where do weeds come from ?

Many of the plants that are now considered to be ‘environmental weeds’ were introduced by early settlers, or by gardeners and farmers who had little or no knowledge of their future impact on the native environment. It is only in recent years that this threat has become apparent.

Weediness is not confined to introductions from overseas. Some Australian native plants, including those introduced from other regions, may impact adversely on the natural environment of another region.

Non-indigenous (that is, not local) species may invade and displace species natural to that area or they may cross pollinate to produce new species which may in time, alter regional biodiversity. Cootamundra Wattle Acacia baileyana is a good example of the former, while many eucalypts are known to interbreed.

Introduced species may sometimes be controlled in a foreign climate by various vectors such as small animals, insects, diseases or climatic conditions such as frost, reducing their potential invasiveness.

To gardeners, farmers or botanists, the term ‘weed’ may mean different things. Pasture weeds reduce the productivity of agricultural land, and may also have negative effects on human and animal health. Environmental weeds cause various problems in natural areas and ecosystems and the cost of control for both farmers and government is estimated at billions of dollars per annum.

It is important to reduce the spread of environmental weeds because...

Better and more effective management of invasive plants will help to reduce the high cost of chemical control, and to reduce the amount of time and energy lost in management of weeds in productive land for food crops, grazing land, cut flowers and forestry. Weed management in public spaces and on natural heritage land is costly, laborious and at times seems overwhelming.