3 days ago
Warning over 'serious aquatic invader' posing a major threat in Aussie state
Aussies have been urged to do their part and be on the lookout for an invasive weed that 'poses a major threat' to the country's waterways and native ecosystems.
Water lettuce — a free-floating plant that grows and spreads rapidly — is a 'serious aquatic invader', Biosecurity Queensland warned this week. While its origins are unknown, the weed can be found in various tropical countries and was introduced to Australia as an aquarium and garden pond plant.
However, it has since become a significant problem in NSW and eastern Queensland, where it can be found in several areas as a result of flooding and abandonment.
What is water lettuce?
As its name suggests, the weed resembles a small, floating, open head of lettuce, however, despite its appearance, it's not edible. The plant features pale green fan-shaped, hairy leaves, small pale white to green flowers and egg-shaped fruit that contain seeds.
Water lettuce (pistia stratiotes) prefers stationary or slow-moving streams with high nutrient concentrations.
Why is water lettuce a problem?
The species, which sees a spike in growth as temperatures warm up in spring, can form dense mats that cover rivers, wetlands, dams, reservoirs and irrigation canals, restricting water flow and creating a breeding ground for mosquitoes, biosecurity authorities told Yahoo News.
The swathes of plants can also prevent light penetration and exchange of gasses, leading to a drop in oxygen in the water, and therefore damaging native ecosystems and wildlife habitats. Each one can generate several daughter plants, which helps its rapid spread, along with seeds and water movement.
In Queensland, water lettuce is regarded as a category three restricted invasive plant under the Biosecurity Act 2014, and it is illegal to keep, give away or release into the environment. However, not everyone appears to be aware of that fact, prompting authorities to issue an alert online.
'Some people keep it as an ornamental and offer it for sale as a pond plant on social media,' a Department of Primary Industries spokesperson told Yahoo. 'This increases the risk of spread, particularly into other states where water lettuce is not an established invasive species.'
Queensland residents who find the weed on their property are obligated to take practical steps to minimise its spread. Water lettuce is also considered to be a weed in NSW and a declared pest in WA.
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How do I remove water lettuce?
The invasive weed can be removed by hand if it is found in small numbers. Herbicides are often the only practical method for larger infestations, and spraying results in a quicker death in the warmer months.
For more information or advice, contact your local government.
'One of the world's worst weeds' found in Aussie city for first time
Water lettuce isn't the only aquatic invader causing issues in Australia. Earlier this year, authorities in the Top End sounded the alarm after 'one of the world's worst weeds' was discovered in the region for the very first recorded time.
Authorities attended a Darwin property in June after receiving a tip about a suspicious plant being offered online. There, they took samples of the plant from a contained garden pond which was later confirmed to be Amazon frogbit, an invasive weed that is also capable of choking waterways.
'The property owner was unaware they had Amazon frogbit and we are thankful a member of the public familiar with such weeds brought this to our attention,' a Department of Lands, Planning and Environment spokesperson told Yahoo News at the time.
'The owner informed us that he did not know where the frogbit had come from and stated that it had appeared in the pond around three months ago during the 2025 wet season.'
While the weed is considered a pest in some local government areas in Queensland, it is not actually prohibited in the state and can even be purchased. However, south of the border it's a different story. In NSW it is illegal to buy, sell, trade or move it into the state, with on-the-spot fines as high as $2,000 for anyone caught doing so.
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