Weeds are plants that cause problems. They cause problems for farmers, for gardeners, for public utilities and for conservation.

Many weeds are little more than a nuisance, while others can cause serious losses to crop and livestock production, threaten ecological communities and harm the health of people.

The term ‘noxious weed’ is a descriptive title for a legal definition. This may lead to some misunderstanding. Noxious weeds are more than just ‘really bad weeds’.

Weeds declared noxious have a range of characteristics. As well as the potential to cause harm to community and individual interests, they will be controllable by reasonable means but most importantly, they will be likely to spread within an area and to other areas.

This Primefact covers the following topics:

• Externalities and weed spread
• Why don’t landholders sort out their own problems with spreading weeds?
• What is the economic effect of noxious weeds?
• Many of the weeds that cause the biggest problems are not noxious. Why not?
• Further information