Olives and olive oil are staples around the world. Cold pressed olive oil is considered to be one of the healthiest vegetable oils available. But where did the olive begin? How is it cultivated? And how many different kinds of olive trees are there?
Origin of the Olive Tree
Olives have been eaten by humans for more than 6,000 years. It is thought that they were first found in what is now Syria, in the Middle east. They were grown and used in Macedonia, Greece, Crete and Egypt. The Phoenicians helped spread the use of olives to Spain and even into Europe.
Olives are not native to the Americas. But the colonization of the “New World”, Australia and the Pacific islands further spread cultivation of olive trees. Spanish immigrants brought olive trees to Peru, Chile and California, areas where the climate is warm and dry, encouraging the development of olive groves. The first olive groves in Australia are believed to have been planted in 1805 in Parramatta, but during the 1800s, olive trees have been planted in most areas in Australia. Large areas of Australia are the perfect climate for growing olive trees.
Climate, Soil and Rainfall: Growing Olives
Olive trees grow best in areas with short, mild winters and long, warm, dry summers. They usually thrive in growing zones 10, and 11. They do not enjoy freezing conditions, so growers where winter frost is possible might need to protect their trees during unseasonable cold snaps. Yet olive trees, although they are not deciduous, need a bit of winter chill to do their best. Ideal winter temperatures are between 32 degrees Fahrenheit and 54 degrees Fahrenheit are ideal. This will allow the tree to go into a period of dormancy, which will allow flowering when the weather warms in spring. Temperatures that fall below 22 degrees Fahrenheit will kill tender new branches. Lower temperatures can kill the whole tree.
Olive trees are picky about moisture. They need a well-drained soil that will keep them from having wet feet, but they are not ideally suited to desert climates. In drier areas, the orchards might need irrigation to thrive. A nice, sandy loam will do very well, especially in an area with moderate rainfall.
The trees do not require special fertilization, but do profit from having a soil fertility that is similar to a productive garden soil. Ordinary 10-10-10 or 13-13-13 fertilizers can be used to improve soil nutrition.
Varieties of Olive Trees
With these beautiful trees being cultivated around the world, it is only logical that there should be many different varieties. There are hundreds of different kinds of olive tree. The species vary by the location where they are grown, their size, color and the way they are used. Most people know of two kinds of olive: Black and Green.
Olive trees are not grown from seed, but instead from cuttings. The scientific name for olive trees is olea europaea. They were originally shrubs, but with cultivation, grafting and other techniques, they have been bred into trees.
Green olives are simply olives that have been picked early in the growing season. Black olives are ripe olives. As the olives ripen, they progress through a series of colors: Light brown, red, purple and deep, dark black. The darker the olive, the riper it is. Each stage has its own, unique, delicious flavor.
Olive types do not stop with stages of ripening, however. There are hundreds of varieties – far too many to cover in one short article.
Common cultivars can be divided into three main types: olives for oil, olives for table and olives that can be used for both.
Oil types that are frequently grown in Australia include: Mission, Arbequina, Barnea, Pendolino and Picual, just to name a few.
Food, or table type olives grown in Australia include: South Australian Verdale, California Queen, and Sevillano or Queen of Spain.
Olive types grown in Australia that can be used for both oil or food include: Leccino, Kalamata, and Manzanillo.
Differences between the different varieties include features such as size of pit, the overall size of the fruit, time to maturity, hardiness and whether it needs another variety with which to cross pollinate.
Harvesting and Preparing
Olives can be harvested mechanically, but the results are sometimes disappointing as the mechanical pickers do not differentiate between levels of ripeness. Handpicking, while perhaps more expensive in labor, is more likely to produce a reliable yield.
The olive fruit does not come off the tree ready to eat. Olives need to go through a fermentation process to become truly edible. They can be soaked in brine, in plain water, lye, oil or subjected to a sun/air cure, which can include leaving them on the tree for a time. Plain water cure is slow and seldom used. The lye cure was developed in Spain and is very fast but does not produce a very flavorful olive. Brine creates an olive that tastes good. Oil cured olives can become mushy over time. Dry curing produces a wrinkly olive with good flavor.
A Vegetable-like Fruit
Olives are a fruit, but they are not sweet at all. Instead, they are high in oil and in nutrients. There are about 59 calories in one olive, but no sugar at all. Often used as a garnish, olives can help create a feeling of satiation.
On top of that, olives just plain taste good, so it is wonderful to know that over-all, they are actually good for you as long as they are eaten in moderation.