Free-Floating Aquatic Weeds have roots that are not attached to substrate and float on the water's surface. The most common Australian Free-Floating Aquatic Weeds are: Duckweed, Azolla, Liverwort, Salvinia, Water Lettuce and Water Soldier.
There are also 3 other types of Aquatic Weeds:
Duckweed
Species: Lemna spp., Wolffia spp., Spirodela spp. Family: Lemnaceae
Distribution
NSW, NT, QLD, SA, TAS, VIC, WA
Description
Duckweed has 1-3 oval shaped leaves, is light-green in colour, nearly flat on both sides and float on or just beneath the water’s surface. Dense growth appears as a green mat on the surface of the water.
Life Cycle
Perennial
Origin
Native
Control Methods
Pacific Azolla / Ferny Azolla
Species: Azolla filiculoides / Azolla pinnata Family: Azollaceae
Distribution
NSW, NT, QLD, SA, TAS, VIC, WA
Description
Fern-like appearance, from 1-2.5cm in diameter and often with roots. Older plants in full sunlight are reddish, whereas plants in shade are greenish.
Life Cycle
Perennial
Origin
Native
Control Methods
Liverwort
Species: Ricciocarpus natans Family: Ricciaceae
Distribution
NSW, TAS, VIC, QLD
Description
Green with blackish outer edges. Appearance of leaf growing side-by-side or divided into two. Underside leaf bears purplish scales. Often found floating with Duckweeds on still water.
Life Cycle
Perennial/Annual
Origin
Native
Control Methods
Salvinia
Species: Salvinia molesta Family: Salviniaceae
Distribution
NSW, NT, QLD, SA, VIC, WA
Description
Has floating leaves covered with tiny hairs which makes the weed waterproof. Has been known to double its size extremely quickly in as little as 5-10 days. Prefers to grow in slow moving water bodies, Can spread through water fowl. Is a threat to biodiversity, including fish, insects or any plants underneath its mat.
Life Cycle
Perennial
Origin
Introduced
Control Methods
Water Lettuce
Species: Pistia stratiotes Family: Araceae
Distribution
NSW, NT, QLD
Description
Also known as water cabbage. It can completely cover water bodies, reducing oxygen, killing fish & attracting mosquitos. Up to 15cm tall and 30 cm wide. Reproduces rapidly by offshoots. Occurs in slow moving waterways in tropical and subtropical warmer temperate regions.
Life Cycle
Perennial
Origin
Native (NT) Introduced (NSW & QLD)
Control Methods
Water Soldier
Species: Stratiotes aloides Family: Hydrocharitaceae
Distribution
None at present
Description
Whole plant similar to a pineapple top. Native to Europe, not yet recorded in Australia. If encountered, notify authorities.
Life Cycle
Perennial
Origin
Introduced
Control Methods