Arrowhead: declared pest

Page last updated: Wednesday, 3 June 2020 - 11:47am

Please note: This content may be out of date and is currently under review.

Arrowhead (Sagittaria montevidensis) 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: not present in WA

Arrowhead is native to North and South America.


A perennial or occasionally an annual aquatic weed, to one metre tall.

Stems: Erect 7 to 75 centimetres tall with two to twelve whorls of flowers at the apex.

Leaves: Emergent broadly arrow shaped to 25 centimetres long and 20 centimetres wide with basal lobes 15 centimetres long and 10 centimetres wide. Submerged leaves linear and only sometimes slightly arrow shaped.

Flowers: White and sometimes with a purple patch in the centre, about 2.5 centimetres in diameter in whorls of three lower female and upper are male.

Fruit: A cluster of one seeded fruitlets.

Seeds: Laterally flattened 1.5 to 3 millimetres long, beaked and with dorsal wings.

Agriculture and economic impact

An environmental weed of aquatic and semi-aquatic environmnetts, capable of infesting irrigation and drainage ditches. In dense infestations, decomposing vegetation can cause de-oxygenation of water, and increase populations of disease-carrying insects. 

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 arrowhead in the WAOL. using the scientiific name Sagittaria montevidensis.

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

MyPestGuide™ Reporter
via app or online
(Select 'Send report to MyWeedWatcher' from menu)

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

Control method

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

Contact information

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