plants list, Florida Department of Environmental Protection
  • is a “Class A Noxious Weed”, North Carolina Department of Agriculture
  • is on the Federal List of Noxious Weeds (USDA/APHIS, 2000)

Want to know more?

The information contained on this wep page was extracted from published scientific literature and agency reports. It is important to know that plant research, like most areas of scientific research, is still relatively young and incomplete–much may have been published about the physiology of one plant but not about its management; much may have been published about how to culture and grow another plant but not about its natural ecology. Thousands of research articles may have been published about one invasive plant, but perhaps only a dozen about another.

If you want to read the research yourself, perhaps to clarify or expand an area of information contained here, or to help determine your own line of research, you are welcome to query the world’s largest collection of international scientific literature about aquatic, wetland and invasive plants, the APIRS bibliographic database, which contains more than 54,000 citations and their content keywords. Or you might want to ask us to do it for you and mail or e-mail the search results to you.

This is the literature about Hygrophila polysperma that was used to develop this web page. More research items about this plant may be found at APIRS:

  • Chapman VJ, Coffey BJ. 1971. Experiments with grass carp in controlling exotic macrophytes in New Zealand. Hydrobiologia 313-323
  • Chapman VJ, JMA Brown, FI Dromoogle and BT Coffey. 1971. Submerged vegetation of the Rotorua and Waitkato Lakes. NZ J. Marine and Freshwater Res. 5(2): 259-79
  • Chapman VJ, JMA Brown, CF Hill and JL Carr. 1974. Biology of excessive weed growth in the hydro-electric lakes of the Waikato River, New Zealand. Hydrobiologia 44(4:349-363
  • Clayton JS, Tanner CC. 1982. An alternative formulation of diquat for control of submerged aquatic weeds. Proc. 35th N.Z. Weed and pest Control Conf. pp. 261-264
  • Clayton JS, Tanner CC. 1994.. Environmental persistence and fate of arsenic applied for aquatic weed control. IN: Arsenic in the Environment, Part I: Cycling and Characterization. JO Nriagu, ED, pp. 345-363
  • Clayton JS, Chapman VJ, Brown JMA. 1980. Submerged vegetation of the Rotorua and Waikato Lakes. New Zealand J. Marine and Freshwater Res. 15:(44):447-487
  • Coffey BT, Wah CK. 1988. Pressure inhibition of anchorage-root production in Lagarosiphon major (Ridl.) Moss: a possible determinant of its depth range. Aquatic Botany 29:289-301
  • Cook CDK. 1982. Pollination mechanisms in the Hydrocharitaceae. In: “Studies on Aquatic Vascular Plants”, J-J Symoens, SS Hooper and P Compere, eds, pp. 1-15, Royal Bot. Society of Belgium, Brussels
  • Cook CDK. 1990. Aquatic Plant Book. SPB Academdic Publishing. 230 pp.
  • Eady F. 1974. The aquatic weed control problem 2. Methods of control. N.Z. J. Agri. Sept:50-53
  • Edwards DJ. 1975. Taking a bite at the waterweed problem. New Zealand J. Agr. 130(1):33, 35-36
  • Haynes RR. 1988. Reproductive biology of selected aquatic plants. Annals of the Missouri Botanical Garden 75(3):805-810
  • Howard-Williams C, Davies J. 1988. The invasion of Lake Taupo by the submerged water weed Lagarosiphon major and its impact on the native flora. New Zealand J. Ecol. 11:13-19
  • Johnstone IM, Coffey BT, Howard-Williams C. 1985. The role of recreational boat traffic in interlake dispersal of macrophytes: A New Zealand Case Study. J. Environ. Management. 20:263-279
  • Lancaster RJ, Coup MR, Hughes JW. 1971. Toxicity of arsenic present in lakeweed. N.Z. Veterinary Journal 19(7):141-5
  • Mason R. 1960. Three waterweeds of the family Hydrocharitaceae in New Zealand. New Zealand J. Science 3(3):382-395
  • Mason R. 1965. Selected water plants of the Waitko. Dept. Scientific and Indust. Research, Botany Div.
  • Matthews LJ. 1960. Aquatic weed control. Proc. New Zealand Weed Control Conf. , 13:58- 61
  • McNabb C. Jr, Tierney D.P. 1972. Growth and mineral accumulation of submersed vascular hydrophytes in pleioeutrophic environs. Techn. Rept. NO. 26, Inst. Water Res., Michigan State Univ. , East Lansing, Michigan, 33 pp.
  • Montiero A, Vasconcelos T. 1998. Management and ecology of aquatic plants. Proc. 10th EWRS Intern’l Symp. on Aquatic Weeds, European Weed Research Soc., 21-25. September 1998, 444 pp.
  • Rattray MR, Howard-Williams C, Brown, JMA. 1994. Rates of early growth of propagules of Lagarosiphon major and Myriophyllum triphyllum in lakes of differing trophic status. New Zealand J. Marine Freshwtaer Res. 28:235-241
  • Rattray MR, Howard-Williams C, Brown, JMA. 1991. The photosynthetic and growth rate responses of two freshwater angiosperms in lakes of different trophic status: Responses to light and dissolved inorganic carbon. Freshwter Biol. 25:399-407.
  • Samways MJ, Stewart DAB. An aquatic ecotone and its significance in conservation. Biodiversity and Conservation 6(10): 1429-1444
  • Schwarz AM, Howard-Willimas, C. 1993. Aquatic weed-bed structure and photosyntesis in two New Zealand lakes. Aquatic Bot. 46: 263-281
  • Silverside AJ, Raymond CJ. 1976. Lagarosiphon major. Glasg. Nat. 19(4):343
  • Tanner CC, Clayton JS. 1984. Control of submerged weeds in flowing water using viscous gel diquat. Proc. 37th N.Z. Weed and Pest Control Conf. , NZWPC Soc., Palmer, pp. 46-49
  • Tanner CC, Clayton JS. 1990. Persistence of arsenic 24 years after sodium arsenite herbicide application to Lake Rotoroa, Hamilton, New Zealand. New Zealand J. Marine Freshwater Research 24:173-179
  • Tanner CC, Clayton JS, Coffey BT. 1990. Submerged-vegetation changes in Lake Rotoroa (Hamilton, New Zealand) related to herbicide treatment and invasion by Egeria densa. New Zeland J. of Marine and Freshwter Research 24(1):45-58
  • Wells RDS, Coffey BT. 1984. Fluridone- Late Rotoiti efficacy trial. Proc. 37th N.Z. Weed and Pest Control Conf., pp. 42-45
  • Wells RDS, Dewinton MD, and Clayton JS. 1997. Successive macrophyte invasions within the submerged flora of Lake Tarawera, Central North Island, New Zealand. New Zealand J. Marine and Freshwater Research 31(4):449-459

Other web sites that treat Lagarosiphon major

Otago Regional Council, New Zealand

USDA Natural Resources Conservation Service

Sea Grant
This web page was authored in June, 2001, by Victor Ramey (Center for Aquatic and Invasive Plants, University of Florida), with significant contribution from Barbara Peichel (Sea Grant, University of Minnesota). The information contained herein is based on the literature found in the APIRS database.

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