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Mimosa pigra (Mimosa pigra)

A prickly shrub that has invaded large areas of Top End floodplains, turning open wetlands into dense thickets. In Queensland it is limited to small infestations under eradication.

Key facts

Type: Weed, shrub.

Native to: Tropical America.

Established in: QLD, NT.

Other names: Giant sensitive plant.

Identification

  • Shrub to 6 m with stems armed with broad-based prickles.
  • Fern-like leaves that fold up when touched.
  • Fluffy pink ball-shaped flowers and clusters of hairy, segmented pods.

Where it grows

Floodplains, wetlands and riverbanks in the wet-dry tropics.

Why it matters

  • Replaces native wetland vegetation and waterbird habitat.
  • Blocks access to water for stock and people.

How it spreads

  • Bristly pod segments float and stick to animals, vehicles and clothing.

Control options

  • Report any suspected plant in Queensland or outside known Northern Territory infestations.
  • Registered herbicides, fire and mechanical control combined with biological control.

Hygiene and washdown

  • Check clothing, boats and vehicles for pod segments after working on Top End floodplains.
  • Inspect and clean vehicles, plant and footwear before leaving an infested area, paying attention to tyres, radiators, belly plates, tracks and floor mats.
  • Wash down at a designated bay where runoff is contained and can be monitored for seedlings.
  • Record each washdown so the client has evidence of clean entry and exit.

Classification by state

  • Australia (national): Weed of National Significance. One of 32 nationally agreed priority weeds, managed through national strategies with all states and territories.
  • Queensland: Restricted matter, categories 2, 3, 4, 5. Report it to Biosecurity Queensland within 24 hours; do not give it away, sell or release it into the environment; do not move it; do not keep it. Everyone must also take all reasonable and practical steps to minimise its risks (the general biosecurity obligation).
  • New South Wales: Prohibited matter. It is an offence to deal with it, and you must notify NSW DPIRD as soon as you become aware of it.
  • Victoria: Restricted weed. Where it is a restricted weed, trade in it (including the plant, its seed or contaminated material) is prohibited.
  • South Australia: Declared plant. Depending on the declaration, it can be an offence to move it on public roads or sell it, and landowners may be required to control it on their land.
  • Western Australia: Declared pest (C2), prohibited. C2 Eradication: present in limited areas and targeted for eradication. It must not be brought into WA (prohibited organism).
  • Tasmania: Declared weed. Property managers are required by law to control declared weeds, and their import and sale are prohibited.
  • Northern Territory: Declared weed, Class A and B. Class A: to be eradicated. Class B: growth and spread must be controlled. All declared weeds are also Class C, so they must not be brought into the NT.
  • Australian Capital Territory: Declared pest, prohibited. It is a declared pest throughout the ACT. Dealing with it, such as selling, moving or keeping it, is prohibited.

Legal obligations

Every state and territory places a duty on landholders and people working on land to prevent the spread of invasive species, such as the general biosecurity obligation in Queensland and the general biosecurity duty in New South Wales. Declarations and control requirements differ between states and local government areas, so check the current official list before work starts.

  • Queensland: Biosecurity Act 2014 (Qld), administered by Biosecurity Queensland (13 25 23)
  • Northern Territory: Territory Parks and Wildlife Conservation Act 1976 (NT), administered by NT Department of Lands, Planning and Environment

Sources