Michael North & The Layman’s Guide to the Cultivation & Care of the Greek Olive Tree (and others)

The olive tree produces more olives every other year; this cycle is repeated throughout the life of the tree.

From seed, the first seven years is mostly unproductive. Seven to thirty years the tree grows with a constant increase in productivity. From thirty-five to one hundred and fifty the tree reaches maturity and is in full production. At one hundred and fifty years, the olive tree starts aging with a remarkable productivity for centuries, and sometimes for over a thousand years or more!

The olive tree is very robust. It can endure temperatures below 6-7°C (21-23°F) in the winter and long periods of drought in the summer. It grows best in areas with low rainfall; say an average of 14?-16? per year, and a dry summer with temperatures of above 40°C (104°F). i.e. in a Mediterranean type climate with a hot dry summer, and a cool wet winter.

A typical year in the life of the olive tree:

Spring
In the spring the tree starts to blossom after a rest period during the cold months of winter. The soil around the tree must be fertilized and tilled for the improved storage of water near to the roots. In the spring fertilizing provides the minerals and other necessary substances for the blossoming. It is estimated that 48kgs. (100lbs.) of olives remove from the soil an average of 40g (14.3oz) of nitrogen, 91g (3.2oz) of phosphoric dioxide and 45g (1.6oz) of potassium. An old and effective treatment is the use of organic fertilizers (dung, green fertilizer, etc.) that can supply nitrogen, phosphorus, potassium and many other microelements.

Summer
In the summer months, the olive tree survives in a dry climate. In fact, a great number of trees (especially those up in the mountains) are not watered during the summer months because water is not available in these areas. However, for trees that are located on flat land near the sea, an adequate water supply is essential at certain times of their vegetative cycle. These trees are watered every two to three weeks during the summer months when the fruit is in its early stages of growth and the pits harden. The fruit continues to grow until the moment when the green color of the skin fades and reddish spots appear. During these stages a lack of water may cause the fruit to be smaller, its oil content lower, and it may even cause the fruit to fall from the tree. In this period olives can be damaged due to exposure to harsh weather, disease and parasites. A very good harvest might be seriously jeopardized by these factors. The Olive Fly (Dacus Olei) is the most feared enemy. In certain years this insect can destroy the entire crop. It is found in many olive-producing areas in the world. The larvae causes premature fruit drop and yield reduction. An infestation seriously affects oil volume, alters its color and increases acidity – the enemy to some palates! Farmers use against the fly antiphrastic, poisoned bait, and certain parasites of the olive fly that attack its larvae during summer.
Autumn/Fall
The olives grow ripe and lose their green color due increase in oil content, and reduction in water content. A critical period, the growth and ripening of the fruit require a constant supply of minerals and other substances. Lack of water and nutrients during autumn vegetation can seriously affect the year’s crop as well as the tree's productivity in the following year. The soil surrounding the plant is treated at a maximum depth of 20cm (7.8 in) in order to avoid damaging surface roots. This treatment allows the mixing of fertilizer with the soil and prepares the soil to receive rainwater and to maintain humidity as long as possible. The simultaneous elimination of infesting weeds helps the plant and prepares it for harvesting.

Winter
The olives become ripe, their color changes from green to violet, and finally to almost black while their pulp becomes soft. The ripening progress is relatively slow, especially when sunlight is not intense. Olives are harvested from green through to having dropped on the ground black – although this is a matter of individual choice, and/or the application of the grower. However, the oil content will start to decrease when fully ripened. The tree must be pruned before the onset of spring. The goal of pruning is to increase productivity, and to give a well-balanced growth to the tree throughout the coming year.

Olive groves require care throughout the year and the work is labour-intensive. Olive harvesting does not lend itself to mechanization. Almost all operations are manual, which fuels the high prices of olive oil.

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