Weeds are often grouped in categories depending on their characteristics and impacts, including:
Many weeds occur in more than one category. For example, blackberry is a noxious weed and is also listed as one of Australia's Weeds of National Significance.
The law requires all landholders in certain areas to control certain serious weeds. These are known as noxious weeds, and the law that declares these in NSW is the Noxious Weeds Act 1993.
To be declared noxious, a number of criteria must be met:
Many 'bad' weeds do not meet the criteria for declaration.
Search noxious weed declarations in NSW WeedWise.
For details about the Act, Weed Control Orders and weed control classes see Weeds legislation.
Under the National Weeds Strategy, 32 introduced plants have been identified as Weeds of National Significance (WONS). A list of 20 was endorsed in 1999 and a further 12 were added in 2012.
These weeds are regarded as the worst weeds in Australia because of their invasiveness, potential for spread, and economic and environmental impacts.
View the list of Weeds of National Significance.
More information: Weeds of National Significance (www.environment.gov.au)
Under the National Weeds Strategy, 28 environmental weeds were identified National Environmental Alert Weeds. Alert Weeds are non-native plant species that are in the early stages of establishment and have the potential to become a significant threat to biodiversity if they are not managed.
More information: National Environmental Alert List (www.environment.gov.au)
Freshwater ecosystems are highly vulnerable to invasion by weeds. Many exotic plants have been accidentally or deliberately introduced into waterways in New South Wales, and have become widespread.
View the list of water weeds in NSW.
For more information, including resources and early detection advice see Water weeds in NSW.
Some Australian native plants have become invasive in areas beyond their natural range or habitat. This is partly due to their popularity as ornamental plants, and partly due to landscape changes. Many are not declared in NSW under the Noxious Weeds Act 1993, but are known to be problematic for land managers.
A number of Australian native plants have been declared on Lord Howe Island under the Noxious Weeds Act 1993. These are species that have been introduced to Lord Howe Island that are not part of the endemic island vegetation communities.
A small number of native plants are declared under the Act in other parts of NSW.
Many areas of native vegetation are protected in Australia. Always check native vegetation requirements before undertaking control of a weedy native plant.
View a list of native plants considered weeds in some areas.
All Class 1, 2 and 5 weeds are prohibited from sale in NSW. Some Class 3 and 4 weeds are also prohibited from sale in NSW, either state-wide (some Class 4 weeds) or in some Local Control Authority areas.
Prohibition from sale includes any barter, offer or attempt to sell, receive for sale, have in possession for sale, expose for sale, send, forward or deliver for sale or cause or permit to be sold or offered for sale, or sell for resale.
View the list of non-saleable weeds. For details of where each weed is prohibited from sale, click on the weed name and then select Legal requirements.