Some uses of water hyacinths

Water hyacinth (locally called ‘gondok air’ or keladi buntin)

The stems of water hyacinths are a source of fibers in places such as north-east India, the Philippines, Thailand and Vietnam.

Dried fibers are woven to form braids or cords used for making useful items such as bags, footwear, wreaths, hats, vases, lanterns, and some decorative materials. The fibers are used as raw material for paper.

Due to its abundant nitrogen content, the plant can be used as a substrate for biogas production and the sludge obtained from the biogas. It can be used as feed but it easily accumulates toxins.

As it has a high capacity for uptake of heavy metals such as cadmium, chromium, cobalt, nickel, lead and mercury, it is suitable for biocleaning of industrial wastewater. It can also remove other toxins such as cyanide, making it environmentally beneficial in gold mining areas.

In many areas the plant has become an invasive species, including in New Zealand where it is listed on the National Pest Plant Accord. This stops it from being propagated, distributed or sold. In Louisiana (USA), Kerala in India, Tonlé Sap in Cambodia, it is a serious pest. It has become an invasive species on Lake Victoria in Africa after its introduction in the 1980s.

Uncontrolled, water hyacinth can cover whole lakes and ponds, which badly affects water flow and blocks sunlight, thus killing native aquatic plants. When it decays, it depletes oxygen in the water, often killing fish. A ‘forest’ of hyacinth is a prime habitat for mosquitos, and snails that host parasitic flatworms which cause schistosomiasis (snail fever).

Water hyacinth is often problematic in man-made ponds if uncontrolled, but can also provide oxygen and food for fish if the water is kept clean.

Bodies of water that have already been affected by human activities are often invaded by water hyacinth. They can unbalance natural lifecycles in artificial reservoirs or in eutrophied lakes that receive large amounts of nutrients.

Infestation and control

When hyacinths multiply and cover a large area of water, they eliminate fish and choke waterways for boating and shipping.

It becomes a serious threat when it has mass choked a major river. It is extremely difficult to get rid of as folk in the United States and other countries found out in the early 20th century. They tested various means of eradicating the plants, including using steam and hot water, strong acids, and burning after applying petroleum.

Spraying with saturated salt solution has been tried but was found to be very expensive. Then herbicide was used. The active ingredient was arsenic acid as the optimal cost-effective tool for eradication. This was used until 1905 and then substituted with an arsenic-based compound.

But no matter what, spraying could not completely eradicate the water hyacinth due to the vastness of the affected areas and inaccessibility of some.