Water star grass is a water weed with white to pale blue flowers that can grow both under and above the water. It grows well in warm water and can form dense mats, reducing water quality.
Water star grass forms thick mats on the water's surface that:
Water star grass is a perennial aquatic plant. Plants usually start growing underwater, rooted in the mud. These plants look like star-shaped grass and send out long stems to the water’s surface.
Leaves on underwater plants:
Leaves on floating plants are:
Plants form roots at nodes. They are usually rooted in the mud.
Water star grass looks similar to kidney-leaf mud-plantain (Heteranthera reniformis), which has kidney-shaped leaves and does not have any underwater leaves.
Water star grass grows near Port Macquarie and on the central coast at Morriset. It has not been found anywhere else in Australia.
Water star grass is native to South America.
Water star grass is an aquatic weed that grows in or on still freshwater. It prefers warm water and in shallow water it can form very dense mats. It can grow in wetlands, drains, farm dams and other damp areas.
Plants produce seeds. Spread is most likely caused when pond or aquarium waste is dumped in wetlands and waterways. Seed could also spread by wind, waterflow out of ponds or by animals especially water birds.
Stem fragments can break off adult plants and start new infestations. Broken stem fragments can be moved by floods, birds and sticking to boats, machinery and people.
PlantNET (The NSW Plant Information Network System). Royal Botanic Gardens and Domain Trust, Sydney. Retrieved 02 July 2021 from: https://plantnet.rbgsyd.nsw.gov.au/cgi-bin/NSWfl.pl?page=nswfl&lvl=sp&name=Heteranthera~zosterifolia
Technigrow Australia (2012). WeedWatch - Water star grass (Heteranthera zosterifolia). Retrieved 02 July 2021 from http://www.technigro.com.au/wp-content/uploads/2016/10/52-Water-Stargrass.pdf
Zlatkovic, B. K., & Bogosavljevic, S. S. (2020). Risk analysis of alien plants recorded in thermal waters of Serbia. Weed Research, 60(1), 85-95.
Remove individual plants or small infestations. Take care to remove all roots and stem fragments. Try not to break the stems when removing plants. Contact your local council for advice on how to dispose of these plants.
Larger infestations can be controlled with herbicides. Herbicides can be applied via tablets, injection, spot spraying or a splatter gun. See label for detailed instructions.
Herbicides must be registered for aquatic use.
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
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: G, Inhibitors of protoporphyrinogen oxidase (PPOs)
Resistance risk: Moderate
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: 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 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.
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 75 cubic metres. Each tablet dissolved in at least 20 L of water + 0.5 - 1.0% adjuvant/surfactant
Comments: For use on 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: G, Inhibitors of protoporphyrinogen oxidase (PPOs)
Resistance risk: Moderate
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 |
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. |
Hunter |
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. |
North Coast |
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. |
South East |
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. |
*To see the Regional Strategic Weeds Management Plans containing demonstrated outcomes that fulfil the general biosecurity duty for this weed click here |
Reviewed 2023