Which is the only Australian state that has a capital city named after a tree?

The correct answer is Queensland, as its capital city is Brisbane, which is named after Sir Thomas Brisbane. The name Brisbane, however, is often associated with the native 'Moreton Bay Fig' tree, which is prominent in the region and has cultural significance. This unique connection makes it distinct when relating capital cities to trees.

While other Australian states have capital cities, none of them are directly named after a tree in the same way. For instance, Melbourne, the capital of Victoria, is named after a British Prime Minister. Perth, the capital of Western Australia, is named after Perth in Scotland. Adelaide, the capital of South Australia, is named after Queen Adelaide, the consort of King William IV. These names do not have direct associations with trees like Brisbane does with the Moreton Bay Fig.