Warning over floating fern

News release
29 May 2019

Salvinia in Adelaide pond May 2019. Photo Susan Ivory

Salvinia in Adelaide pond May 2019. Photo Susan Ivory

Aquarium and pond owners are asked to check for the presence of one of Australia’s worst weeds after a recent find at an Adelaide property. 

Natural Resources Adelaide and Mt Lofty Ranges (AMLR) staff visited the property last week after receiving information that the owner might be selling Salvinia, a fern-like invasive aquatic weed. 

They are now working with the owner — who was not aware that he had a Weed of National Significance in his pond — to ensure all the plants are destroyed. 

Even small pieces of the plant can generate new growth, and Michaela Heinson from Natural Resources AMLR said anyone allowing infested pond or aquarium water to enter the stormwater system could enable the weed to rapidly spread. 

“Salvinia grows quickly to form thick, floating mats of vegetation that can choke waterways,” she said. 

“It hampers the flow of water and affects the aquatic habitat of birds, fish and invertebrates. It blocks light and reduces oxygen levels, leading water to become stagnant. It also provides the ideal conditions for disease-carrying insects to breed.” 

Salvinia (Salvinia molesta), sometimes called Giant Salvinia, floats on still or slow-moving water and under the right conditions can double its weight in a few days.

Salvinia. Photo Colin G Wilson

Salvinia. Photo Colin G Wilson

“There are major infestations in the eastern states and we don’t want that to happen here,” Ms Heinson said. 

“You only have to look online to see that many people sell pond and aquarium plants from their back yards, and some might unwittingly be selling Salvinia. It is illegal to move or sell Salvinia in South Australia and a maximum fine of $50,000 can apply for those caught selling it. 

“Our first preference is to work with people rather than to prosecute them. We want people to be aware of what aquatic plants they are buying, and if they’re not sure we can provide advice and guidance. 

“We understand that people don’t always know what plants they have, so we want to educate the public and work with affected landholders to eradicate this weed so that it can never establish in South Australia.” 

Native to Brazil, Salvinia is declared under the Natural Resources Management Act 2004. When removed from a backyard pond Salvinia can be destroyed by being placed in a plastic bag and left in the sun until completely broken down, then placed in the general waste bin (not with green garden waste). 

Information is available at Natural Resources Centres.

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