T.E.R:R.A.I.N - Taranaki Educational Resource: Research, Analysis and Information Network

Salvinia molesta (Water fern)

Kingdom: Plantae
Division: Pteridophyta
Class: Polypodiopsida/Pteridopsida
Order: Salviniales
Family: Salviniaceae
Genus: Salvinia
Species: S. molesta
Binomial name: Salvinia molesta
Synonym: Salvinia adnata
Common name: Water fern, Giant salvinia, Kariba weed, giant water fern, aquarium water moss

Salvinia molesta is a major, floating, freshwater, aquatic weed fern, native to south-eastern Brazil. Salvinia is a free-floating fern that forms dense mats on water. It does not attach to the soil. It consists of many-branched horizontal stems, 1–2 mm in diameter, which floats just below the water surface. At each node, or joint, on the stem is a pair of floating, green, oval-shaped hairy fronds. A brown frond, consisting of many hairy filaments, also occurs at each node and trails in the water, looking and acting like a root.
The fronds are 0.5–4 cm long and broad, with a bristly surface of numerous distinctive egg-beater-shaped hairs that repel water and assist in floatation. These fronds are produced in pairs also with a third modified root-like frond that hangs in the water. Under the best conditions, plants can form a 60 cm mat. These mats can put a halt to recreational activities on lakes and waterways.
Salvinia molesta prefers to grow in slow-moving waters such as those found in lakes, ponds, streams, ditches, marshes, and rivers. It prefers nutrient-rich waters such as those found in eutrophic water or those polluted by wastewater. It does not usually grow in brackish or salty waters.
Salvinia molesta is often grown as an ornamental plant but it has escaped and become a noxious pest in many regions worldwide.
It is now naturalised in Africa, the Indian Sub-continent, south-eastern Asia, warmer parts of Australia and New Zealand, southern USA and several Pacific islands. It is present in freshwater habitats in upper North Island. If seen please report to your local council.

Thanks to Wikipedia for text and information: https://creativecommons.org/licenses/by-sa/3.0/