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< prev - next > Natural resources management KnO 100372_Water hyacinth control (Printable PDF)
Water hyacinth (Eichhornia Crassipes)
Water hyacinth is an aquatic plant which can live and reproduce floating freely on the surface
of fresh waters or can be anchored in mud. Plant size ranges from a few inches to a metre in
height. Its rate of proliferation under certain circumstances is extremely rapid and it can
spread to cause infestations over large areas of water causing a variety of problems. It grows
in mats up to 2 metres thick which can reduce light and oxygen, change water chemistry,
affect flora and fauna and cause significant increase in water loss due to evapotranspiration.
It also causes practical problems for marine transportation, fishing and at intakes for hydro
power and irrigation schemes. It is now considered a serious threat to biodiversity.
The plant originated in the Amazon Basin and was introduced into many parts of the world as
an ornamental garden pond plant due to its beauty. It has proliferated in many areas and can
now be found on all continents apart from Europe. It is particularly suited to tropical and sub-
tropical climates and has become a problem plant in
areas of the southern USA, South America, East,
West and Southern Africa, South and South East Asia
and Australia. Its spread throughout the world has
taken place over the last 100 years or so, although
the actual course of its spread is poorly documented.
In the last 10 years the rapid spread of the plant in
many parts of Africa has led to great concern.
Figure 1: Water Hyacinth
┬ęPaul Calvert/Practical Action
The plant is a perennial aquatic herb (Eichhornia
crassipes) which belongs to the family Pontedericeae,
closely related to the Liliaceae (lily family). The
mature plant consists of long, pendant roots,
rhizomes, stolons, leaves, inflorescences and fruit
clusters. The plants are up to 1 metre high although
40cm is the more usual height. The inflorescence
bears 6 - 10 lily-like flowers, each 4 - 7cm in
diameter. The stems and leaves contain air-filled
tissue which give the plant its considerable buoyancy.
The vegetation reproduction is asexual and takes
place at a rapid rate under preferential conditions.
(Herfjord, Osthagen and Saelthun 1994).
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