Leafy elodea (Egeria densa)

Also known as: dense waterweed, Egeria

Leafy elodea is a submerged aquatic perennial plant that thrives in shallow, nutrient-rich, slow-moving or stationary water to depths of around seven metres.


How does this weed affect you?

Leafy elodea is a submerged aquatic perennial plant that thrives in shallow, nutrient-rich, slow-moving or stationary water to depths of around seven metres. More cold tolerant than many other aquatic weeds, it thrives in southern Australia.

Leafy elodea was traded as an aquarium and pond plant. Unfortunately, it has escaped and causes problems including restricting water flow, increasing siltation, reducing aquatic plant and animal biodiversity, and interfering with swimming, boating and fishing.

Leafy elodea is native to parts of South America. It has become a problem throughout North and South America, and in England, Japan, New Zealand and South Africa.

What does it look like?

The freshwater plant has cylindrical stems that grow up to 1.5 m long (occasionally up to 5 m). Stems take root at the lower nodes but float for most of their length.

The leaves are oval- to oblong-shaped, generally 1.5–4 cm long, 2–5 mm wide, and found in groups (whorls) of 4–5 at the stem nodes. Lower stem leaves may be opposite or in whorls of 3, while the middle and upper leaves can grow in whorls of 4 to 8. Very fine teeth, only visible by a hand lens, are found along the leaf margins. Dense clusters of leaves appear at the ends of branches which often grow to reach the water surface.

The white flowers (1.2–2 cm wide) are found at the water surface on stems up to 8 cm long. These flowers have three large petals centred by a cluster of generally nine yellow anthers. Male and female flowers grow on separate plants, although only male plants have been found in Australia. Seed production has not been recorded.

Where is it found?

The distribution of leafy elodea in Australia includes rivers, lakes, ponds and dams in coastal and inland southern New South Wales (NSW) and south-east Queensland. It is uncommon in other states and has been banned from sale in the Northern Territory, South Australia, Tasmania and Western Australia.

Maps and records

  • Recorded presence of Leafy elodea during property inspections (Map: Biosecurity Information System - Weeds, 2017-2022)
    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?

The plant spreads when stem pieces break from the main plant. This occurs easily from actions such as boat wash and mechanical harvesting, but also from natural means. The plant is spread from site to site through movement of plant fragments, both deliberate and accidental. Fragments caught on boat trailers, fish traps or other equipment can survive long enough to cause a new infestation when equipment re-enters water. The plant has also been deliberately planted for commercial harvesting purposes.


Rebecca Coventry, Andrew Petroeschevsky, Syd Lisle and Peter Gorham.


  • Parsons, W. T. and Cuthbertson, E. G. (2001) Noxious Weeds of Australia. 2nd Edition. CSIRO Publishing, Collingwood. pp. 61–63.
  • Sainty, G. R. Jacobs, S. W. L. (2003) Waterplants in Australia. 4th edition. Sainty and Associates, Potts Point. pp. 84–85.

More information

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Preventing this weed escaping into waterways is the best way of managing it, particularly in areas that are currently free of the plant.

Remove this plant from aquariums and garden ponds. Dispose of plant material by drying in the sun and burying fragments. Never dump or grow aquarium plants in waterways.

Mechanical harvesting can reduce the bulk of the species but has little value in preventing regrowth and long-term control. Often more plant fragments are produced and these spread further downstream.

The long-term management of this plant is likely to involve both increased and variable water flows and reduced nutrient loading.

Chemical control

When using Clipper herbicide tablets, control is directly related to the amount of sunlight on the water body. Sunny warm conditions give best control. Weeds growing in shaded areas may require additional applications. 

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.

Diquat 200 g/L (Reglone®)
Rate: 5 L /megalitre water
Comments: Apply by injection below the surface or as a surface spray.
Withholding period: Do not use treated water for human consumption, livestock watering or irrigation purposes for 10 days after application. Do not graze or cut sprayed vegetation for stock food for 1 day after application. See label for harvest withholding periods.
Herbicide group: L, Inhibitors of photosynthesis at photosystem I (PSI inhibitors)
Resistance risk: Moderate

Flumioxazin 15 grams /tablet (Clipper herbicide®)
Rate: 1 tablet for every 37.5 cubic metres of water to achieve 400 parts per billion.
Comments: For use on dense or established weed populations in enclosed water bodies, deeper than 0.5 m and larger than 37.5 cubic metres, or margins of larger, still water bodies. Throw tablets directly into the water to achieve uniform distribution of the herbicide. See label for further instructions and restrictions.
Withholding period: 14 days before using treated water to irrigate food crops. See label for withholding periods for other uses of treated water.
Herbicide group: G, Inhibitors of protoporphyrinogen oxidase (PPOs)
Resistance risk: Moderate

Flumioxazin 15 grams /tablet (Clipper herbicide®)
Rate: Inject solution into water body. 1 tablet per 37.5 cubic metres. Each tablet dissolved in at least 20L of water + 0.5-1.0% adjuvant/surfactant
Comments: For use on dense or established weeds in water bodies less than 0.5 m deep or with a volume less than 37.5 cubic metres. Dissolve tablets in water (at least 20 L per tablet) mix thoroughly and then inject the solution directly into the water body.
Withholding period: 14 days before using treated water to irrigate food crops. See label for withholding periods for other uses of treated water.
Herbicide group: G, Inhibitors of protoporphyrinogen oxidase (PPOs)
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 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 West Regional Recommended Measure* (for Regional Priority - Prevention)
Land managers should mitigate the risk of new weeds being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. The plant should not be bought, sold, grown, carried or released into the environment. Notify local control authority if found.
*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.
For further information call the NSW DPI Biosecurity Helpline on 1800 680 244 or send an email to weeds@dpi.nsw.gov.au

Reviewed 2021