The water hyacinth is perhaps the first floating water plant we learnt about in school and we were also told that they are fast-growing and troublesome weeds in waterways because of their rapid growth and ability to form dense, impenetrable mats of vegetation which hinder navigation and fishing, obstruct irrigation and drainage of farm land and crowd out other plants. As a result of this, this water plant has earned itself a bad name.
But do you know that the water hyacinth is one beautiful water plant? For those of us who have seen it bloom, you will know what I mean. Water hyacinths are members of the Pontederiaceae family which produce spikes of pretty lavender flowers (like the bulbous hyacinths) on top of lush, shiny leaves. There are two species of water hyacinths that one can can choose from.
The first and most common species is Eichhornia crassipes. The leaves of this plant grow from a rosette and the rounded base of each leaf is inflated and spongy which helps to keep the plant afloat on the water surface. For those of us who have picked up one plant a pond, one will observe that the water hyacinth has feathery, freely hanging roots are almost black in colour. These roots do not anchor the plant to any base and hence a water hyacinth is free to float around. Under optimal growing conditions, water hyacinths are prolific bloomers but each flower is rather short-lived, lasting for at most a day or two.
Plants also propagate rather freely by sending out new plants via stolons like a strawberry plant. Although its growth rate can be a nightmare, people have put the water hyacinth to good use after finding out it has phytoremediation properties as it can soak up soluble heavy metal ions and cyanide in polluted waters. The water hyacinth plant also has abundant nitrogen content and it has been harvested and used a substrate for biogas production.
People have also harvested water hyacinths from overgrown colonies for making green manure, compost and mulch for soil improvement. It is sometimes used as a fodder for animals for buffalos and pigs (this is why in Singapore, the older generation calls this plant as the ‘pig plant’ (猪草)). The water hyacinth is also eaten has a leafy vegetable in Taiwan and Java but do exercise caution before consumption as this plant can be contaminated with toxins if it is harvested from polluted waters.
There is another species of water hyacinth known as Eichhornia azurea and its common name include the creeping water hyacinth, peacock water hyacinth. It is less common in Singapore and its flowers are more lavender in colour and smaller compared to Eichhornia crassipes. One will also notice that the yellow spot in the dorsal petal of this species to be more prominent which is not surrounded by a darker patch of purple seen in Eichhornia crassipes. The plant also adopts a slight different growth habit as it grows along a long stem unlike Eichhornia crassipes which adopts a rosette growth habit. Its roots are also less feathered. Eichhornia azurea is propagated via stem-cuttings instead of separation of its stolons (for Eichhornia crassipes). The stems of this species are used to make furniture and baskets.
Both water hyacinth species are sun-lovers and demand a location with more than 6 hours of direct sunshine to grow well. If they are grown in a shady area, one will notice they will simply disintegrate in a matter of a few days.
Water hyacinths are good for ponds which suffer frequently from algae blooms as they help to soak up excess nutrients! Always keep a look out for the growth of your water hyacinth plants in such a situation – promptly remove excess plants before they invade your pond.
If you are afraid they will take over your pond, grow them in a container of water that has some fertiliser added to it. Note the type of fertiliser added as some are harmful to fish if you intend to have fish in the containerised water garden. Fish is recommended as they help to eat up mosquito larvae.
Interestingly, water hyacinths can also be grown in soil. They do well in soggy soils as long as there is water over their crowns!