A weed is any plant growing where it is not wanted. Most people think of bindiis and other garden pests when they think of weeds, but weeds occur in many other places and forms as well. In fact, some of the plants deliberately grown in gardens can be serious weeds in other places. Weeds are found in crops and pastures, on roadsides, in creek banks, in bushland and many other places, where they can cause a great deal of damage. Weed invasion is one of the most serious and expensive land degradation problems in Australia.
Some weeds are plants that have been brought from other countries.
Others come from within Australia. Weeds can come in any shape and size and can be any type of plant. For example, trees, shrubs, vines, annuals or water plants. Sources may include, school library, family libraries, local community library, groups such as Greening Australia, nurseries. Some students may have a degree of knowledge regarding native or introduced flora because of exposure to this by parents or neighbours.