Species: Salvinia molesta

weed identification

common name
Salvinia, Giant Salvinia, Kariba Weeds, Giant Azolla, Watermoss, Water Spangles

Salvinia molesta is a free-floating, mat-forming aquatic fern with three growth stages. Small-leaved S. molesta invades open water during its primary stage. The secondary form is somewhat larger with slightly folded leaves, and the third form is considerably larger with significantly folded and densely packed leaves. Under optimal conditions plants can form a 60cm thick mat.


Salvinia molesta prefers to grow in slow-moving waters such as those found in lakes, ponds, billabongs, slow moving streams, ditches, marshes, and slow moving rivers. It prefers nutrient-rich waters such as those found in eutrophic water or those polluted by waste water.

native or exotic?

Salvinia in Australia does not produce viable spores, and all reproduction is vegetative via bud expansion and breaking of rhizomes.


Human activity, improper disposal of ornamental plants, waterfowl. Once in a waterway, it can be spread by infested boats which not only spread it to new areas, but also break the plant up which allows it to propagate.


There are none in Australia

What does Salvinia look like?

Use these images below to help you decide whether you are dealing with Salvinia.

Disadvantages of Salvinia

Full coverage of a pond or dam by Salvinia can cause significant problems such as:

  • Stopping oxygen diffusion
  • Shades out all submerged vegetation preventing further growth and causing death
  • Causes fish and other aquatic life death
  • Changes the water chemistry to favour harmful algae and bacteria
  • If left untreated, Salvinia can render the water unusable and make treatment far more costly than if initially dealt with


Orange Oil – Designed to treat free floating organic matter. This treatment is best applied when 20% of the surface water is still visible, and is intended to be used over multiple treatments (day 1, 2 and 4).

AQ200 Aquatic Herbicide + Wetting Agent – Chemical Herbicide designed to kill free floating weeds quickly. Use on mild to severe infestations.

Aquatic Weed Skimmers – Physically remove free floating weeds. Use on mild infestations or to aid herbicide treatments.

Aquatic Harvesting – Large amphibious machine that clears the surface of floating aquatic weeds. Book this service for severe infestations or for larger water bodies.

prevention options

Surface Clear – Creates a protection barrier on the surface of the water to limit plant replication and new infestations forming. Use on its own or after herbicide treatments.

Aerating Fountains – Reduces the severity and likelihood of aquatic weed infestations. Use in any body of water.