Mimosa

Mimosa is a declared Class A and Class C weed except in areas where it is classified as Class B and Class C (an area roughly described as west of the Kakadu National Park, north of Adelaide River township, north-west of the Daly River / Port Keats Road and north-east of the Moyle River and an area of the Oenpelli floodplain). 

Read the mimosa declaration zone map (547.0 kb).

It is also a Weed of National Significance.

Go to the Weeds of National Significance website for more information.

Mimosa also has a statutory weed management plan (4.1 mb) which outlines the legal requirements for control.

Another name for this plant is Mimosa pigra.

Mimosa - infestation 

Identification

You should use this as a guide. There may be other plants or weeds that look similar.

If you are unsure, contact the Weed Management Branch.

Habit

These features describe the habit of this plant:

  • single prickly stem when young
  • branched prickly bush when mature
  • up to 6m tall.

Mimosa - habit 

Stems and branches

These features can identify the stems and branches:

  • stem is greenish in young plants
  • becomes woody as the plant matures
  • stem prickles are 0.5 to 1cm long
  • forms aerial roots when it is growing in standing water.

Mimosa - stems and branches 

Leaves

These features can identify the leaves:

  • fern-like green leaves
  • made up of many fine leaflets
  • occur in opposite pairs along branches
  • fold together at night, when touched or when water stressed.

Mimosa - leaves 

Flowers

These features can identify the flowers:

  • flower heads are round fluffy balls
  • composed of up to 100 small pink to mauve flowers
  • each flower head produces a cluster of 10-20 seed pods.

Mimosa - flowers 

Fruit and seeds

These features can identify the fruit and seeds:

  • seed pods are 6 to 8cm long
  • turn brown when mature and break into segments
  • seeds within the pods are oblong, brown or green and flattened
  • covered in fine hairs which aid dispersal on water.

Mimosa - fruit and seeds 

Similar looking plants

The following plant species look similar to mimosa:

Mesquite - infestation

Find out more information about mesquite.

Mimosa Bush

Mimosa bush (Acacia farnesiana) is native to Central and South America. It is a rounded shrub or small tree that forms thorny thickets that hinder mustering and stock access to water. It is not a declared weed in the NT.

This table (95.3 kb) can help you to identify a prickle bush that might be mimosa.

Impact

It is estimated that up to 140,000 hectares of land in the Northern Territory (NT), 10% of the Territory’s wetlands, is already impacted by mimosa. It has the potential to spread across wetland areas right across northern Australia. The total area at risk from mimosa infestation in Australia is estimated to be up to 4,600,000 hectares.

Mimosa can have all of the following impacts:

  • forms dense, thorny, monospecific thickets up to 6m tall
  • prevents access to humans and animals and restricts mustering
  • restricts harvesting of bush food by Indigenous people
  • takes over and replaces grasslands
  • reduces carrying capacity of valuable floodplain country
  • harbours feral animals.

Habitat and distribution

Mimosa is native to tropical America from Mexico to northern Argentina.

It was deliberately introduced to the Northern Territory (NT) in the late 1800’s as an ornamental curiosity. Since then, it has spread across 15 catchments and onto three islands in the Northern Territory. In suitable conditions mimosa can form vast monocultures. Its spread has negatively impacted wetland ecosystems, pasture production, conservation land management and social and cultural land use.

There are two known occurrences of mimosa in Australia outside of the NT, one at Lake Proserpine in eastern Queensland, and one in the East Kimberley near Kununurra (WA). Both of these outbreaks are under active management.

In the NT mimosa is particularly invasive on floodplains, wetlands and riparian habitats. Mimosa has become well established in many river systems across the Top End of the NT, including the Fitzmaurice, Daly, Reynolds, Finniss, Adelaide, Mary and the East and South Alligator Rivers. Smaller, satellite infestations have been found on the Arafura Swamp in Arnhem Land, Melville Island, Croker Island and on the Phelps River.

Spread prevention

Mimosa reproduces via seeds. A single plant can produce 200,000 seeds annually. Seeds can then be spread by water, machinery, vehicles, animals and people. Most seeds will germinate with first rains, however the seed's tough outer coating means the seed can remain dormant for many years (up to 20 years in sandy soils).

You can prevent the spread of mimosa by doing all of the following:

  • avoid seeding plants when fishing and boating
  • remove mud that may contain seeds from boats and vehicles before moving to new location* map infestations to help develop a management plan
  • control minor infestations, isolated outbreaks or seedlings first
  • prioritise control along drainage lines, creeks and dams
  • use fencing to control stock and feral animals in areas where there are mature pods
  • quarantine stock when moving from infested paddocks to clean paddocks - seeds can take up to six days to pass through an animal
  • keep a healthy and competitive pasture through managing the impact of grazing, feral animals and fire
  • avoid pasture disturbance around mimosa infestations to limit mimosa seed germination and also in mimosa free areas to limit mimosa establishment
  • avoid driving through infested areas
  • designate wash down areas and actively work to prevent contamination of clean areas
  • monitor areas that you have treated and watch for re-infestations.

Mimosa - spread 

Control

A strategic, integrated and collaborative approach to mimosa management is essential. 

Extensive projects have been implemented involving Indigenous land managers, the pastoral sector and the Territory Government. A range of biological control agents have been released as part of an integrated management program in the NT, some of which have proven very successful.

Chemical control

The best time to treat mimosa with foliar spray is from January to February. When basal barking the best time is from July to November, and when using granular application the best time is from November to December. Below is a list of treatment methods that can be used.

Chemical and concentration Rate Situation, method and notes
Tebuthiuron
Various trade names
1g / m2 Seedling or adult (individuals or infestation):
Granulated herbicide - ground applied
Do not use within 30m of desirable trees or apply to continuous area > 0.5 ha
Do not use if fire is eminent
Apply when there is soil moisture or prior to rain
Fluroxypyr 200 g/L
Various trade names
300mL / 100 L
3 L / 60L water / ha
1:60 (diesel)
Seedling or adult (individuals or infestation):
Foliar application when actively growing
Wetting agent Uptake® required – 500 ml / 100 L
Seedling or adult (infestations):
Aerial control
Seedling or adult:
Basal bark or cut stump application method
Foliar application when actively growing
Fluroxypyr 333 g/LStarane® Advanced 180ml / 100 L
1.8 L / 60 L water / ha 
Seedling or adult (individuals or infestation):
Foliar application when actively growing
Wetting agent Uptake® required – 500 ml/ 100 L
Seedling or adult (infestations):
Aerial control
Metsulfuron-methyl
Various trade names
60g / 60 L water / ha Seedling or adult (infestations):
Aerial control
Non-ionic wetting agent required 100 ml / 100 L
Dicamba
Various trade names
6 L / ha
400mL / 100 L
Seedling or adult (infestations):
Aerial control – Use the wetting agent LI700®
Seedling or adult (individuals or infestation):
Foliar application when actively growing
Glyphosate
Various trade names
ratio 1:1 of water Seedling or adult (individuals or infestation):
Cut stump

Foliar spray - A fine spray with low application pressure enables good coverage of the whole plant.

Basal bark - This method involves spraying around the whole stem up to 300mm from the ground.

Pellet granular - granular chemicals are scattered on the ground around the weed.

Cut stump - the plant is cut off low to the ground and chemicals are applied to the exposed surface of the stump.

Non-chemical control

Hand pulling and grubbing

Weeds, including their roots, are physically pulled out of the ground by hand or using hand tools. This is an effective method of control for individual weeds and recent outbreaks that haven’t released seeds yet, but it requires a lot of labour.

Bulldozing

Bulldozers, chopper rollers or graders are used to clear large weed infestations. This leaves large areas of soil exposed so follow up control or revegetation should be considered.

Fire

Fire as a management technique is most effective when it is used together with other methods. It is useful for mass seedling control if there is a sufficient fuel load.

Biocontrol

Since mimosa biocontrol research began in 1979 fifteen different agents (13 insects and 2 fungal pathogens) have been released against it. Currently there are nine agents actively working to reduce mimosa growth, spread and seed production.

See the how to manage weeds page for more information about the mimosa biocontrol program.

Last updated: 27 June 2017