Cabomba

What does it look like?

Cabomba is a submerged aquatic plant that grows rooted in the sediment, but it can also survive floating freely for up to six to eight weeks. It’s a perennial species, meaning it can persist year after year once established.

The plant has two types of leaves. The submerged leaves are the most noticeable and they grow in opposite pairs along the stem (finely divided), giving them a delicate, fan shaped appearance. These leaves are usually a few centimetres long and sit on short stalks.

Cabomba also produces small floating leaves during flowering. These surface leaves are thin and arrow shaped, and the flowers grow from their bases. The flowers are small, white with a yellow centre, and sit just above the water surface.

Cabomba rarely produces seed. Instead, it spreads mainly through fragments of stem and underground rhizomes, which are easily carried by water to new areas.

Why is it a problem?

Cabomba can form dense underwater stands that crowd out native aquatic plants. This changes habitat for fish and invertebrates, reduces water quality, and can significantly alter freshwater ecosystems. Thick growth can also restrict access to lakes, rivers and ponds, making activities like swimming, boating, and fishing more difficult.

Overseas, cabomba is recognised as a highly invasive aquatic weed. If it becomes established more widely in New Zealand, it has the potential to become a serious environmental pest in freshwater systems.

The main ways cabomba spreads are through people. Dumping unwanted aquarium plants, and moving boats, trailers or equipment that are contaminated with plant fragments, can quickly introduce it to new waterways.

Control methods

Do not attempt to undertake control of this species. Please alert our biosecurity team or Ministry of Primary Industries if Cabomba has been observed in freshwater environments anywhere in the region. Take a close-up photo of the plant (if possible), record its location and call the Biosecurity New Zealand Pests and Diseases Hotline – 0800 80 99 66.

If you have Cabomba in an aquarium, double bag the plants and dispose of these at your local landfill or with general household refuse. DO NOT dispose of plants into or near waterways.

More information

Cabomba looks like Hornwort (Ceratophyllum demersum) but differs in that fanwort has leaves arranged in pairs (opposite), whereas the others have leaves arranged in whorls. Fanwort leaves do not have toothed margins, unlike t hornwort.

Cabomba caroliniana is an unwanted organism under the Biosecurity Act 1993. It’s illegal to breed, knowingly communicate, exhibit, multiply, propagate, release, or sell this Unwanted Organism.

Related links

MPI - have you seen this aquatic weed?