Common Name: Water Hyacinth

General Information

Eichhornia crassipes is an aquatic plant that can be free-floating in the water or rooting into the mud in shallow water. It grows 50 - 100cm tall[, ].
Considered to be one of the worst weeds in the world, water hyacinth can also be used to remove pollutants from water, provide organic matter for biomass and is edible. The plant is grown as an ornamental plant in tropical and subtropical regions of the world.

This is an extremely fast growing plant. Under favourable conditions it can double the area it is covering every 6 - 15 days. It has escaped from cultivation and become a very invasive weed of water courses in the tropics[], causing great environmental problems in many areas where it has become naturalized. Great care should be taken if introducing it to new ponds, but it is easy to control when grown in confined areas[]. It is extremely important, when removing any plant material from the pond, that it is not released into any other water course[]. Subsistence farmers in Bangladesh face disaster when rafts of water hyacinth weighing up to 300 tonnes per hectare float over their rice paddies. As the floods recede, the weeds remain on the germinating rice, thus killing it[]. Engineers have estimated that the Panama Canal would be impassable within three years without continuous aquatic weed control measures[].

Known Hazards

Eating the plant, which is reported to contain HCN, alkaloids, and triterpenoids, may induce itching[]. Fresh plants contain prickly crystals[].
Plants sprayed with 2,4-D may accumulate lethal doses of nitrates[].

Botanical References

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Range

Tropics. Naturalized in central and southern Portugal[]

Habitat

Thrives in a variety of fresh water habitats, from shallow ponds, marshes, and small streams to large lakes and rivers[]. Moist and boggy areas; at elevations from 200 - 1,500 metres in Nepal[].

Properties

Weed Potential	Yes
Edibility Rating
Medicinal Rating
Other Uses Rating
Habit	Perennial
Height	0.25 m
Growth Rate	Fast
Pollinators	Bees, Insects
Self-fertile	Yes
Cultivation Status	Ornamental, Wild

Cultivation Details

Water hyacinth can succeed in a variety of climates from the subtropical to the tropical zones. It grows best in areas where annual daytime temperatures are within the range 20 - 35°c, but can tolerate 10 - 40°c[]. It can be killed by temperatures of 1°c or lower[]. Plants cannot tolerate water temperatures in excess of 34°c[]. It prefers a mean annual rainfall in the range 1,000 - 3,000mm, but tolerates 600 - 4,000mm[].
Prefers growing in a sunny but cool pool[]. Prefers a pH in the range 6.7 - 7.3, tolerating 5 - 8[].
Azotobacter chroococcum, a Nitrogen-fixing bacteria, may be concentrated around the bases of the petioles but doesn't fix nitrogen unless the plant is suffering extreme nitrogen-deficiency[].

Edible Uses

Young leaves and petioles - cooked[, , ]. Virtually tasteless[, ]. Said to be used as a carotene-rich table vegetable in Formosa. Javanese sometimes cook and eat the green parts and inflorescence[].

Flower spikes - cooked[, ].

Medicinal

The leaf petioles are eaten as a treatment for diarrhoea[].
An infusion of the inflated petioles is used in a bath to treat fevers[].

Agroforestry Uses:

The plant can be removed from the water and used to improve the soil. It can be used as compost material; it can be applied direct to the soil as a green manure (dug into the soil); or can be used as a mulch on top of the soil[].
Dried and cleansed plants can be used as fertilizer and plant mulch[, ].
Water hyacinth roots naturally absorb pollutants, including such toxic chemicals as lead, mercury, and strontium 90 (as well as some organic compounds believed to be carcinogenic) in concentrations 10,000 times that in the surrounding water[].

Other Uses

Water hyacinths are potentially an excellent source of biomass. Through an anaerobic fermentation process, polluted hyacinths can be converted to the natural gas methane - a costly process that may become more economical as supplies of underground natural gas are depleted[]. Eventually, living aquatic plants might serve aboard long-distance manned spacecraft, absorbing wastes and converting carbon dioxide to oxygen, then being themselves converted into food[]. The plant can be cultivated for use in wastewater treatment, and can be incorporated into a system where the biomass is harvested for fuel production[]. Since this biomass is a by-product of wastewater treatment, it has a positive environmental impact, and thus poses no threat as competitor to food, feed, or fibre-producing plants[]. Wilted water hyacinth, mixed with earth, cow dung, and wood ashes in the Chinese compost fashion, can yield useful compost in just two months[]. Although potential yields are incredible, so are the costs of removal or attempted eradication of this water weed. Standing crops have been estimated to produce 100-120 tonnes per hectare per year[].. Under ideal conditions, each plant can produce 248 offspring in 90 days[].

In Africa, fresh plants are used as cushions in canoes and to plug holes in charcoal sacks[].

In Indonesia a home industry has been established producing handicrafts such as lady handbags, slippers, hats, and vests from the elongated dried petioles of water hyacinth[].

Propagation

Seeds can tolerate submersion or desiccation for 15 years and still germinate[]. Scarification, but not light, may be required for germination[].
The fruits usually mature under water and in general a period of 20 days is necessary for the production of ripe seed. When the fruit bursts upon maturity, seeds will sink to the bottom of the water. The seed-coat acts as a physical barrier to germination. However, if the seed-coat is cracked, for example by alternate drying and wetting, germination may occur soon after shedding. On the other hand, there are reports of seeds remaining dormant for a period of about 20 years[].
Division