Cabomba is a declared weed throughout Australia.

Cabomba: a fast-growing submerged aquatic weed

There is currently no effective method for controlling cabomba once it becomes established in Australian aquatic habitats.

• 2 November 2006 | Updated 14 October 2011

• Background
• The problem

Background

Cabomba (Cabomba caroliniana), or water fanwort, is a fast-growing submerged aquatic weed that has the potential to spread throughout aquatic habitats of Australia. It grows well in slow-moving water bodies, particularly where nutrient concentrations are high.

Cabomba prefers areas of permanent standing water less than three metres deep and is often found along the margins of lakes and reservoirs. However, it can grow in deeper water.

Cabomba is easily recognised by its finely dissected underwater leaves that are feathery or fan-like in appearance. 

Flowers are small, approximately two centimetres in diameter with six white petals and yellow centres. They often extend above the water surface, making weed infestations more visible during the summer months.

Submerged leaves of hornwort (Ceratophyllum demersum) and water milfoil (Myriophyllum species) may be confused with cabomba leaves, however neither of these plants produce the showy emergent flowers of cabomba.

Cabomba originates from South America and was introduced to Australia through the aquarium trade.

The problem

Cabomba was accidentally introduced into lakes and streams through the dumping of aquarium water and on purpose to enable cultivation for later collection and sale. 

The plant's tolerance of fragmentation and ease of cultivation make it a desirable aquarium plant as almost any fragment can grow into a new plant.

Cabomba is primarily found in rivers and dams of coastal Queensland and New South Wales. Isolated populations also occur from Darwin in the Northern territory to Victoria.

Cabomba is a declared weed throughout Australia and it is illegal to propagate, move or sell this noxious plant. It is easily spread across drainages on water craft, boat trailers and perhaps by waterfowl.

Cabomba negatively effects:

• recreational activities
• aquatic environments
• public safety
• water quality.

Cabomba may reduce germination of desirable native emergent plants and smother native submerged plants including:

• pondweeds (Potamogeton species)
• stoneworts (Chara species)
• hornwort (Ceratophyllum demersum)
• water nymph (Najas tenuifolia).

Alteration of native flora has led to reduced populations of platypus and water rats in northern Queensland. In southern Queensland, cabomba appears to negatively effect populations of the endangered Mary River cod.

Cabomba flowers often extend above the water surface, making infestations more visible.

Cabomba can smother native aquatic plants.

Many recreational activities are less desirable in areas infested with cabomba leading to decreased tourism as the long stems can:

• impede the movement of boats
• get tangled in propellers, paddles and fishing lines
• pose a danger to swimmers who may become entangled.

Infestations also decrease water quality for human consumption by tainting and discolouring potable water supplies. Cabomba also interferes with dam machinery, including valves, pumps and aerators, which increase maintenance costs.

Learn about CSIRO research on the Biological control of cabomba.