The National Pest Accord has added 13 new plants to a list of species that are illegal to propagate, distribute or sell.
The accord which has the Ministry for Primary Industries, the Department of Conservation, regional councils and the Nursery and Garden Industry Association as members, was created to help prevent the spread of invasive plant species.
John Sanson from the Ministry for Primary Industries says the list has been reviewed every five years since 2001.
He says the risks associated with the selected plants vary.
Mr Sanson says pipe grass is on the list because it's currently established in some sand dunes in some locations but it has the potential to invade pasture.
He says water hyacinth has been on the list for some time because it can smother water ways, impact water quality and block irrigation systems.
Mr Sanson says one of the plants to be added is drooping sedge which is an issue in a number of waterways in Christchurch.
He says polypody which is also a problem in Christchurch has been banned because it is invading rocky outcrops on the Port Hills.
Mr Sanson says people won't be required to immediately remove plants on the list from their gardens.
But he says gardeners should think about replacing the plants with something that is not such a weed.
The new list of banned plants can be viewed at the website, www.biosecurity.govt.nz/nppa.
