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.
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Pest and Disease Information Service (PaDIS)
Control methods for this declared plant can be found through the arrowhead control link.