Parthenium weed

Parthenium weed (Parthenium hysterophorus) is a State prohibited weed.

If you find parthenium weed

If you think you may have seen parthenium weed, please contact us by:

• calling our Customer Service Centre on 136 186, or
• emailing weed.spotters@agriculture.vic.gov.au

Please do not attempt to treat or dispose of this weed yourself. We will treat, remove and dispose of parthenium weed safely, at no cost to the land owner.

Why you must report parthenium weed

Parthenium weed originates from parts of North and South America. It was first discovered in Queensland in 1955 and was thought to be introduced via contaminated machinery during World War Two.

It invades disturbed land such as roadsides, stockyards and overgrazed pastures. It has the potential to infest the semi-arid regions of northern Victoria.

Each plant can germinate, grow and set seed within 4 weeks, resulting in multiple germinations in 1 year. One plant can produce up to 20,000 seeds per year.

Parthenium weed:

• produces chemicals which inhibit the growth of other plants
• can cause dermatitis and hay fever in sensitive individuals
• is toxic to cattle.

It currently infests over eight million hectares of Queensland and is also present in NSW and the Northern Territory. It has not been found in Victoria but there is a high risk that it could be introduced.

Identifying parthenium weed

Parthenium weed is an annual or short-lived herb to 2 m tall.

Leaves are grey-green, deeply divided, 5 to 20 cm in length and covered in fine hairs. The leaves are initially in a flat rosette.

Mature stems have distinct grooves along them and are covered in fine hairs.

Flowers are creamy-white, star-shaped and 4 mm across. They are in open branched clusters above the foliage. Flowering can occur all year round in favourable conditions, but usually in summer.