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Parthenium hysterophorus


This is an annual herb which grows to 1.5 metres.

Stem is erect with distinct ribs. It becomes woody and develops branches in its top half when mature. Leaves are pale green, deeply lobed and covered with fine, soft hairs. Leaves are arranged on alternate areas of the stem.

Flowers are small, diamond shaped and creamy-white in colour. It flowers during spring, summer and autumn.

Seeds of 4 to 5 are contained in each flower. They are small and black seeds that are wedge shaped with 2 thin, white scales.

Habitat this species colonises weak pastures with sparse ground cover. It grows in most soil types but becomes dominant in alkaline, loamy soils and on river banks, particularly where vegetation has been overgrazed.

Weed characteristics are allergic reactions when contact with the plant or the pollen occurs. Its presence reduces the reliability of improved pasture establishment and reduces pasture production potential.

Dispersal seeds can spread by water, vehicles, machinery, stock, feral and native animals, and in feed and seed.

Declaration Details

This species is a Class 2 declared plant under Queensland legislation and is listed as a Weed of National Significance.

How to act

Spraying with a selective broad leaf herbicide prior to seed set is recommended. Improved grazing practices that minimise disturbed bare ground and maximise competing grasses are essential. Fencing areas to prevent stock movement while spraying will reduce further spread. Hand removal of individual or isolated plants prior to seed set is effective. Ongoing monitoring for up to seven years for emergent seedlings is recommended.

Refer to Weed Control Methods.


Related information

Parthenium © NQ Dry Tropics 2010
Parthenium © NQ Dry Tropics 2010
Parthenium © NQ Dry Tropics 2010
Parthenium © NQ Dry Tropics 2010
Parthenium © NQ Dry Tropics 2010
Parthenium © NQ Dry Tropics 2011
Parthenium © NQ Dry Tropics 2011

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