Water lettuce: declared pest

Page last updated: Monday, 4 May 2020 - 5:29pm

Please note: This content may be out of date and is currently under review.

Water lettuce (Pistia stratiotes) 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

Status: present in WA


A free-floating plant widespread throughout the tropics, with a dense rosette of overlapping leaves on a very short stem and long feathery roots. Reproduces vegetatively and by seed.

Stems: To 60 centimetres long, linking the rosettes.

Leaves: Pale yellow-green or grey-green, fan shaped, with six or more prominent veins on the under surface, 2.5-15 centimetres long and to eight centimetres wide, densely covered with short white hairs which trap air and give the plant the ability to float.

Flowers: Inconspicuous, surrounded by a small leaf-like bract 7-12 millimetres long and five millimetres wide that encloses the minute male and female flowers.

Fruit: Fleshy, five to eight millimetres diameter.

Seed: Each seed is two millimetres long. Green at first brown when mature, oblong with a thick wrinkled coat, four to 15 seeds per fruit.

Agricultural and economic impact

An environmental water weed, can block irrigation channels.

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). Use the external links on this page to reach water lettuce in WAOL.

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.

Search > detect > report

Report: this pest to the Pest and Disease Information Service using the contact details given below or by using the MyWeedWatcher smartphone and tablet application or online reporting tool.

Control method

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

Contact information

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