The first legislation recognising weeds as a problem was enacted by various provincial councils in the 1850s. These were acts or ordinances against individual species or groups of species such as gorse, watercress or thistles. In 1900 the Noxious Weeds Act was passed, followed by several similar acts and the Nassella Tussock Act 1946. In 1950 a new Noxious Weeds Act became law, and successive acts were introduced to meet the changing patterns of the agricultural industry. These were superseded by the Noxious Plants Act 1978.
The Noxious Plants Act has been replaced by the Biosecurity Act 1993, which moved the main responsibility for weed legislation away from central to regional government. Regional councils and unitary authorities must now develop pest management strategies every five years. These apply to current and potential animal and plant threats and to pest control, and may be the responsibility of the land owner or the council, or both, depending on the location and pest species.
The National Plant Pest Accord is an agreement between the Nursery and Garden Industry Association and central and regional government, listing potential problem plants that cannot legally be propagated, distributed or sold anywhere in the country.