Australia is divided into eight different gardening zones because of the huge variations in temperature and rainfall across this massive continent.
Altitude variations or geographical features within each zone modify temperatures and rainfall patterns, breaking up the eight zones even further.
To complicate the issue, climate change is resulting in evolving milder winter conditions in some areas and longer, harsher winters in others. Last summer, extreme heat or rain events played havoc with a lot of gardens across Australia, and the extent of further changes related to extreme weather events is impossible for anyone to accurately predict.
However, Australia can be divided into three basic gardening or growing zones; Warm, Cool, and Temperate The zone divisions are based on the types of plants that will grow in a moderately irrigated garden in each zone http://aussieorganicgardening.com/?p=298