If you are thinking about apples you will need to work out the variety and size before you buy. You will need two plants in order to ensure that the flowers are fertilised.
Apples grow best in colder climates, as they rely on a consistent cold spell to form fruit. If you are buying your trees from a nursery they will come bare-rooted and dormant (looks like a dead stick with a root ball at the end).
Plant the trees in winter, in a sunny position. The soil doesn’t need any particular preparation; just give it a good forking over to loosen it up. Water well but don’t fertilise the dormant plant (waste of time and money).
Apple trees can be grown in lines (like an orchard), or espaliered on a trellis or wall, or planted in individual beds. Plant trees at least 3 to 4 metres apart depending on the size tree you have bought.
Prune trees in winter, when they are dormant. Use this time to trim and shape the tree if you so desire. Fertilise the plants in spring when the first sign of growth appears. Make sure that you water them well throughout the warmer months.
A grafted tree will fruit within a year. The biggest threat to your fruit will be from possums, which are more than happy to eat the apples while they’re still green. Investing in a good quality net is recommended.