The concept of a bush garden is to emulate what may have been 200 years ago. However because the landscape has changed since then this concept may need to be modified. For example houses and roads have been constructed. Water courses have been modified. Rainwater has been channelled more directly to the sea. etc.
Probably, therefore, a better definition might be "what would it have been like if these modifications had been in place 200 years ago". This doesn't change much for most sites. However it might be difficult, for example, to develop swamp loving plants where a swamp which once existed had been drained.
The only difference this change makes at Wirrapunga is that a small temporary wetland exists at a point where road water has been diverted. Excess roof runoff from the house is also diverted into this area. The house also provides a shady side that would not have existed 200 years ago.
The biggest compliment I ever received in regard to the design of our bush garden was from a computer person who came to fix my computer. His first words as he came to the house were, "I see you are not much of a gardener."
I would probably spend far more time in my garden than anyone else he knew. Yet he saw it as what it was - a bush garden. Of course he thought bush gardens occurred naturally as they once did but unfortunately no longer.
It is probably the lack of design, the randomness of the bush, which makes it so attractive. I have planted hundreds of thousands of plants. I have always attempted to plant them randomly. I had always failed until I discovered how to do it.
It is simply a matter of allowing nature to do it for you. If an indigenous plant appears in your garden then that is where it grew. That is all there is to it. If you like it there you simply leave it. If you don't like it then you pull it out.
If I want a species of plant in my garden then I collect seeds and spread them. They grow where they grow. If I want more, I wait for them to spread. If I want less I remove some.
Normally I leave fallen trees and twigs where they fall. Sometimes I put them closer together to provide habitat for our wildlife. We have an organic vegetable garden. It is the wildlife that control our garden pests. The birds, lizards, frogs etc. who do this job are attracted and cared for by our bush garden.
It is important to understand that our indigenous wildlife need indigenous vegetation. They also need to have suitable sites so they can repeat their whole life cycle. Only the other day I watched a bearded dragon digging holes to find a suitable site to lay her eggs. After she had selected a siuitable site, laid her eggs and carefully filled in the hole, I marked it so I would not damage the eggs before they hatched. The important point is that I could not have selected a suitable site for her. I need to ensutre there are a few open, sunny, sandy sites for her to choose from.
The design rules for our bush garden are very simple:
Use only indigenous plants;
Allow the plants to choose where they grow;
Remove all non-indigenous plants;
Try to have as many different habitats as possible;
Interfere as little as possible.