Weed definitions & FAQs
Weeds are often classed in broad groups depending on their characteristics and impacts. The main groups of weeds are
Many weeds can be classified in more than one of these groups. For example, blackberry can be classed as a noxious weed, environmental weed and agricultural weed, depending on its situation and is also listed as one of Australia’s Weeds of National Significance (WONS).
Noxious Weeds
Some serious weeds are required by law to be controlled by all landholders in an area. These are known as noxious weeds and the law that controls these in NSW is the Noxious Weeds Act 1993.
Weeds that are declared noxious are those weeds that have potential to cause harm to the community and individuals, can be controlled by reasonable means and most importantly, have the potential to spread within an area and to other areas.
A weed is declared noxious because its control will provide a benefit to the community over and above the cost of implementing control programs.
Many ‘bad’ weeds do not meet the criteria for declaration. Noxious weeds will have limited distribution with the potential to become more widespread and will cause impact on agriculture, human health or the environment.
In New South Wales the administration of noxious weed control is the responsibility of the Minister for Primary Industries under the Noxious Weeds Act 1993. The Act is implemented and enforced by the Local Control Authority (LCA) for the area, usually local government.
The Act imposes obligations on occupiers of land to control noxious weeds declared for their area.
There are five classes of noxious weeds identified in the Act (see Table 1). All Noxious Weeds in NSW are listed in the Noxious Weeds database.
Table 1 Control classes of noxious weeds
| Control class |
Weed type |
Example control requirements |
|---|---|---|
| Class 1 |
Plants that pose a potentially serious threat to primary production or the environment and are not present in the State or are present only to a limited extent. |
The plant must be eradicated from the land and the land must be kept free of the plant. The weeds are also "notifiable" and a range of restrictions on their sale and movement exist. |
| Class 2 |
Plants that pose a potentially serious threat to primary production or the environment of a region to which the order applies and are not present in the region or are present only to a limited extent. |
The plant must be eradicated from the land and the land must be kept free of the plant. The weeds are also "notifiable" and a range of restrictions on their sale and movement exist. |
| Class 3 |
Plants that pose a potentially serious threat to primary production or the environment of a region to which the order applies, are not widely distributed in the area and are likely to spread in the area or to another area. |
The plant must be fully and continuously suppressed and destroyed.* |
| Class 4 |
Plants that pose a potentially serious threat to primary production, the environment or human health, are widely distributed in an area to which the order applies and are likely to spread in the area or to another area. |
The growth of the plant must be managed in a manner that reduces its numbers spread and incidence and continuously inhibits its reproduction* |
| Class 5 |
Plants that are likely, by their sale or the sale of their seeds or movement within the State or an area of the State, to spread in the State or outside the State. |
There are no requirements to control existing plants of Class 5 weeds. However, the weeds are "notifiable" and a range of restrictions on their sale and movement exists. |
NOTE: All Class 1, 2 and 5 weeds are prohibited from sale in NSW.
* In some cases the following wording has also been inserted "the plant may not be sold, propagated or knowingly distributed."
Weeds of National Significance
Under the National Weeds Strategy, 20 introduced plants were identified as Weeds of National Significance (WONS).
These weeds are regarded as the worst weeds in Australia because of their invasiveness, potential for spread, and economic and environmental impacts.
The weeds are:
in April 2012 the following species where added to the list
More information: Weeds of National Significance (www.environment.gov.au)
National Environmental Alert List Weeds
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.
The weeds are:
More information: National Environmental Alert List (www.environment.gov.au)
Water Weeds
Freshwater ecosystems are highly vulnerable to invasion by weeds. Since European settlement many exotic weed species have been accidentally or deliberately introduced into NSW waterways, and have become widespread.
How are water weeds introduced?
Water weeds have been deliberately introduced through the nursery and aquarium plant industry for display in backyard ponds and aquariums. Species such as water hyacinth and cabomba have primarily been spread by humans into our natural waterways.
Boating or fishing in weed infested waterways has also contributed to the spread of water weeds from one site to another. Propellers and anchors can cut plants into fragments and spread them within and between waterbodies. Fragments can spread from an infested waterbody to a weed free waterbody by attaching to watercraft, trailers and fishing equipment. Some weeds can survive considerable time out of water and a single plant fragment can start a new infestation.
What species are pests?
Aquarium and pond weeds cause major problems if allowed to spread. The following species are declared under the NSW Noxious Weeds Act 1993.
Water weeds can:
- Alter dissolved oxygen levels reducing the water quality
- Restrict navigation and recreational activities on waterways
- Damage and block pumping equipment
- Pose a drowning hazard for livestock and recreational swimmers
- Displace native vegetation
What is NSW DPI doing about water weeds?
The NSW government funds a state weed program targeted specifically at water weeds. This program focuses strongly on the 23 water weed species that are declared under the NSW Noxious Weeds Act 1993. This program assists in delivering community education, awareness and extension programs; provides technical support to key stakeholders; and coordinates state strategies for high priority aquatic weeds.
Water weeds are predominantly spread throughout the river systems flowing along the east coast of NSW. Many western flowing river systems are currently free of major weed infestations. It is therefore the key priority of DPI to ensure that these regional river systems remain free of aquatic weeds. In 2010 we have seen 5 new water weed infestations within the Murrumbidgee, Murray and Warrego river networks. It is vital that people report any suspicious water weed infestation to protect the states water resources from weed invasion.
Help stop the spread of water weeds!
Members of the public, including fishers, divers and members of local environmental groups, are often the first to discover a new exotic weed or the fact that an existing weed has spread into a new area. This information can be very valuable in helping to manage weed problems.
You can protect our waterways and native fish by helping to stop the introduction and spread of water weeds into new areas by:
- Preventing unwanted hitchhikers – Inspect and remove any plant fragments from watercraft, trailers and all equipment before leaving a site or launching at a new site.
- Not accessing waterbodies in infested areas and if in an infested area avoid running the engine through weed beds.
For backyard pond owners:
- Prevent accidental escapes – screen outdoor ponds to prevent overflow during heavy rains.
- Source your pond plants from reputable and/or accredited nurseries/sellers.
- Never dump pond plants in the green waste or local water way, dry specimens thoroughly in a sealed bag.
For everybody:
- Keep a lookout for suspected new water weeds in your local waterways.
- Report suspicious water weeds to the local council weeds officer or phone the NSW Weeds Hotline on 1800 680 244 or email weeds@dpi.nsw.gov.au
FAQs
- For answers to frequently asked questions about weed management.