Water Hyacinth

Eichhornia crassipes (C. Martius) Solms-Laub.

Synonyms - Eichhornia speciosa

Family: - Pontederiaceae.


Eichhornia celebrates a Prussian Minister of Education, J.A.F. Eichhorn.

Crassipes is from the Latin crassus meaning thick and pes meaning foot referring to the swollen petiole.

Water Hyacinth because it grows in the water and resembles the blue ornamental Hyacinth.


A free floating, stoloniferous, aquatic perennial with circular leaves on spongy, swollen stalks. It has blue flowers with 6 petals.




First leaves:

Seedling plants have narrow strap-shaped leaves,


Tufted. Form a rosette at the ends of stolons. Upright and held well above the water surface.

Stipules -

Petiole - Spongy on adult leaves. Relatively short and bulbous when the plants are not crowded but where the population is dense the petioles elongate and are less bulbous and up to 500 mm long. Hairless. They give the plant buoyancy.

Blade - Dark green, smooth, thick, shining, with numerous parallel veins, striped, hairless.

Their are 2 shapes being 1) ovate to circular or kidney shaped, curved or wavy, 20-300 mm long by 20-250 mm wide, (usually about 20-80 mm diameter) and shorter than the flower stalk or 2) lance to strap shaped, erect, flat 300-600 mm long and 20-80 mm wide.


Stolons are free floating or root in mud. Branching and creeping producing new plants at their tips. 100-500 mm long. Hairless. Often linked with neighbour plants to form large mats.

Flower stem - Erect spathe, 2 types, the lower is leaf like. Usually longer than the leaves, erect, 30-500 mm tall and emerge from the leaf axils. Bends down to submerge the flower head after flowering.

Flower head:

Spike, up to 500 mm long, 3-35 flowers on stalks about the same length. Female flowers within lower bracts. 2 leafy bracts below the flower.


Pale mauve-lilac. Lily-like. 40-60 mm across, stalkless. Almost symmetric.

Bracts - Pale, egg shaped, membranous, glossy.

Ovary - Superior, 3 celled, enclosed in perianth tube. Elongated, disc like style. May be 3 styles. Many ovules. Stigma hairy and 3 branched.

Perianth - 6 pale purple to blue petal like segments, 25-40 mm long, united at the base into a curved, greenish tube, Hairy. Uppermost petal has a violet blotch with a yellow centre and 14-20 dark veins.

Stamens - 6, 3 long and 3 short. Hairy filaments attached to the tube.

Anthers - 2 celled. Attached on the back.


Globular, shining, membranous, narrow, 3 celled capsule, 10-15 mm long with up to 300 seeds. The capsule is on a drooping stalk.


Egg shaped, lengthwise ribbed 0.5-1.5 mm long.


Very numerous, slender and feathery, dark, trailing, varying in length, up to 2500 mm long, depending on the depth of the water. Roots emerge from the crowns or rhizomes.

Key Characters:

Petal with violet patch and a yellow centre.


Life cycle:

Perennial. Reproduction is by seed or is vegetative. Seed production is variable, some forms being self-incompatible. Most reproduction is vegetative, plants producing short horizontal stolons, which develop a rosette and fibrous roots from the terminal bud. This rosette produces more stolons and the process is repeated. Plant numbers can double every 5 days. The stolons become brittle with age and break. Single plants or groups of plants broken off from the main group will float off to disperse the infestation. Low temperatures result in slower growth. Cold weather and frosts severely damage the leaves and may result in the death of the plant or the dormant base may re shoot with the onset of warmer conditions in spring.

Seeds sink then germinate in spring in the mud. The seedling floats to the surface and grows the first strap like leaves. Circular adult leaves quickly follow, to form a rosette and develop stolons. Flowering occurs in summer to autumn and each flower only lasts a few days. Plants can flower when they are 3-4 weeks old. After flowering, the stalk bends downwards, the seed being produced in the submerged inflorescence. If the site dries up, the seed remains dormant until the area floods again.


Growth rates of 1 tonne per day per hectare have been achieved.

Loss of water by transpiration is 7.8 times the losses from evaporation from clean water surfaces.

Doesn't tolerate salinity above 1.6%.

Has high tannin contents.

Tolerates acid water down to pH 3.


By seed and stolons.

Flowering times:

Summer to autumn in NSW.

January to May in Perth.

Seed Biology and Germination:

Seed may remain dormant and viable for 15 years.

Seed is dormant for 10-12 weeks after ripening.

Vegetative Propagules:




Population Dynamics and Dispersal:

It can spread extremely rapidly, and one season a single plant has been known to extend to cover 600 square metres. In a study carried out in Louisiana, a single plant produced 248,181 daughter plants in 90 days. Plant numbers can double every 5 days by vegetative reproduction.

Nearly all new infestations result from deliberate planting, disposal of aquarium waste or contamination of bats and canoes.

Origin and History:

Amazon river basin in Brazil.

Introduced to Victoria in the 1890's, WA by 1929 and SA by 1937.

Eradicated from SA in 1954.

Eradicated in NSW.

Eradicated from Perth in 1947. Occasional infestations occur which are controlled.



Water Hyacinth has not been found growing in the wild in Tasmania, but odd plants have been found in gardens, or offered for sale by aquarium supply firms.

Established throughout the tropical regions of the world.


In still or slow flowing, open fresh water, it may persist in low lying areas, which, although not under water, are permanently waterlogged. It prefers water bodies that are nutrient rich.


Tropical, sub tropical and warm temperate regions.


Water or permanently waterlogged.

Plant Associations:



Ornamental aquarium or pond plant.

Can remove pollutants such as gold, cadmium, strontium, mercury, lead, nickel, silver, sodium, chlorine, sulphur, cyanide, bromides, phosphates, ammonia, nitrates and some pesticides including the chlorinated hydrocarbons from water.

Potentially useful for sewerage treatment in warmer climates with 1 ha of water hyacinth required per 2000 people when used in combination with other methods.

Potentially useful as a fertiliser, green manure or mulch and used in mushroom growing as a bedding material after sterilisation. As a fertiliser it is richer than farmyard manure but is more bulky and difficult to transport.

Used for making paper, cardboard, hardboard and particle board.

Used for making ink, carbon black and activated charcoal.

Used as a cattle fodder but requires supplements because it is 95% water when fresh. When chopped dried and mixed with cereals it is used as a feed for pigs poultry and cattle. Most animals apart form rabbits don't find it very palatable because of the tannin content.

Long stalks used in basket and mat making.

Suppresses algae.

Provides shelter for snakes and crocodiles.

It is under investigation for water recycling from sewerage in space programs and treating radioactive waters from nuclear power plants.

It is useful for producing methane; 1 kg fresh weight of plant can produce 250 L of methane and is currently being used by the China and India.

Extracts from the petioles have insecticidal and ovicidal activity.

Root extracts as foliar sprays increase the yield of rice and jute.


Water Hyacinth has been called 'the world's worst weed'.

The matted rafts can be up to 1000 mm thick and block waterways, impede water flow, interferes with hydro electric generators and prevent amenity use of lakes and lagoons, fishing and navigation.

Dense infestations increase water loss through transpiration and reduce the oxygen content of the water, which affects fish.

The rotting dead plants contaminate the water making it unfit for consumption.

Provides breeding grounds for mosquitoes.

Reduces habitat for water birds and nesting sites.

Weed of paddy crops, rice, channels, dams, drains, streams and rivers.


Not recorded as toxic.


Noxious weed of NSW, NT, QLD, SA, TAS, VIC, WA.

Management and Control:

Dredges have been used and are effective if the material removed is dried and burnt. More economical and effective herbicide programs have generally replaced dredging. 2,4-D, metsulfuron, diquat, glyphosate, amitrole and terbutryn are the herbicides most commonly used.

In Australia, the Department of Agriculture should be informed of suspected infestations so this plant can be controlled effectively.


Eradication strategies:

Aerial spraying with 2,4-D in November to December has been used in successful eradication campaigns. A combination of spraying, dredging and biocontrol is usually the most effective method of eradication.

Herbicide resistance:

Biological Control:

Bio control has been successfully used in many situations. 2 weevils and a moth have been released. A mycoherbicide has also given good results, especially when applied with low rates of herbicide or in combination with other agents.

Related plants:


Plants of similar appearance:


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