Water mimosa (Neptunia oleracea)

Water mimosa is a perennial aquatic plant that grows on the banks of waterways with its stems growing out over the surface of the water.


How does this weed affect you?

Water mimosa impacts waterways when it smothers native vegetation and reduces oxygen levels in the water. Dense rafts of water mimosa also restrict water flow leading to increased flood risks and restricted recreational use.

What does it look like?

Water mimosa plants send down tap roots into the bank, while the stems grow out over the surface of the water. As they age they develop a spongy covering. The leaves are arranged alternatively along the stems and form branchlets. The branchlets have opposite leaves which are sensitive to the touch. The flowers are yellow and occur in clusters that are ball-shaped and on stalks up to 20 cm long. Fruit are up to 28 mm long and 10 mm wide, and contain up to 8 brown seeds up to 5 mm long and 3.5 mm wide. Terrestrial forms of the plant generally have smaller leaves and flowers with no spongy tissue present on the stems.  

Where is it found?

Water mimosa is found in Mexico, Africa, parts of Asia where it is cultivated as a vegetable, Central America and parts of South America. Water mimosa has not been recorded in New South Wales, but has been found growing in several locations in Queensland and the Northern Territory. 

Maps and records

  • Recorded presence of Water mimosa during property inspections (Map: Biosecurity Information System - Weeds, 2017-2023)
    These records are made by authorised officers during property inspections under the Biosecurity Act 2015. Officers record the presence of priority weeds in their council area and provide this to the NSW Department of Primary Industries. Records reflect the presence of the weed on the date of inspection.

How does it spread?

Water mimosa grows out over the surface of waterways in rafts. Plant fragments can break off these rafts and start new infestations. Plants also produce seed. The deliberate planting of stem fragments to be grown for human consumption is one of the main pathways of spread of this plant.

What type of environment does it grow in?

Plants grow best in still to slow moving waterways up to 1 metre deep, and prefer full sun and hot conditions.


Author: Charlie Mifsud

Technical review: Rod Ensbey


Biosecurity Queensland (2016) Water mimosa (Neptunia oleracea or Neptunia plena) Fact sheet, www.daf.qld.gov.au

Northern Territory Government (n.d.) Weed List - water mimosa 

Technigro Australia Pty Ltd (2011), Weed Watch Water mimosa (Neptunia oleracea)

More information

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Herbicide options

Users of agricultural or veterinary chemical products must always read the label and any permit, before using the product, and strictly comply with the directions on the label and the conditions of any permit. Users are not absolved from compliance with the directions on the label or the conditions of the permit by reason of any statement made or not made in this information. To view permits or product labels go to the Australian Pesticides and Veterinary Medicines Authority website www.apvma.gov.au

See Using herbicides for more information.

PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Only products registered for aquatic use)
Rate: One part product to 50 parts water
Comments: Spot spray
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

PERMIT 9907 Expires 31/03/2025
Glyphosate 360 g/L (Only products registered for aquatic use)
Rate: One part product to 9 parts water
Comments: Splatter gun
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
Resistance risk: Moderate

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Biosecurity duty

The content provided here is for information purposes only and is taken from the Biosecurity Act 2015 and its subordinate legislation, and the Regional Strategic Weed Management Plans (published by each Local Land Services region in NSW). It describes the state and regional priorities for weeds in New South Wales, Australia.

Area Duty
All of NSW General Biosecurity Duty
All pest plants are regulated with a general biosecurity duty to prevent, eliminate or minimise any biosecurity risk they may pose. Any person who deals with any plant, who knows (or ought to know) of any biosecurity risk, has a duty to ensure the risk is prevented, eliminated or minimised, so far as is reasonably practicable.
North Coast Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of the plant being introduced to their land. Land managers should eradicate the plant from the land and keep the land free of the plant. A person should not deal with the plant, where dealings include but are not limited to buying, selling, growing, moving, carrying or releasing the plant. Notify local control authority if found.
This Regional Recommended Measure also applies to Neptunia plena
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here

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For technical advice and assistance with identification please contact your local council weeds officer.

Reviewed 2023