Hymenachne is a semi-aquatic perennial grass that has become a major weed of northern Australia invading freshwater wetlands, flood plains and stream banks.
This plant is a Weed of National Significance
This plant is not to be sold in all or parts of NSW
This plant is a water weed
Hymenachne is a semi-aquatic perennial grass that forms dense infestations in freshwater systems. It has become a major weed of northern Australia where it was originally introduced (to Queensland and the Northern Territory) as fodder for cattle in ponded pasture systems. It has since escaped cultivation and become an unwanted pest of wetlands, flood plains, irrigation systems, water storage facilities and sugar cane crops.
Hymenachne infestations displace native plants, reduce biodiversity and threate native fish populations and wetland habitats.
Native hymenachne (H. acutigluma) is a tropical species that grows in northern Australia and is not considered a problem.
Native to the tropics of South and Central America, hymenachne has been used as a source of dry season fodder for cattle in Venezuela, Mexico and Cuba. It is considered a serious weed in Indonesia, Suriname, Trinidad and the Florida wetlands of USA.
Many infestations occur throughout northern and central Queensland and the Northern Territory, including conservation areas of Kakadu National Park.
In New South Wales (NSW) small, isolated infestations have been found in various locations in the Richmond, Tweed and Clarence River catchments on the North Coast. All known infestations are subject to control programs, with the aim of eradication.
If left undetected, hymenachne has the potential to spread further in northern NSW and become a major weed of wetlands and waterways.
Hymenachne reproduces by seed and broken stem fragments.
Each flower head can produce over 4000 viable seeds, generally in the autumn months as day length decreases. On land, seeds require contact with waterlogged or moist soil for at least 48 hours before germinating. Germination can occur at any time of the year but more commonly from November to March. Seeds can survive in water and are spread during annual flooding events and in mud attached to the fur or hooves of animals. Waterbirds may also be responsible for spreading seed.
Broken stem fragments can be carried to new locations by floodwaters, and then take root in moist soil.
Hymenachne is a perennial grass that prefers swampy or seasonally flooded areas, growing in water up to 2 m deep.
Key identification features
Hymenachne will invade freshwater wetlands, flood plains and stream banks. Hymenachne thrives in nutrient-rich water.
2006 edition prepared by Rachele Osmond; 2013 edition reviewed by Rod Ensbey and edited by Elissa van Oosterhout.
Charleston K (2006) Hymenachne (Hymenachne amplexicaulis) Control methods and case studies, Queensland Department of Natural Resources, Mines and Water
Hosking JR, Sainty GR, Jacobs SWL & Dellow LL (in prep) The Australian WeedBOOK.
Hymenachne is difficult to control and is capable of spreading from plant fragments, requiring strict hygiene procedures during its removal. If you suspect you have found hymenachne, immediately contact a local council weeds officer who will assist with identification, removal and eradication.
See Using herbicides for more information.
PERMIT 13921 Expires 30/06/2022
Glyphosate 360 g/L
(Only products registered for aquatic use)
Rate: 14 L / hectare
Comments: Apply by boom, handgun or knapsack, a maximum of 4 times a year. Refer to permit for further comments.
Withholding period: Nil.
Herbicide group: M, Inhibitors of EPSP synthase
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 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 |
Prohibition on dealings
Must not be imported into the State or sold |
Central West |
Regional Recommended Measure*
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. |
Greater Sydney |
Regional Recommended Measure*
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. |
Hunter |
Regional Recommended Measure*
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. |
North Coast |
Regional Recommended Measure*
Land managers should mitigate the risk of the plant being introduced to their land. The plant should be eradicated from the land and the land kept free of the plant. |
North West |
Regional Recommended Measure*
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 fulfill the general biosecurity duty for this weed click here |
Reviewed 2018