Water mimosa


Have you seen Water mimosa?

Be on the lookout for Water mimosa and report it to Biosecurity Queensland. Early detection and reporting are the key elements in preventing Water mimosa from becoming a major problem in Queensland.

Call us on 13 25 23.

The term 'water mimosa' refers to the species Neptunia oleracea and Neptunia plena. Both are native to Mexico, Central America and northern parts of South America. N. plena also grows in tropical Asia, where it is farmed as a water vegetable.

Water mimosa is an aquatic, nitrogen-fixing legume that releases nitrogen into water bodies. This can lead to increased algal blooms and encourage growth of other weeds such as water hyacinth, water lettuce and salvinia. Excess nitrogen also affects water quality and increases water-treatment costs.

Water mimosa can grow on damp soil or as thick mats on water. It is found in scattered sites across Queensland.

You must manage the impacts of Water mimosa on your land.

You must not give away, sell or release Water mimosa into the environment.

You must report all sightings to Biosecurity Queensland within 24 hours.

Scientific name

Neptunia oleracea, N. plena


  • Floating perennial weed that attaches to bank at water's edge and sends down taproot.
  • Stems to 1.5m long, grow out over water and form spongy, fibrous covering between nodes.
  • Leaves have leaflets, 8–20 pairs per pinna. Leaflets are very sensitive to touch and close quickly.
  • Flowers are yellow, ball-shaped, 30–50 per spike and each flower is 7–16mm long, 0.5–1mm broad.
  • Seeds are oval and brown, 4–8 per legume. Each seed is 4–5.1mm long, 2.7–3.5mm broad.
  • On land, has smaller leaves and flowers, no spongy floating tissue.


  • Grows on land in damp soil or on water as thick floating mats.
  • Commonly found in and around freshwater pools, swamps and canals.


  • Found in South East Queensland.

Life cycle

  • Grows from seeds and stem sections that break free from parent plant.
  • Flowering begins in early summer.

Affected animals

  • Native fish
  • people



  • Restricts water flow in creeks, channels and drains.
  • Increases water loss through evapotranspiration.
  • Reduces water quality by preventing light penetration and reducing oxygenation of water.
  • Creates favourable habitat for mosquitoes.
  • Reduces fish activity.
  • Kills native, submerged water plants and fish.
  • Replaces native wetland plants.


  • Impedes recreational water sports and boating access.

How it is spread

  • Has been subject to sale and distribution through Asian communities and gardeners.
  • Floating rafts of dense inter-woven stems can be dislodged by water movement (especially during floods) and re-establish further downstream.


  • Call 13 25 23 if you find a plant you suspect may be water mimosa to seek advice on control options

Biological control

  • No known biological control agents.

Legal requirements

  • Water mimosa is a category 2, 3, 4 and 5 restricted invasive plant under the Biosecurity Act 2014.
  • You must not keep, move, give away, sell, or release into the environment. Penalties may apply.
  • All sightings of water mimosa must be reported to Biosecurity Queensland within 24 hours of the sighting.
  • You must take all reasonable and practical measures to minimise the biosecurity risks associated with dealing with water mimosa under your control. This is called a general biosecurity obligation (GBO).
  • At a local level, each local government must have a biosecurity plan that covers invasive plants and animals in its area. This plan may include actions to be taken on water mimosa. Some of these actions may be required under local laws. Contact your local council for more information.

Further information