Olives originate from the Mediterranean region but have been successfully grown in subtropical regions as well as other temperate parts of the world. It is an extremely hardy tree with an almost legendary drought tolerance. The trees are long lived in optimal conditions and are wind pollinated. Once established seedling trees take about 8 years to bear fruit, and those established from cuttings will be ready in half that time.
- Olives have a shallow root system and can tolerate soils with high lime content as well as sloping sites with shallow rocky soil, but the best crop production will come from far less harsh situations.
- If you have room for an olive grove, you may wish to grow a combination of varieties to improve pollination and yield - that's what commercial growers do.
- The ideal location is one with warm summers and cold winters. In fact, olives have a high cold requirement as much as 1500 hours or more, depending on the variety and this will greatly affect flower production and hence the fruit yield. But be mindful that they also cannot withstand temperatures below minus 10°C.
- The trees will not tolerate waterlogged soils, so good drainage is essential.
- Little is required in the way of fertilisers.
- Plants are normally spaced at about 10 metres apart and pruned to an open vase shape to keep them as low as possible. Subsequent pruning is only to maintain this shape. Heavy pruning may reduce yields and encourage the development of suckers, and so should be avoided.
- Propagation is generally by budding or grafting onto seedling stock, although root grafts, semi hardwood and hardwood cuttings are also successful.
- The only major pest of olives in Australia is brown olive scale. This is not often serious and is easily controlled with horticultural oils. Other possible pests may include weevils and nematodes.
- Diseases include peacock spot fungus and crown gall which is caused by various bacteria. These are usually only occasional problems or localised to particular areas.
Cropping will tend to follow a biennial pattern under good conditions since a heavy crop one year will tend to inhibit flower production in the following year. For this reason, and also to produce good sized fruit, proper thinning is important. Commercial growers may use chemical thinning agents within a few weeks of full bloom to control biennial fruiting. The variety 'Queen' appears to be an exception to this rule.
Olives which are intended to be eaten whole or pickled are best cropped by hand since the fruits tend to bruise if they are removed mechanically. Those intended for oil manufacture can be removed mechanically.
Olive oil can be pressed at home, however it is difficult and you will need a large quantity of olives. To produce 70 litres of olive oil, you will require a half a tonne of olives. You will also need stone or metal rollers to press the olives.
Table olives can be quite easily prepared at home. Firstly, the bitterness of the raw olives must be leached out. One method is to repeatedly wash the olives in an alkaline solution, such as a caustic soda solution. Dissolve 20g of caustic soda per litre of water and cover the olives in this solution. It typically takes about 24 hours for the caustic soda to penetrate the olives to the pit. Rinse the olives in water to remove the bitter taste, changing the water four times daily; this process may take up to 8 days. The olives can then be pickled in a salt solution (brine) made with 80g salt and 60ml vinegar per litre of water. The olives are ready after 2-3 weeks but they can be left in the brine for up to 2 months. When required, remove the olives from the brine, soak in water overnight to remove salt, and consume within 3 days.