The timing of fruit tree harvests are relatively predictable. The fruit season in Victoria tends to start with mulberries and loquats in late November. This gives way to stone fruit in mid to late summer. In late summer pome fruit (apples and pears) begin ripening. In autumn and early winter persimmons, feijoas begin ripening. Citrus provide plenty of tasty options in winter.
As you can see from the chart below, with careful fruit tree selection you should be able to harvest fruit directly from trees for 9 months of the year. Storage of late season apples, plus some citrus should ensure that you can supply your household with fresh fruit for the whole year. I estimate that 10 fruit trees as the minimum number to achieve this.
It is important to recognise that within the individual fruit types, that there are many varieties available. Those varieties may be early, mid or late season varieties. Each variety will generally produce ripe fruit over a four week window (some less, some much more). Consider the time of ripening of the specific fruit variety when planning a backyard orchard. An example of this, is with the group of apples:
Gravenstein apple ripens in January (early)
Golden Delicious apple ripens in April (mid)
Sundowner apple ripens in June (late)
You can review lists of early, mid and late varieties for many different fruit types at the end of the article. In the chart below, I have indicated the mid season varieties as a darker colour than the early and late season varieties on either side. By combining the lists at the end, with the chart below you can come up with a variety list and plan that suits the requirements of your household.