Synonyms - Elodea crispa is often used in the aquarium industry.
Family: - Hydrocharitaceae.
Names:
Lagarosiphon is from the Greek lageeos meaning a vine and siphon meaning a tube and refers to the appearance of the leaves and stem.
Major is from the Latin magnus meaning large or long and refers to the long stems.
Lagarosiphon the common name is from the genus name.
Other names:
Oxygen weed
Summary:
A perennial, stoloniferous, floating, aquatic weed with narrow, stiff and curved leaves and long stems
Description:
Cotyledons:
Two.
Leaves:
Alternate and in spirals rather than true whorls. Widely spaced near the base and crowded near the tip.
Stipules -
Petiole - Absent.
Blade - 5-30 mm long by 2-4.5 mm wide, parallel sided to lance shaped, tapering, stiff and curved downwards. Uni cellular spines on the edges. Edges are minutely saw toothed.
Sheath - Absent.
Axillary scales - narrowly triangular with smooth edges.
Stems:
Brittle, curving upwards near the base and downwards near the top or water surface, up to 5000 mm long by 3-5 mm diameter, branching. Root at the lower nodes. Hairless. Stoloniferous. Forms large mats of submerged, intertwined stems.
Flowers:
Separate male and female plants.
Female plant
Single flowered, 3 mm wide. Spathe in upper leaf axils, stalkless egg to narrowly egg shaped. Flower opens at the water surface.
Ovary - 6 thread like hairy stigmas. 6 styles with 3 that are purple with 2 lobes.
Perianth - Tube (hypanthium) up to 150 mm long.
Sepals - 3, spreading
Petals - 3, spreading
Stamens - 3 tiny staminodes
Male plant (not recorded in Australia or NZ)
100 or more flowers. Spathe in upper leaf axils, stalkless, egg shaped.
Flowers detach and float freely.
Perianth - absent.
Sepals - 3, bent back.
Petals - 3, bent back.
Stamens - 6, 3 fertile and held horizontally. 3 sterile and held vertically to act as sails
Fruit:
Egg to narrowly egg shaped. Not produced in Australia.
Seeds:
Narrowly elliptical, 2 mm long by 0.7 mm wide. Not produced in Australia.
Roots:
Fine roots from the basal nodes of the stem.
Key Characters:
Spiral, bent back leaves. Stems that curve downwards at the tips.
Biology:
Life cycle:
Seeds, rhizomes and dormant shoots sprout in spring producing prolific growth of stems and leaves that form large floating masses of tangled stems during summer. Flowering starts in summer and continues until autumn when cooler temperatures induce slow growth and winter dormancy. In Australia and New Zealand only female plants occur, and reproduction is by vegetative means.
Physiology:
Tolerates low P levels.
Concentrates arsenic.
Optimum temperature is 25 degrees C.
Optimum day length is 12 hours.
Optimum light is 17-23% of full daylight.
Maximum growth at 1% bicarbonate.
Root growth limited by red light at shallow depths and blue light at greater depths.
Pressures above 165 kPa (about 6.5 metres deep) usually kills it.
Reproduction:
By seed, rhizomes and stem fragments.
Flowering times:
Summer to autumn.
Seed Biology and Germination:
Vegetative Propagules:
Rhizomes and stem fragments.
Hybrids:
Allelopathy:
Population Dynamics and Dispersal:
The major and most important method of spread is through sale by the aquarium industry and discarding of plants into water courses.
Rhizome extension increases the size of colonies. Stem are brittle and break at the nodes. These fragments move in the water flow then sink and take root in the bottom mud to form new colonies.
Origin and History:
Southern Africa. Naturalised in parts of Europe and in New Zealand.
Distribution:
It is not naturalised in Australia but the practice of selling it for use in aquaria may result in it becoming established as a result of surplus material being discarded.
It has been found in Sydney and in a farm dam near Melbourne.
All infestations have been eradicated.
Habitats:
Permanent still or slow flowing fresh water, 200-7000 mm in depth and of low turbidity. It is most abundant in sheltered areas where it is protected from waves, wind and turbulence.
Climate:
Temperate.
Soil:
Silty or sandy bottom.
Plant Associations:
Significance:
Beneficial:
Used and oxygenating plant in aquaria.
Detrimental:
Impedes water flow and interferes with its utilisation.
Shades out nearly all other plants.
Heavy infestations deplete oxygen levels resulting in the death of aquatic organisms and fish.
Toxicity:
Not recorded as toxic.
Legislation:
Noxious weed of NSW, NT, QLD, SA, TAS, VIC, WA.
Management and Control:
Mechanical methods are normally used for control. Pulverisers have been effective. Covering the bottom with black plastic has also been used.
Lowering water levels to desiccate the weed mass can give good control.
Diquat is used for herbicidal control.
Fluridone is giving good control also.
Xylene can be used for control aquariums but must not be released into water ways.
Thresholds:
It is an aggressive freshwater weed and a single fragment can lead to a major infestation.
Eradication strategies:
Report any suspected infestations to the Agriculture Department for appropriate control measures.
Herbicide resistance:
Biological Control:
Fish like the white amur and Chinese grass carp are used overseas. Snails also show potential for bio control.
Related plants:
None
Plants of similar appearance:
Lagarosiphon is similar in appearance to Elodea or Hydrilla but the leaves are produced alternately and not in true whorls.