Water hyacinth: declared pest

Page last updated: Monday, 6 July 2020 - 10:01am

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Water hyacinth, floating water hyacinth, (Eichhornia crassipes) is a declared pest in Western Australia (WA). This article describes the nature of the plant with links to requirements land owners/occupiers must adhere to and pest control methods.

Form: aquatic — perennial

Status: present in WA

Water hyacinth is an erect floating perennial herb, reproducing by stolons and from seed. Native to Brazil, this weed was introduced into Australia in the 1890s as an ornamental plant for ponds and aquariums. Water hyacinth is a Weed of National Significance (WoNS).


Stems: Erect, to 60 centimetres long and bearing flowers; or horizontal (stolons), about 10 centimetres long and producing new plants from terminal buds. Hairless.

Leaves: Two types of leaves - up 60 centimetres long, narrow and standing upright; others have an almost round blade up to 30 centimetres diameter and curved upwards with somewhat wavy edges. Both leaf types are smooth and hairless, glossy and have semi parallel veins. Leaf stalks to 50 centimetres long with bladder like swellings, either bulbous or elongated, which contain air cells that enable the plant to float. Dense packed plants mainly have the narrow leaf form.

Flowers: Very attractive, large lilac, funnel shaped four to seven centimetres diameter, with six lobes or petals, the upper lobe with a yellow blotch in the centre surrounded by darker purple; produced in spikes about 15 centimetres long on stalks about the same length. Spikes average about eight flowers but the range can be three to 35. Flowers only last a few days then the flower stalks bend to submerge the fruit.

Fruit: A narrow, three celled capsule 1–1.5 centimetres long containing up to 300 seeds.

Seed: Egg shaped 1–1.5 millimetres long with ribs running the length of the seed.  Seed can remain viable for up to 20 years.

Agricultural and economic impact

An environmental water weed that can block agricultural irrigation channels. Water Hyacinth grows on still or slow-flowing water, in freshwater rivers and other watercourses, lakes, swamps, lagoons on river floodplains, reservoirs and farm dams. 

Declared pest category

The Western Australian Organism List (WAOL) contains information on the area(s) in which this pest is declared and the control and keeping categories to which it has been assigned in Western Australia (WA). Search for water hyacinth in the WAOL using the scientific name Eichhornia crassipes.

Requirements for land owners/occupiers and other persons

Requirements for land owners/occupiers and other persons if this pest is found can be sourced through the declared plant requirements link.

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MyPestGuide™ Reporter
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Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080

Control method

Control methods for this declared plant can be found through the water hyacinth control link.

Contact information

Pest and Disease Information Service (PaDIS)
+61 (0)8 9368 3080
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