Water poppy (Hydrocleys nymphoides)

Water poppy is a perennial aquatic plant, found in still to slow moving water bodies up to 1 metre deep. It can form dense infestations that choke waterways.

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How does this weed affect you?

Water poppies form dense infestations that can:

• block waterways
• reduce light and oxygen levels in the water
• compete with native water plants
• reduce food and habitat for fish and other aquatic animals
• limit water flow, increasing the risk of floods
• limit access to water for recreational use.

What does it look like?

Water poppy is a perennial water weed with floating and emergent leaves. Stems can be up to several metres long. Leaves, roots and flower stems grow from nodes along the stem.

Leaves are:

• dark green and shiny
• oval, round or heart-shaped
• up to 13.5 cm long and 12 cm wide
• thick and spongy around the midrib 
• in rosettes that either float on the water’s surface or emerge up to 40 cm above the water.

Flowers are:

• pale yellow with a dark brownish-to-purple centre
• 5-8 cm wide
• poppy-like
• cup-shaped with 3 petals
• above the water on stalks up to 30 cm long
• present in warmer months, November to April in warm temperate parts of Australia and from September to April in subtropical regions.

Fruit:

Water poppies have not been known to produce fruit in Australia. In other countries the fruit:

• are a capsule with a beaked tip
• are 15 mm long
• contain several seeds (1 mm in diameter and horseshoe-shaped), which are released when the capsule splits open.

Stems:

• float under the water’s surface
• form tangled, floating mats.

Roots:

• plants can form roots into the mud, usually on the shallower edges of waterways
• grow from the nodes on the stems.

 

Where is it found?

Water poppy is a weed in Queensland, New South Wales and Victoria. In New South Wales water poppy has been found in:

• Murwillumbah and Coffs Harbour on the North Coast
• the Port Hacking river in the Sutherland Shire in Greater Sydney
• the Murray River at Albury in the Murray Region
• Bega in the South East.

It was introduced to Australia as an ornamental pond plant. It is also a weed in New Zealand, South Africa, Fiji, New Caledonia, Japan, England, French Polynesia, and the United States of America.

Water poppy is native to Central and South America.

What type of environment does it grow in?

Water poppy can tolerate both warm temperate and subtropical climates. Plants grow faster in warm locations. And although they tolerate cool conditions they do not tolerate frost.

It is mainly found in still to slow moving water bodies up to 2 metres deep. It grows best in full sun and shallow, nutrient rich waterways but will also grow in shade.

Plants can be found in waterways, lakes, swamps, shallow ponds, drainage channels and farm dams.

Maps and records

• Recorded presence of Water poppy during property inspections (Map: Biosecurity Information System - Weeds, 2017-2024)
  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?

By plant parts

New plants can grow from nodes along the stem. These can break off from the main plant, float to the surface and move to new areas where they take root in the mud. The plants mostly spread at the end of the growing season when nutrient levels are low. Broken stem fragments can be moved by flowing water, machinery and boats.

By seeds

There is no evidence that water poppies have produced fruit or seed in Australia. Plants that grow from seeds have ribbon like young leaves and these types of leaves have not been observed in Australia.

References

Aston H.I. & Jacobs S.W.L. (1980) Hydrocleys nymphoides (Butomaceae) in Australia. Muelleria 4: 285–293[WG1] 

Ford K.A. & Champion P.D. (2020). Alismataceae. In: Wilton, AD (ed.) Flora of New Zealand—Seed Plants. Fascicle 7. Manaaki Whenua Press, Lincoln.

Kodela, P., & Jobson, R. W. (2018). Hydrocleys nymphoides (Alismataceae) naturalised in New South Wales waterways. Telopea, 21, 167-173.

PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 20 June 2022 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Hydrocleys~nymphoides

Sainty, G. R., & Jacobs, S. W. (2003). Waterplants in Australia (No. Ed. 4). Sainty and Associates Pty Ltd.

New Zealand Weed Busters (nd). Water Poppy (Hydrocleys nymphoides) Weed Information Sheet. Retrieved 20 June 2022 from: https://www.weedbusters.org.nz/what-are-weeds/weed-list/water-poppy/

More information

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Control

Successful weed control relies on follow up after the initial efforts. This means looking for and killing regrowth or new seedlings. Using a combination of control methods is usually more successful. Water poppy can be controlled by physical removal or herbicides. It is important to remove all parts of the plant because it can easily regrow from stem fragments.

Prevention

Do not dump aquarium or pond plants into waterways or bushland.

Physical removal

Individual plants and small infestations can be removed by hand. Remove all plants from the soil and water body to stop the plant re-growing and spreading. Check and followup regularly until the plants stop re-growing.

Excavators can be used to remove large infestations. Clean all machinery and remove plant parts before moving off site.

Dispose of all plant parts appropriately.

Disposal

Contact your local council for advice on how to dispose of water poppy.

Chemical control

Larger infestations can be controlled with herbicides. Herbicides can be applied via tablets, injection, spot spraying or a splatter gun. See labels and permits for detailed instructions. Herbicides must be registered for aquatic use.

Herbicide options

See Using herbicides for more information.

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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 actively growing plants. Only those herbicide products that have label approvals in place for aquatic use may be used in aquatic areas. See permit for critical use comments and additional conditions.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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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: Use a splatter gun to spray actively growing plants. Only those herbicide products that have label approvals in place for aquatic use may be used in aquatic areas. See permit for critical use comments and additional conditions.
Withholding period: Nil.
Herbicide group: 9 (previously group M), Inhibition of 5-enolpyruvyl shikimate-3 phosphate synthase (EPSP inhibition)
Resistance risk: Moderate

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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. Alternatively, if weeds grow in clusters, concentrate the tablet application on the densest areas. See label for 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: 14 (previously group G), Inhibition of protoporphyrinogen oxidase (PPO inhibitors)
Resistance risk: Moderate

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Flumioxazin 15 grams /tablet (Clipper herbicide®)
Rate: 1 tablet for every 75 cubic metres of water to achieve 200 parts per billion.
Comments: For use on low density, establishing or re-establishing weeds 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. Alternatively, if weeds grow in clusters, concentrate the tablet application on the densest areas. See label for 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: 14 (previously group G), Inhibition of protoporphyrinogen oxidase (PPO inhibitors)
Resistance risk: Moderate

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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 20 L 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. See label for 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: 14 (previously group G), Inhibition of protoporphyrinogen oxidase (PPO inhibitors)
Resistance risk: Moderate

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Flumioxazin 15 grams /tablet (Clipper herbicide®)
Rate: Inject solution into water body. 1 tablet per 75 cubic metres. Each tablet dissolved in at least 20 L of water + 0.5 - 1.0% adjuvant/surfactant
Comments: For use on low density, establishing or re-establishing 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) and additives in a spray tank, mix thoroughly and then inject the solution directly into the water body. See label for 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: 14 (previously group G), Inhibition of protoporphyrinogen oxidase (PPO inhibitors)
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.
Greater Sydney Hacking River Catchment is classified as the core infestation area. An exclusion zone is established for the rest of the region.	Regional Recommended Measure* (for Regional Priority - Containment) Whole of region: Land managers should mitigate the risk of the plant being introduced to their land. Within exclusion zone: 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. Within core infestation area: Land managers should mitigate spread of the plant from their land. A person should not buy, sell, move, carry or release the plant into the environment.
Murray	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.
Riverina	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. Your local biosecurity weeds officer can help to identify, advise on control, and how to remove this weed.
South East	Regional Recommended Measure* (for Regional Priority - Eradication) 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.
	*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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Reviewed 2024