About salvinia
Salvinia is a perennial freshwater aquatic fern that forms dense floating mats on still and slow- moving water including ponds, streams, rivers and wetlands.
It has close-growing brown-green leaves up to 4 cm long that are folded across the midrib.
The upper surfaces of the leaves are densely covered in water-resistant hairs.
Fine root-like structures hang down into the water, often with chains of small, round, infertile sporocarps.
Salvinia × molesta was previously known as Salvinia molesta but it is now recognised as a hybrid. Salvinia × molesta is commonly known as salvinia, giant salvinia, or Kariba weed.
Why we don't want salvinia in New Zealand
Salvinia is one of the world’s most damaging aquatic weeds. It forms extensive mats that can completely smother waterways and severely affect water quality. It can double in area within 2 weeks in warm conditions (such as in the north of New Zealand) completely covering the water surface and creating a drowning risk for people and animals. It severely affects water quality, smothers or forces out native plants, attracts breeding mosquitoes, removes oxygen from the water, and blocks dams and irrigation systems.
Where salvinia has been found in NZ
Salvinia has been found in many locations in New Zealand in the past, mostly in the warmer areas of the North Island. It's also been found as far south as Christchurch.
Sites vary in size from large wetlands to small domestic garden ponds and aquariums.
Salvinia eradication programme
Salvinia is one of the species being eradicated through the National Interest Pest Responses programme. The eradication programme consists of containing a new infestation at a site to prevent further spread, site treatment (which can be manual removal of plants or herbicide application) and monitoring for 2 to 5 consecutive years after the last plants are detected to ensure no viable plant material remains. It only takes a very small stem segment to start off a new infestation. These segments can survive out of water as long as they remain moist, such as in damp mud or under other vegetation along the banks of a pond or stream.
Biosecurity New Zealand works closely with the regional councils, the Department of Conservation, and other organisations to eradicate salvinia from New Zealand.
National Interest Pest Responses programme
What to do if you find salvinia
Salvinia is an Unwanted Organism under the Biosecurity Act (1993). Propagation, spread, display, and sale are all prohibited. It is also a Notifiable Organism, which means you must report all sightings to the Ministry for Primary Industries (MPI).
If you think you have found salvinia or if you have it in your property:
- freephone our pest and disease hotline on 0800 809 966
- don’t touch the plants or try to remove them
- take photos and leave the plants so they can be treated or removed safely without spreading them further.
- don’t tip the content of your aquarium or pond into a waterway, as this could start another infestation with potentially serious consequences.
What salvinia looks like
