Water mimosa

Scientific name: Neptunia plena
Declaration status: Class A

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 (NT).

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 NT.

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.

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.

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

  • semi aquatic, floating perennial herb can grow on land in damp soil or in water as thick floating mats
  • stems grow out over water that make a thick spongy covering that helps the plant float
  • olive-green bipinnate leaves, 5mm to 18mm long and 1.5mm to 3.5mm wide in opposite pairs along the stem
  • when disturbed or touched the leaflets close up and when plants growing on land have smaller leaves
  • small, yellow almost rounded flower clusters borne on thin stalks 5cm to 20cm long
  • thick taproot becomes woody with age and produces stems up to 1.5m long that can be detached.

Water mimosa - stems and branchesWater mimosa - flowerWater mimosa - rootsWater mimosa - spreadWater mimosa - infestation

To find out more, get the water mimosa weed note on the Department of Environment, Parks and Water Security website.

If you are unsure, contact the Weed Management Branch.

Similar looking plants

The following plant species look similar to water mimosa:

Sensitive weed (mimosa pudica)

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.

Find out more about mimosa.

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: 31 May 2022

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