Parrot's feather (Myriophyllum aquaticum)
Also known as:
Brazilian water-milfoil
Parrot's feather is a feathery water weed that grows in and above water. It outcompetes native plants, reducing food and habitat for fish and other native animals.
Profile
How does this weed affect you?
Parrot's feather is a water weed that:
- reduces water quality
- outcompetes native plants
- reduces food and habitat for fish and other native aquatic animals
- invades rice fields, reducing crop yields
- slows or blocks water flow
- can block intakes of pumps and metering devices
- restricts recreational use of waterways, including fishing, swimming and boating.
What does it look like?
Parrot's feather is a feathery plant that grows in water and wet areas. Its growth can become very dense and form floating mats on the water.
Leaves are:
- deeply divided into 18-36 segments giving a feather appearance
- blueish or bright green
- toothed and hairless.
Leaves above the water are:
- up to 3.5 cm long and 8 mm wide
- in whorls of 5 or 6 along the stem
- crowded at the tips of the stems.
Leaves below the water are:
- up to 4 cm long and 12 mm wide
- in whorls of 4-6, further apart along the stem.
Flowers are:
- white
- inconspicuous
- grow in the leaf axils (the junction between the stem and the leaves) on emergent stems.
Male and female flowers grow on separate plants. Only female plants have been recorded in Australia, therefore there are no fruit.
Stems are:
- yellowish green
- 4–5 mm in diameter
- up to 2 m long when spreading along the mud or in the water
- up to 50 cm when erect above the water
- hairless.
Roots:
- are fine and thread-like
- grow from lower nodes on the stems.
Similar looking plants
Parrot’s feather looks similar to these aquatic weeds:
- Eurasian water milfoil (Myriophyllum spicatum), which is prohibited matter in NSW. It has no emergent leaves and the submerged leaves are olive-green.
- Cabomba (Cabomba caroliniana) which is mostly submerged. Sometimes it has a few leaves floating on the surface but no leaves rising out of the water. The leaves are fan-shaped and opposite.
- Ambulias (Limnophila spp.), which has broad leaves above the water and the flowers are blue, white, pink, or lavender.
Some native water plants look similar to parrot’s feather including:
- Red water milfoil (Myriophyllum verrucosum), which has green to reddish purple leaves usually arranged in whorls of 2-4. The leaves are only divided into 12 segments.
- Common water milfoil (Myriophyllum papillosum), which has very thin undivided leaves.
Where is it found?
In NSW, most plants are found in the North Coast, Hunter, Greater Sydney and South East regions.
It is native to South America. It was introduced as an ornamental water plant.
What type of environment does it grow in?
Parrot's feather mostly grows in tropical, sub-tropical and warm temperate climates. It can survive in cold climates, where the plants remain dormant even if the water surface freezes. Parrot's feather grows well in nutrient-enriched water, in still or slow-moving freshwater bodies. It can also grow in saturated mud and gravel next to water bodies, including drains and channels.
How does it spread?
By plant parts
Parrot’s feather can grow from plant fragments. These can be spread by moving water, attaching to boats, trailers or other recreational water equipment. They can also be spread by people dumping aquarium or pond plants.
Male and female flowers are produced on separate plants. Only female plants have been found in Australia, therefore seeds are not produced. If male plants were introduced to Australia, this species could become more prolific.
References
Champion, P.D. Burnett, D. A. & Petroeschevsky, A. (2008). Risk assessment of tradeable aquatic plant species in Australia. NSW DPI.
Identic Pty Ltd. and Lucid (2016). Environmental Weeds of Australia Fact sheet: Myriophyllum aquaticum (Vell.) Verdc. Retrieved: 27 August 2025 from: https://keyserver.lucidcentral.org/weeds/data/media/Html/myriophyllum_aquaticum.htm
NSW DPI (2023). Recognising water weeds: plant identification guide. Second Edition. Regional New South Wales.
Parsons, W.T., & Cuthbertson, E. G. (2001). Noxious weeds of Australia. CSIRO publishing.
PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 27 August 2025 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Myriophyllum~aquaticum
Sainty, G. R., & Jacobs, S. W. (2003). Waterplants in Australia (No. Ed. 4). Sainty and Associates Pty Ltd.
VicFlora (2025). Flora of Victoria, Royal Botanic Gardens Victoria. Retrieved 1 September 2025 from: https://vicflora.rbg.vic.gov.au/flora/taxon/5454fe3f-3590-4549-b9dd-2d3a241449ca
More information
Control
Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth. Using a combination of control methods is usually more successful.
Prevention
To reduce the risk of spreading parrot's feather to new locations:
- Avoid running boat motors or paddling through water plants.
- Check and remove all plant material from boats, canoes, trailers, vehicles, machinery and fishing gear before leaving waterways.
- Prevent nutrient-rich runoff entering infested waterways.
- Never dump unwanted water plants.
Contain infestations wherever possible to avoid further spread resulting from the movement of plant fragments.
Physical removal
Remove as much of the plant material as possible. Contact your local council for advice on how to dispose of this weed.
Draining water body
Draining a waterbody and allowing the parrot's feather to dry out can be an effective control method for small ponds or dams.
Chemical
Only use herbicides registered for use in aquatic situations.
Herbicide options
WARNING - ALWAYS READ THE LABEL
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
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 92971 Expires 31/03/2028
Metsulfuron-methyl 660 g/kg
(Various products)
Rate: 10 g / 100 L water (plus wetter at 200 mL per 100 L)
Comments: Only for enclosed water bodies. Areas within 400 m of potable water supply uptakes are excluded. ONLY apply as a foliar spot spray during non-frost periods using a high volume sprayer/knapsack fitted with calibrated spray equipment. Apply a maximum of 3 applications per year at minimum intervals of 90 days. WARNING: Very toxic to aquatic plants and algae. See permit for more restraints and critical use comments.
Withholding period: Nil (recommended not to graze for 7 days before treatment and for 7 days after treatment to allow adequate chemical uptake in target weeds).
Herbicide group: 2 (previously group B), Inhibition of acetolactate and/or acetohydroxyacid synthase (ALS, AHAS inhibitors)
Resistance risk: High
Dichlobenil 40 g/kg
(Casoron 4G Herbicide)
Rate: 2.9 to 3.9 kg per 10m2
Comments: Exposed soil. DO NOT apply to water which will be used for crop irrigation, for livestock watering, or for human consumption.
Withholding period: Do not graze livestock on treated areas.
Herbicide group: 29 (previously group O), Inhibition of cellulose biosynthesis
Resistance risk: Moderate
Dichlobenil 40 g/kg
(Casoron 4G Herbicide)
Rate: 287 to 388 kg per ha or 2.87 to 3.88 kg per 100m2
Comments: Water less than 1m deep. Apply when weeds are dormant. DO NOT apply to water which will be used for crop irrigation, for livestock watering, or for human consumption.
Withholding period: Do not graze livestock on treated areas.
Herbicide group: 29 (previously group O), Inhibition of cellulose biosynthesis
Resistance risk: Moderate
Dichlobenil 40 g/kg
(Casoron 4G Herbicide)
Rate: 388 to 574 kg per ha or 3.88 to 5.74 kg per 100m2
Comments: Water more than 1 m deep. Apply when weeds are dormant. DO NOT apply to water which will be used for crop irrigation, for livestock watering, or for human consumption.
Withholding period: Do not graze livestock on treated areas.
Herbicide group: 29 (previously group O), Inhibition of cellulose biosynthesis
Resistance risk: Moderate
Biosecurity duty
The content provided here is for information purposes only and is taken from the NSW 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. |
For technical advice and assistance with identification please contact your local council weeds officer.
Reviewed 2025
