On this page:
- Pest plants managed by the NIPR programme
- How you can help
- About the 9 pest plants
- Two successful eradications
Some of the world's worst weeds have made their way to New Zealand. The National Interests Pest Responses (NIPR) programme is working to get rid of or control them. We work with regional councils and the Department of Conservation to stamp out these plants at more than 500 sites across New Zealand. By working together, we will be successful in protecting the mauri of our land and waterways from pests like these.
There are 9 pest plants in the NIPR programme.
- Salvinia or kariba weed (Salvinia molesta)
- Water hyacinth (Eichhornia crassipes or Pontederia crassipes)
- Manchurian wild rice (Zizania latifolia)
- Cape tulip (Moraea flaccida)
- Pyp grass (Ehrharta villosa)
- Phragmites (Phragmites australis)
- Hydrilla (Hydrilla verticillata)
- White bryony (Bryonia cretica ssp dioica)
- Johnson grass (Sorghum halepense)
Why these plants are managed under the programme
These plants were chosen because they could have devastating impacts on our economy, environment, social, and cultural values.
For example, water hyacinth and salvinia can multiply rapidly, clogging waterways, impeding water flow, and blocking out sunlight required for healthy aquatic ecosystems. Water hyacinth is rated the world’s worst aquatic weed by the Food and Agriculture Organisation of the United Nations. It is also in the top 100 of the world’s worst invasive species across all types of plant and animal pests (Global Invasive Species Database).
The 9 plants in the NIPR programme are hard to eradicate
The ways these plants grow and spread can make it hard to get rid of them completely.
The seeds and rhizomes (underground stems) of some of these plants can lay dormant for up to 20 years. That means we need to continue to monitor sites and look for new growth for many years after the last plant has been removed. It's only after this time we can declare it eradicated.
Some of these plants grow in, on, or around water, on cliffs, and on remote islands. People working on the programme often need to use boats, helicopters, abseilers, sniffer dogs, and specialist equipment to access, find, and remove plants.
Water hyacinth seeds and fragments are easily spread by water, wind, and machinery. It spreads rapidly – 25 plants can form a one-hectare mat in a single growing season. Salvinia also grows fast – it can double in size in 8 days.
Banned: Water hyacinth and salvinia
Do not use them in aquariums or ponds
While water hyacinth and salvinia may look like good options for aquariums or garden ponds, they are serious pests. They are banned from sale, distribution, and propagation in New Zealand. Despite this, some people continue to illegally propagate and sell these plants or drop them in streams, ponds, and wetlands. This can undo many years of hard work to get rid of these plants.
All the plants managed under the NIPR programme are banned from sale, distribution, and propagation in New Zealand.
It takes all of us to protect what we’ve got. You can help by keeping an eye out for these 9 pest plants. These plants are all Notifiable Organisms under the Biosecurity Act 1993. If you think you see one, you must report it by calling the pest and disease hotline on freephone 0800 80 99 66.