The term 'Australia Tree' can be broken down into four crossword solutions: Adelaide (8 letters), EMU (3 letters), Perth (5 letters), and OPAL (4 letters). Adelaide is the capital of South Australia and the fifth-largest city in Australia. The EMU is a large, flightless bird native to Australia. Perth is the capital and largest city of Western Australia. Finally, OPAL is a precious gemstone found in Australia.