If I had a dollar for every BBQ joint in America with "Hickory" in the name, I could retire. Hickory trees grow abundantly in a wide swath that runs from the East Coast (Virginia, North Cackalackie, South Cackalackie & Georgia) though about central Nebraska, Kansas, Oklahoma and Northern Texas. I'm sure there's some on the West Coast and elsewhere, I'll bet Richtee will tell me hickory can be found up his way too.
Oak has good flavor and provides good, consistent heat. It is also prevalent just about everywhere in North America. The joints I grew up eating at in Kansas City mostly used a combination of Hickory and Oak. Dance with the one who brung ya - I have easy access to Hickory and Oak so that's my "go-to" combination. Living in South Carolina now, I have ready access to free peach wood from local orchards. Free is good, and so is peach. I use peach on pork and love it.
On my current visit to the Land of Aus (hey, I grew up in the land of Oz, no Dorthy/Toto jokes please), I've had some really great 'cue done on iron bark and red gum. I think both of these pair really well with beef and especially lamb (have I mentioned that I have become obsessed with BBQ'd Lamb?) Personally, I still think fruit woods pair better with pork, but I wouldn't start a separate fire if I was cooking beef & pork together. To me, the differences in flavor imparted by the choice of wood are fairly subtle. There are a few exceptions, notably mesquite at one extreme, with a very strong, sagey flavor and pecan and alder at the other with very mild flavors.
My eyes have been opened to the world of "spare no expense" barbecue and it is awesome, but my heart will always be with the "soul food", "poor mans kitchen" side of 'cue, the basis of which lies with sourcing reasonably priced local meats and fuel. I would think locally sourced domestic woods like ironbark or red gum would be a damn good place to start in Aus. Alternatively, if you can find a local orchard and offer to pick up some of their deadfall or volunteer to help prune in exchange for the wood, you've got free fuel that will taste even better harvested with your own sweat (ok, not sure that sweating on the wood will do much for the the taste, that was supposed to be more metaphoric).
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