Salvinia molesta


Also known as:

Kariba weed

Family: Salviniaceae

Origin: South America

Salvinia growing in a lake.
Salvinia covers water surfaces, blocking light to native species.
Photo credit: Sam Happy

Regional Pest Management Plan (RPMP) status

  • National Pest Plant Accord Species
  • Notifiable organism

View more about the RPMP statuses

General description

Perennial free-floating, mat-forming aquatic fern. Stems are branched and hairy. Submerged leaves are finely dissected, root-like and often bear spores. Emergent leaves are either juvenile, small and well-spaced, or mature, < 4 x 5 cm, crowded and folded about the midrib, with eggbeater-shaped hairs on the upper surface.

What you need to know

To help protect our environment:

  • You must not breed, distribute, release or sell salvinia. As salvinia is a National Pest Plant Accord species, these restrictions apply within the Auckland region and across the whole of New Zealand.

If you see salvinia anywhere, you must report it to the Ministry of Primary Industries on 0800 80 99 66.


Disturbed sites, lakes, rivers, streams, ditches, wetlands, reservoirs.


Vegetative spread from plantlets and fragments, dispersed by water, wind, waterfowl and other animals. Human-mediated dispersal through deliberate releases and movement of contaminated boats, aquatic plants and fish.

Impact on environment

Forms extensive mats, outcompeting and displacing native vegetation. Reduces water quality, clogs waterways and creates a drowning risk for humans and animals.


Recommended approaches

Do not attempt to undertake control of this species. The Ministry of Primary Industries will carry out the control of this species.

Salvinia on water surrounded by tall reeds.
Salvinia is a free-floating fern that forms a mat of clustered leaves.
Photo credit: Sam Happy
Tiny leaves of salvinia in a container of soil.
It has an incredible growth rate, doubling in size in as little as eight days. Salvinia spreads by breaking up during water movement sending fragments into other areas.
Photo credit: Holly Cox
Mature salvinia leaves covering a waterway
It grows so quickly that it can block out light to plants that grow on the bottom of a pond.
Partially submerged leaves in pond water
The leaves float above the surface of ponds and lakes.