The Olive Tree - Part IV

The Olive (Olea europaea) is a species of small tree in the family Oleaceae, native to the coastal areas of the eastern Mediterranean Basin, from Lebanon and the maritime parts of Turkey and at the south end of the Caspian Sea. Its fruit, the olive, is of major agricultural importance in the Mediterranean region as the source of olive oil.


Description
The olive tree is an evergreen tree or shrub native to the Mediterranean, Asia and parts of Africa. It is short and squat, and rarely exceeds 8–15 meters in height. The silvery green leaves are oblong in shape, measuring 4–10 cm long and 1–3 cm wide. The trunk is typically gnarled and twisted.

The small white flowers, with ten-cleft calyx and corolla, two stamens and bifid stigma, are borne generally on the last year's wood, in racemes springing from the axil of the leaves.

The fruit is a small drupe 1–2.5 cm long, thinner-fleshed and smaller in wild plants than in orchard cultivars. Olives are harvested at the green stage or left to ripen to a rich purple color (black olive). Canned black olives may contain chemicals that turn them black artificially.


History
The olive is one of the plants most cited in recorded literature. In Homer's Odyssey, Odysseus crawls beneath two shoots of olive that grow from a single stock. The Roman poet, Horace mentions it in reference to his own diet, which he describes as very simple: "As for me, olives, endives, and smooth mallows provide sustenance.Lord Monboddo comments on the olive in 1779 as one of the foods preferred by the ancients and as one of the most perfect foods.

The leafy branches of the olive tree - the olive leaf as a symbol of abundance, glory and peace - were used to crown the victors of friendly games and bloody wars. As emblems of benediction and purification, they were also ritually offered to deities and powerful figures; some were even found in Tutankhamen's tomb.

Olive oil has long been considered sacred; it was used to anoint kings and athletes in ancient Greece. It was burnt in the sacred lamps of temples as well as being the "eternal flame" of the original Olympic Games. Victors in these games were crowned with its leaves. Today, it is still used in many religious ceremonies.

According to Greek mythology, the Olive tree, her gift to the people of Attica, won Athena the patronage of the city of Athens over Poseidon. As far back as 3000 BC, olives were grown commercially in Crete; they may have been the source of the wealth of the Minoan Civilization.

The olive tree and olives are mentioned over 30 times in the Bible, in both the New and Old Testaments. It is one of the first plants mentioned in the Bible, and one of the most significant. For example, it was an olive branch that a dove brought back to Noah to demonstrate that the flood was over. The Mount of Olives east of Jerusalem is mentioned several times. The olive tree itself, as well as olive oil and olives, play an important role in the Bible.

The olive tree made its appearance in the Mediterranean region thousands of years ago and spread to nearby countries from there. The ancient Greeks used to smear olive oil on their bodies and hair as a matter of grooming and good health. Over the years, the olive has been the symbol of peace, wisdom, glory, fertility, power and pureness. Many Greek and Roman writings refer to the olive and its beneficial role. It is estimated the cultivation of the olive commenced more than 7000 years ago. The Russians also helped to spread the olive throughout its extensive empire.

After the 16th century, the Europeans brought the olive to the New World, and its cultivation began in California, Mexico, Peru, Chile and Argentina. It is estimated that there are about 800 million olive trees in the world today, and the vast majority of these are found in Mediterranean countries.

Old Olive Trees
Pliny the Elder told of a sacred Greek olive tree that was 1600 years old. Several trees in the Garden of Gethsemane (from the Hebrew words "gat shemanim" or olive press) in Jerusalem are claimed to date back to the time of Jesus. Some Italian olive trees are believed to date back to Roman times, although identifying progenitor trees in ancient sources is difficult.

One olive tree in Bar, Montenegro, is claimed to be over 2000 years old.

The age of an olive tree in Crete, claimed to be over 2,000 years old, has been determined on the basis of tree ring analysis. Another well-known olive tree on the island of Brijuni (Brioni), Istria in Croatia, has been calculated to be about 1,600 years old. It still gives fruit (about 30 kg per year), which is made into top quality olive oil.

A tree located in Santu Baltolu di Carana in Sardinia, Italy, named with respect as the Ozzastru by the inhabitants of the region, is claimed to be 3000 to 4000 years old according to different studies. In the same natural garden, a few other millenarian trees can be admired.


Cultivation & Uses
The olive tree has been cultivated since ancient times as a source of olive oil, fine wood, olive leaf, and olives for consumption. The naturally bitter fruit is typically subjected to fermentation or cured with lye or brine to make it more palatable.

Green olives and black olives are washed thoroughly in water to remove oleuropein, a bitter carbohydrate. Sometimes they are also soaked in a solution of food grade sodium hydroxide in order to accelerate the process.

Green olives are allowed to ferment before being packed in a brine solution. American black "California" olives are not fermented, which is why they taste milder than green olives.

It is not known when olives were first cultivated for harvest. Among the earliest evidence for the domestication of olives comes from the Chalcolithic Period archaeological site of Teleilat Ghassul in what is today modern Jordan.

Farmers in ancient times believed olive trees would not grow well if planted more than a short distance from the sea; Theophrastus gives 300 stadia (55.6 km) as the limit. Modern experience does not always confirm this, and, though showing a preference for the coast, it has long been grown further inland in some areas with suitable climates, particularly in the southwestern Mediterranean (Iberia, northwest Africa) where winters are mild.

Olives are now cultivated in many regions of the world with Mediterranean climates, such as South Africa, Chile, Australia, the Mediterranean Basin, Lebanon and California and in areas with temperate climates such as New Zealand, under irrigation in the Cuyo region in Argentina which has a desert climate. They are also grown in the Córdoba Province, Argentina, which has a temperate climate with rainy summers and dry winters (Cwa). The climate in Argentina changes the external characteristics of the plant but the fruit keeps its original characteristics.

Considerable research supports the health-giving benefits of consuming olives, olive leaf and olive oil. The olive tree provides leaves, fruit and oil. Olive leaves are used in medicinal teas.

Olives are now being looked at for use as a renewable energy source, using waste produced from the olive plants as an energy source that produces 2.5 times the energy generated by burning the same amount of wood. The smoke released has no negative impact on neighbors or the environment, and the ash left in the stove can be used for fertilizing gardens and plants. The process has been patented in the Middle East and the US.


Cultivars
There are thousands of cultivars of the olive. In Italy alone at least three hundred cultivars have been enumerated, but only a few are grown to a large extent. None of these can be accurately identified with ancient descriptions, though it is not unlikely that some of the narrow-leaved cultivars most esteemed may be descendants of the Licinian olive. The Iberian olives are usually cured and eaten, often after being pitted, stuffed (with pickled pimento, anchovies, or other fillings) and packed in brine in jars or tins.

Since many cultivars are self sterile or nearly so, they are generally planted in pairs with a single primary cultivar and a secondary cultivar selected for its ability to fertilize the primary one. In recent times, efforts have been directed at producing hybrid cultivars with qualities such as resistance to disease, quick growth and larger or more consistent crops.

Some particularly important cultivars of olive include:

* 'Amfissa', excellent quality Greek table olive grown in Amfissa, Central Greece near the oracle of Delphi. Amfissa olives enjoy PDO (Protected designation of origin) status and are equally good for olive oil extraction. The olive grove of Amfissa, which consists of 1,200,000 olive trees is a part of a protected natural landscape.

* 'Bosana', the most common olive grown on Sardinia. It is used mostly for oils.

* 'Manzanilla', a large, rounded-oval fruit, with purple-green skin, originating in Dos Hermanas, Seville, in southern Spain. Rich taste and thick pulp. A prolific bearer, grown around the world.

* 'Frantoio' and 'Leccino'. These cultivars are the principal participants in Italian olive oils from Tuscany. Leccino has a mild sweet flavour while Frantoio is fruity with a stronger aftertaste. Due to their highly valued flavour, these cultivars are now grown in other countries.

* 'Arbequina', a small, brown olive grown in Catalonia, Spain, good for eating and for oil.

* 'Cornicabra', originating in Toledo, Spain, comprises about 12% of Spain's production. It is mainly used for oil.

* 'Empeltre', a medium-sized black olive grown in Spain, good for eating and for oil.

* 'Hojiblanca', originating in the province of Córdoba, Spain, its oil is widely appreciated for its slightly bitter flavour.

* 'Kalamata', a large, black olive with a smooth and meat like taste, named after the city of Kalamata, Greece, used as a table olive. These olives are usually preserved in vinegar or olive oil. Kalamata olives enjoy PDO (Protected designation of origin) status.

* 'Koroneiki', originating from the southern Peloponese, around Kalamata and Mani in Greece. This small olive, though difficult to cultivate, has a high yield of olive oil of exceptional quality.

* 'Picholine' or 'pecholine', originating in the south of France. It is green, medium size, and elongated. The flavour is mild and nutty.

* 'Picual', originating in southern Spain (province of Jaén), it is the most widely cultivated olive in Spain, comprising about 50% of Spain's olive production and around 20% of world olive production. It has a strong but sweet flavour, because of which is widely used in Spain as a olive to eat. Moreover, its oil has some of the best chemical properties found in olive oil, being the richest in oleic acid and E vitamin.

* 'Lucques', originating in the south of France (Aude département). They are green, large, and elongated. The stone has an arcuated shape. Their flavor is mild and nutty.

* 'Souri', originating in Lebanon (the town of Sour (Tyre) and widespread in the Levant. It has a high oil yield and exceptionally aromatic flavor.

* 'Barnea', a modern disease-resistant cultivar that produces a generous crop. It is used both for oil and for table olives. The oil has a strong flavour with a hint of green leaf. Barnea is widely grown in the southern hemisphere, particularly in Australia and New Zealand.

* 'Mission' originated on the California Missions and is now grown throughout the state. They are black and generally used for table consumption.


Growth & Propagation
Olive trees show a marked preference for calcareous soils, flourishing best on limestone slopes and crags, and coastal climate conditions. They tolerate drought well, thanks to their sturdy and extensive root system. Olive trees can be exceptionally long-lived, up to several centuries, and can remain productive for as long, provided they are pruned correctly and regularly.

The olive tree grows very slowly, but over many years the trunk can attain a considerable diameter. A. P. de Candolle recorded one exceeding 10 m in girth. The trees rarely exceed 15 m in height, and are generally confined to much more limited dimensions by frequent pruning. The yellow or light greenish-brown wood is often finely veined with a darker tint; being very hard and close-grained, it is valued by woodworkers.

The olive is propagated in various ways, but cuttings or layers are generally preferred; the tree roots easily in favourable soil and throws up suckers from the stump when cut down. However, yields from trees grown from suckers or seeds are poor; it must be budded or grafted onto other specimens to do well (Lewington and Parker, 114). Branches of various thickness cut into lengths of about 1 m and planted deeply in manured ground, soon vegetate. Shorter pieces are sometimes laid horizontally in shallow trenches and, when covered with a few centimetres of soil, rapidly throw up sucker-like shoots. In Greece, grafting the cultivated tree on the wild form is a common practice. In Italy, embryonic buds, which form small swellings on the stems, are carefully excised and planted beneath the surface, where they grow readily, their buds soon forming a vigorous shoot.

Occasionally the larger boughs are marched, and young trees thus soon obtained. The olive is also sometimes raised from seed, the oily pericarp being first softened by slight rotting, or soaking in hot water or in an alkaline solution, to facilitate germination.

Where the olive is carefully cultivated, as in Languedoc and Provence, the trees are regularly pruned. The pruning preserves the flower-bearing shoots of the preceding year, while keeping the tree low enough to allow the easy gathering of the fruit. The spaces between the trees are regularly fertilized. The crop from old trees is sometimes enormous, but they seldom bear well two years in succession, and in many instances a large harvest can only be reckoned upon every sixth or seventh season.

A calcareous soil, however dry or poor, seems best adapted to its healthy development, though the tree will grow in any light soil, and even on clay if well drained; but, as remarked by Pliny, the plant is more liable to disease on rich soils, and the oil is inferior to the produce of the poorer and more rocky ground.

In general, a temperature below 14 °F (-10 °C) may cause considerable injury to a mature tree, but (with the exception of juvenile trees) a temperature of 16 °F (-9 °C) will normally cause no harm.


Fruit Harvest & Processing
Olives are harvested in the fall. More specifically, green olives are picked at the end of September to about the middle of November. Blond olives are picked from the middle of October to the end of November and Black olives are collected from the middle of November to the end of January or early February. Some Italian and Greek olives are harvested by hand, as the terrain can be mountainous which inhibits harvesting by machine. As a result, the fruit is not bruised which leads to a superior finished product. Furthermore, the fact that branches are sawn off as part of the method of hand harvesting, ensures the health of the tree for future production.

Most olives today are harvested by shaking the boughs or the whole tree. Another method involves standing on a ladder and "milking" the olives into a sack tied around the harvester's waist. Using olives found lying on the ground can result in poor quality oil.

In southern Europe the olive harvest is in winter, continuing for several weeks, but the time varies in each country, and also with the season and the kinds cultivated. A device called the oli-net wraps around the trunk of the tree and opens to form an umbrella-like catcher; workers can then harvest the fruit without the weight of the load around their neck. Another device, the oliviera, is an electric tool that connects to a battery. The oliviera has large tongs that are spun around quickly, removing fruit from the tree. This method is used for olives used for oil. Table olive varieties are more difficult to harvest, as workers must take care not to damage the fruit; baskets that hang around the worker's neck are used.

The amount of oil contained in the fruit differs greatly in the various cultivars; the pericarp is usually 60–70% oil. Typical yields are 1.5-2.2 kg of oil per tree per year.


Traditional Fermentation & Curing
With one exception (Thassos Olives), olives are inedible when picked from the tree. This is due to the glucoside in their flesh, which makes them taste extremely bitter. To remove this glucoside and render the olive edible, the fruit must be cured.

Olives freshly picked from the tree contain phenolic compounds and oleuropein, a glycoside which makes the fruit unpalatable for immediate consumption. There are many ways of processing olives for table use. Traditional methods use the natural microflora on the fruit and procedures which select for those that bring about fermentation of the fruit. This fermentation leads to three important outcomes: the leaching out and breakdown of oleuropein and phenolic compounds; the creation of lactic acid, which is a natural preservative; and a complex of flavoursome fermentation products. The result is a product which will store with or without refrigeration.

One basic fermentation method is to get food grade containers, which may include plastic containers from companies which trade in olives and preserved vine leaves. Many bakeries also recycle food grade plastic containers which are well sized for olive fermentation; they are 10 to 20 litres in capacity. Freshly picked olives are often sold at markets in 10 kg trays. Olives should be selected for their firmness if green and general good condition. Olives can be used green, ripe green (which is a yellower shade of green, or green with hints of colour), through to full purple black ripeness. The olives are soaked in water to wash them, and drained. 7 litres (which is 7 kg) of room temperature water is added to the fermentation container, and 800 g of sea salt, and one cup (300 g) of white vinegar (white wine or cider vinegar). The salt is dissolved to create a 10% solution (the 800 g of salt is in an 8 kg mixture of salt and water and vinegar). Each olive is given a single deep slit with a small knife (if small), or up to three slits per fruit (if large, e.g., 60 fruit per kg). If 10 kg of olives are added to the 10% salt solution, the ultimate salinity after some weeks will be around 5 to 6% once the water in the olives moves into solution and the salt moves into the olives. The olives are weighed down with an inert object such as a plate so they are fully immersed and lightly sealed in their container. The light sealing is to allow the gases of fermentation to escape. It is also possible to make a plastic bag partially filled with water, and lay this over the top as a venting lid which also provides a good seal. The exclusion of oxygen is useful but not as critical as when grapes are fermented to produce wine. The olives can be tasted at any time as the bitter compounds are not poisonous, and oleuropein is a useful antioxidant in the human diet.

The olives are edible within 2 weeks to a month, but can be left to cure for up to three months. Green olives will usually be firmer in texture after curing than black olives.

There are several methods via which olives can be cured: lye-curing, salt-curing, brine-curing and fresh water-curing. Lye-curing, an unnatural method, is the one resulting in the worst taste as it leeches much of the fruits' flavor. Salt-curing (also known as dry-curing) involves packing the olives in plain salt for minimum of a month, which produces a salty and wrinkled olive. Olives are placed in a water and salt solution for a few days or more as a part of the of brine-curing process. Fresh-water curing involves soaking the olives in a succession of baths, of which the water is changed daily.

Olives can be flavoured by soaking them in various marinades, or removing the pit and stuffing them. Herbs, spices, olive oil, feta, capsicum (pimento), chili, lemon zest, lemon juice, garlic cloves, wine, vinegar, juniper berries, and anchovies are popular flavourings. Sometimes the olives are lightly cracked with a hammer or a stone to trigger fermentation. This method of curing adds a slightly bitter taste.


Pests, Diseases, & Weather
A fungus, Cycloconium oleaginum, can infect the trees for several successive seasons, causing great damage to plantations. A species of bacterium, Pseudomonas savastanoi pv. oleae, induces tumour growth in the shoots. Certain lepidopterous caterpillars feed on the leaves and flowers. More serious damage is caused by olive-fly attacks to the fruit.

A pest which spreads through olive trees is the black scale bug, a small black beetle that resembles a small black spot. They attach themselves firmly to olive trees and reduce the quality of the fruit; their main predators are wasps. The curculio beetle eats the edges of leaves, leaving sawtooth damage.

Rabbits eat the bark of olive trees and can do considerable damage, especially to young trees. If the bark is removed around the entire circumference of a tree it is likely to die.

In France and north-central Italy olives suffer occasionally from frost. Gales and long-continued rains during the gathering season also cause damage.


Production
Olives are the most extensively cultivated fruit crop in the world. Cultivation area tripled from 2.6 to 8.5 million hectares between 1960 and 2004. The ten largest producing countries, according to the Food and Agriculture Organization, are all located in the Mediterranean region and produce 95% of the world's olives.