Water mimosa

Water mimosa is a declared Class A and Class C weed.

Another name for this plant is Neptunia plena.

If you think you may have seen water mimosa, or have this weed on your property, do not attempt to control it. 

Contact the Weed Management Branch immediately for assistance.

Water 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:

  • semi aquatic, floating perennial herb
  • can grow on land in damp soil or in water as thick floating mats.

Water mimosa - habit

Stems and branches

These features can identify the stems and branches:

  • grow out over water
  • make a thick spongy covering that helps the plant float.

Water mimosa - stems and branches

Leaves

These features can identify the leaves:

  • olive-green
  • bipinnate leaves
  • 5 to 18mm long and 1.5 to 3.5mm wide
  • in opposite pairs along the stem
  • when disturbed or touched the leaflets close up
  • plants growing on land have smaller leaves.

Flowers

These features can identify the flowers:

  • yellow
  • small, almost rounded flower clusters 
  • borne on thin stalks 5 to 20cm long.

Water mimosa - flower

Roots

These features can identify the roots:

  • thick taproot
  • becomes woody with age
  • produces stems up to 1.5m long that can be detached.

Water mimosa - roots

Similar looking plants

The following plant species look similar to water mimosa:

Sensitive weed (Mimosa pudica) is native to South America and Central America. It is a low creeping plant that grows mostly in undisturbed shady areas, under trees or shrubs.

Impact

Water mimosa was found in a number of farm dams in south-eastern Queensland in 2006, but all of these known populations have been controlled.

This weed has been found twice in the Northern Territory. 

In 2001 an infestation was found in Virginia, then in 2012 another one was found in Nhulunbuy. 

Both of these infestations have been eradicated and management programs were put in place. These sites continue to be monitored today.

Water mimosa could have all of the following impacts:

  • restrict water flow in creeks and drains
  • increase water loss and reduce water quality
  • create a favourable habitat for mosquitoes
  • reduce fish activity
  • replace native wetland plants
  • restrict recreational water sports and boating access.

Habitat and distribution

Water mimosa grows in the coastal regions of southern North America, Central America, northern South America and tropical Asia. It was deliberately introduced to Australia as an ingredient in stir fries.

Water mimosa prefers canals, ponds and swamps. Plants prefer from 30 to 80cm of slow-moving water, full sun and hot and humid conditions.

There are currently no known infestations of water mimosa in the Northern Territory.

Control

If you think you may have seen water mimosa, or have this weed on your property, do not attempt to control it. 

Contact the Weed Management Branch immediately for assistance.

Water mimosa is on the alert list for environmental weeds. This is a list of weeds that threaten biodiversity and cause other environmental damage.

Last updated: 27 June 2017