How do I improve/prepare my soil for planting in Canberra?

Canberra soils generally have a high clay content. Clay can be great for water and nutrient retention but can sometimes impede plant growth because of poor drainage.

The basic idea is to improve (not remove) the soil. The best way to improve clay soil is to use gypsum (clay breaker) and add organic material.

The procedure - if you are planting in a heavy clay soil dig the hole to double the pot size and place the soil next to the hole. In the base of the hole use gypsum at the recommended rate and then combine the existing soil with some organic matter (manure and/or compost and/or high quality garden soil). Mix it all in like a big cake mix. The plant is ready to be planted. 

PS Be a little careful with the amount and type of manure (if any) used when planting native plants. Not all native plants will enjoy manure (or highly enriched composts/soils) in the soil mix.