About hornwort
Hornwort is a submerged freshwater weed found in still and flowing waters of streams, rivers, lakes, and ponds. It has been found growing to depths of 16 m in clear, deep lakes. Leaves are finely divided, with minute teeth, which make the plant feel rough to the touch. It lacks roots but has modified leaves that anchor the plant in bottom sediments. New plants can form from each piece of the easily broken stems.
Its other common name is coontail.
Why we don't want hornwort in New Zealand
Hornwort rapidly invades water of varying clarity, temperature, light, and nutrient level. Its dense growth habit crowds out native species. It is a major weed in hydroelectric dams, also impeding irrigation, drainage, and other water uses.
Where hornwort has been found
Hornwort is currently widely established in the North Island but is listed as a pest in several North Island Regional Pest Management Plans.
Hornwort has been successfully eradicated in the South Island. It was initially found in Moutere Stream and some private ponds in Motueka, and in Centennial Park Lake in Timaru and the north branch of the Otipua stream. It was declared eradicated from the South Island in 2013.
Find out more about hornwort – Department of Conservation
What to do if you find hornwort
Hornwort is an Unwanted Organism under the Biosecurity Act (1993). Propagation, spread, display, and sale are all prohibited.
If you find hornwort in the North Island, contact your regional council for advice.
If you think you have found hornwort in the South Island, call the MPI pest and disease hotline on freephone 0800 809 966. Do not touch the plants or try to remove them. Leave the plants so they can be treated or removed safely without spreading them further.
