Anchored water hyacinth (Eichhornia azurea)

Anchored water hyacinth is a water weed that can float or grow under the water’s surface. It forms dense mats in, and across water bodies.

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How does this weed affect you?

Anchored water hyacinth invades still or slow-moving freshwater bodies. It forms dense mats in and across the top of the water where it:

• obstructs irrigation channels
• causes water losses by increasing transpiration
• smothers native plants
• reduces food and habitat for fish and other aquatic animals
• reduces access for recreational activities such as swimming and boating
• harbours mosquitoes.

What does it look like?

Anchored water hyacinth is usually rooted in soil under the water but can also be free floating. The leaves may be underwater, floating or above the water.

Leaves:

Leaves growing above the water are:

• green
• often round but can vary in shape
• 5–16 cm long and 2–16 cm wide.

Leaves growing underwater or in heavy shade are:

• green
• elongated
• 6–20 cm long and 1 cm wide.

Flowers are:

• mostly white or lavender-blue with deep purple centres and a distinct yellow spot on the top petal
• funnel-shaped with 6 toothed petals 1–3 cm long 
• clustered along an erect hairy spike 8–12 cm above water
• open for only one day
• present in summer and autumn. 

Fruit:

• are a capsule 1 cm in diameter
• usually contain 10–13 seeds that are 1–2 mm long.

Stems:

• underwater stems are smooth and branched.

Similar looking plants

Anchored water hyacinth looks similar to:

• Water hyacinth (Eichhornia crassipes), which is also a weed and does grow in NSW. It has bulbous (swollen) leaf stalks and its petals do not have serrated edges. 
• Monochoria cyanea - a native subtropical plant occassionally found in NSW. It has smaller flowers, with no yellow spot on the petals. The emergent leaves are more elongated and have a pointed tip.

Where is it found?

Anchored water hyacinth is not currently known to occur in Australia. In 2005 it was removed from a retail outlet in northern Sydney and has not been reported since. 

Anchored water hyacinth is native to Mexico, Central America, South America and Jamaica.

What type of environment does it grow in?

Anchored water hyacinth grows in still or slow-moving freshwater such as wetlands, dams, irrigation channels and river banks. It usually has roots in mud or clay beneath the water. It can reach the surface even when rooted at depths of up to 10–15 metres. It can also survive free-floating in the water.

Maps and records

• Recorded presence of Anchored water hyacinth 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?

By seed

Flowering occurs in summer and autumn and seeds germinate in spring. Seeds are spread in water and mud via vehicles, boats and birds.  

By plant parts

Anchored water hyacinth is able to reproduce vegetatively when new daughter plants grow from the stems of the parent plant. It spreads when daughter plants or pieces of stem break away and move downstream. Whole sections of an infestation can break off and move during floods and periods of high water flow.

It could be spread by dumping unwanted pond or aquarium plants.

References

Burton, J. (2005) Water hyacinth Eichhornia crassipes. Agfact. P7.6.43 third edition. NSW DPI.

Department of the Environment (2011) Weeds in Australia, Eichhornia azura, Australian Government. Available at www.environment.gov.au

Grantley, J., McPhersonm, F., & Petroeschevsky, A. (2009). Recognising water weeds: plant identification guide. Industry & Investment NSW.

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Control

Please do not attempt to treat or dispose of this weed yourself. Report this plant if you see it anywhere in NSW by calling the helpline listed at the top of this page immediately.

NSW DPI will lead an initial response for the treatment and disposal of the plant to stop it from spreading.

Early detection

Early detection of anchored water hyacinth is critical to keeping Australia free of this serious weed.

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: Up to 200 mL per 10 L of water
Comments: Spot spray application.
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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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.
All of NSW	Prohibited Matter A person who deals with prohibited matter or a carrier of prohibited matter is guilty of an offence. A person who becomes aware of or suspects the presence of prohibited matter must immediately notify the Department of Primary Industries

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Reviewed 2021