| Olive Tree Olea europaea |
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|---|---|
| Olea europaea, Dead Sea, Jordan | |
| Scientific classification | |
| Kingdom: | Plantae |
| (unranked): | Angiosperms |
| (unranked): | Eudicots |
| (unranked): | Asterids |
| Order: | Lamiales |
| Family: | Oleaceae |
| Genus: | Olea |
| Species: | O. europaea |
| Binomial name | |
| Olea europaea L. |
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The olive ( /ˈɑːləv/ or /ˈɒlɨv/), Olea europaea) is a species of a small tree in the family Oleaceae, native to the coastal areas of the eastern Mediterranean Basin (the adjoining coastal areas of southeastern Europe, western Asia and northern Africa) as well as northern Iran at the south end of the Caspian Sea.
Its fruit, also called the olive, is of major agricultural importance in the Mediterranean region as the source of olive oil. The tree and its fruit give its name to the plant family, which also includes species such as lilacs, jasmine, Forsythia and the true ash trees (Fraxinus). The word derives from Latin olīva which in turn comes from the Greek ἐλαία (elaía)[1][2] ultimately from Mycenaean Greek 𐀁𐀨𐀷 e-ra-wa ("elaiva"), attested in Linear B syllabic script.[3][4] The word 'oil' in multiple languages ultimately derives from the name of this tree and its fruit.
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The olive tree, Olea europaea, is an evergreen tree or shrub native to the Mediterranean, Asia and Africa. It is short and squat, and rarely exceeds 8–15 metres (26–49 ft) in height. The silvery green leaves are oblong in shape, measuring 4–10 centimetres (1.6–3.9 in) long and 1–3 centimetres (0.39–1.2 in) wide. The trunk is typically gnarled and twisted.
The small white, feathery 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 axils of the leaves.
The fruit is a small drupe 1–2.5 centimetres (0.39–0.98 in) long, thinner-fleshed and smaller in wild plants than in orchard cultivars. Olives are harvested in the green to purple stage. Canned black olives may contain chemicals (usually ferrous sulfate) that turn them black artificially.
Olea europaea contains a seed commonly referred to as a pit or a rock.
100g of green olives contains:[5]
The place, time and immediate ancestry of the cultivated olive are unknown. It is assumed that Olea europaea may have arisen from O. chrysophylla in northern tropical Africa and that it was introduced into the countries of the Mediterranean Basin via Egypt and then Crete or Israel, Syria and Asia Minor. Fossil Olea pollen has been found in Macedonia, Greece, and other places around Mediterranean, indicating that this genus is an original element of the Mediterranean flora. Fossilized leaves of Olea were found in the palaeosols of the volcanic Greek island of Santorini (Thera) and were dated about 37.000 B.P. Inprints of larvae of olive whitefly Aleurolobus (Aleurodes) olivinus were found on the leaves. The same insect is commonly found today on olive leaves, showing that the plant-animal co-evolutionary relations have not changed since that time.[6]
The olive is one of the plants most often cited in western literature. In Homer's Odyssey, Odysseus crawls beneath two shoots of olive that grow from a single stock,[7] and in the Iliad, (XVII.53ff) is a metaphoric description of a lone olive tree in the mountains, by a spring; the Greeks observed that the olive rarely thrives at a distance from the sea, which in Greece invariably means up mountain slopes. Greek myth attributed to the primordial culture-hero Aristaeus the understanding of olive husbandry, along with cheese-making and bee-keeping.[8] Olive was one of the woods used to fashion the most primitive Greek cult figures, called xoana, referring to their wooden material; they were reverently preserved for centuries.[9] It was purely a matter of local pride that the Athenians claimed that the olive grew first in Athens.[10] In an archaic Athenian foundation myth, Athena won the patronship of Attica from Poseidon with the gift of the olive. Though, according to the 4th-century BC father of botany, Theophrastus, olive trees ordinarily attained an age of about 200 years,[11] he mentions that the very olive tree of Athena still grew on the Acropolis; it was still to be seen there in the 2nd century AD;[12] and when Pausanias was shown it, ca 170 AD, he reported "Legend also says that when the Persians fired Athens the olive was burnt down, but on the very day it was burnt it grew again to the height of two cubits."[13] Indeed, olive suckers sprout readily from the stump, and the great age of some existing olive trees shows that it was perfectly possible that the olive tree of the Acropolis dated to the Bronze Age. The olive was sacred to Athena and appeared on the Athenian coinage.
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."[14] 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.[15]
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. Over the years, the olive has been the symbol of peace, wisdom, glory, fertility, power and purity.
The olive was one of the main elements in ancient Israelite cuisine. Olive oil was used not only for food and for cooking, but also for lighting, sacrificial offerings, ointment, and anointment for priestly or royal office.[16]
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 leaf that a dove brought back to Noah to demonstrate that the flood was over. The olive is listed in the Hebrew Bible (Deut 8:8) as one of the seven species that are noteworthy products of the Land of Israel.[17]
The Mount of Olives east of Jerusalem is mentioned several times. The Allegory of the Olive Tree in St. Paul's Epistle to the Romans (which reappears in greatly expanded form in the Book of Jacob in the Book of Mormon) refers to the scattering and gathering of Israel. It compares the Israelites and gentiles to tame and wild olive trees. The olive tree itself, as well as olive oil and olives, play an important role in the Bible.[18]
The olive tree and olive oil are mentioned seven times in the Quran,[19] and the olive is praised as a precious fruit. Most notably, it is mentioned in one of the most famous verses of the Quran, Ayat an-Nur: "Allah is the Light of the heavens and the earth. The metaphor of His Light is that of a niche in which is a lamp, the lamp inside a glass, the glass like a brilliant star, lit from a blessed tree, an olive, neither of the east nor of the west, its oil all but giving off light even if no fire touches it. Light upon Light. Allah guides to His Light whoever He wills and Allah makes metaphors for mankind and Allah has knowledge of all things." (Quran, 24:35). Olive tree and olive oil health benefits have been propounded in Prophetic medicine. The Prophet Mohamed is reported to have said: "Take oil of olive and massage with it – it is a blessed tree" (Sunan al-Darimi, 69:103).
The olive tree is native to the Mediterranean region and Western Asia, and spread to nearby countries from there. It is estimated the cultivation of olive trees began more than 7000 years ago. 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.[20] The ancient Greeks used to smear olive oil on their bodies and hair as a matter of grooming and good health.
Theophrastus, in On the Nature of Plants, does not give as systematic and detailed an account of olive husbandry as he does of the vine, but he makes clear (in 1.16.10) that the cultivated olive must be vegetatively propagated; indeed, the pits give rise to thorny, wild-type olives, spread far and wide by birds. Theophrastus reports how the bearing olive can be grafted on the wild olive, for which the Greeks had a separate name, kotinos.[21]
After the 16th century, the Europeans brought the olive to the New World, and its cultivation began in Mexico, Peru, Chile and Argentina, and then in the 18th century in California. 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.
The olive tree, Olea europaea, is very hardy: drought-, disease- and fire-resistant, it can live to a great age. Its root system is robust and capable of regenerating the tree even if the above-ground structure is destroyed. The older an olive tree is, the broader and more gnarled its trunk appears. Many olive trees in the groves around the Mediterranean are said to be hundreds of years old, while an age of 2,000 years is claimed for a number of individual trees; in some cases, this has been scientifically verified.
Pliny the Elder told about a sacred Greek olive tree that was 1,600 years old. An olive tree in west Athens, named "Plato's Olive Tree", was said to be a remnant of the grove within which Plato's Academy was situated, which would make it approximately 2,400 years old. The tree comprised a cavernous trunk from which a few branches were still sprouting in 1975, when a traffic accident caused a bus to fall on and uproot it. Since then, the trunk has been preserved and displayed in the nearby Agricultural University of Athens. A supposedly older tree, the "Peisistratos Tree", is located by the banks of the Cephisus River, in the municipality of Agioi Anargyroi, and is said to be a remnant of an olive grove that was planted by Athenian tyrant Peisistratos in the 6th century BC. Numerous ancient olive trees also exist near Pelion in Greece.
An olive tree in Algarve, Portugal, is 2000 years old, according to radiocarbon dating.[22]
The age of an olive tree in Crete, claimed to be over 2,000 years old, has been confirmed on the basis of tree ring analysis.[23]
An olive tree in Bar, Montenegro, is claimed to be over 2,000 years old.[24]
An 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/66 lb per year), which is made into top quality olive oil.[25]
The town of Bshaale, Lebanon claims to have the oldest olive trees in the world (4000 BC for the oldest), but no scientific study supports these claims. Other trees in the towns of Amioun appear to be at least 1,500 years old. [26][27]
According to a recent scientific survey, there are dozens of ancient olive trees throughout Israel and Biblical Palestine, 1,600–2,000 years old.[28] Ancient trees include two giant olive trees in the Arab town of Arraba and five trees in Deir Hanna, both in the Galilee region, which have been determined to be over 3,000 years old,[28] although the credibility of the study that produced these dates has been questioned. All seven trees continue to produce olives.
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.[29]
Some Italian olive trees are believed to date back to Roman times, although identifying progenitor trees in ancient sources is difficult. A tree located in Santu Baltolu di Carana (municipality of Luras) in Sardinia, Italy, named with respect as the Ozzastru by the inhabitants of the region, is claimed to be 3,000 to 4,000 years old according to different studies. There are several other trees of about 1,000 years old within the same garden. The XV sec. trees of Olivo della Linza located in Alliste province of Lecce in Puglia were noted by Bishop Ludovico de Pennis during his pastoral visit to the Roman Catholic Diocese of Nardò-Gallipoli in 1452.[30]
The olive tree, Olea europaea, has been cultivated for olive oil, fine wood, olive leaf, and the olive fruit. 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/34.5 mi) as the limit. Modern experience does not always confirm this, and, though showing a preference for the coast, they have 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, Peru, Australia, 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).[31] The climate in Argentina changes the external characteristics of the plant but the fruit keeps its original features.[32] The northernmost olive grove is placed in Anglesey, an island off the north west coast of Wales, in the United Kingdom.[33]
Considerable research supports the health-giving benefits of consuming olives, olive leaf and olive oil (see external links below for research results). Olive leaves are used in medicinal teas.
Olives are now being looked at[34] 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 same reference claims that 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 (for example).[35]
There are six natural subspecies of Olea europaea distributed over a wide range:[36][37]
The subspecies maroccana and cerasiformis are respectively hexaploid and tetraploid.[38]
There are thousands of cultivars of the Olea europaea olive tree. 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. Some also pickle olives at home.
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 Olea europaea include:
Olive trees, Olea europaea, show a marked preference for calcareous soils, flourishing best on limestone slopes and crags, and coastal climate conditions. They grow in any light soil, even on clay if well drained, but in rich soils they are predisposed to disease and produce poorer oil than in poorer soil. (This was noted by Pliny the Elder.) Olives like hot weather, and temperatures below −10 °C (14 °F) may injure even a mature tree. They tolerate drought well, thanks to their sturdy and extensive root system. Olive trees can live for several centuries, and can remain productive for as long if they are pruned correctly and regularly.
Olives grow very slowly, and over many years the trunk can attain a considerable diameter. A. P. de Candolle recorded one exceeding 10 metres (33 ft) in girth. The trees rarely exceed 15 metres (49 ft) 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. There are only a handlful of olive varieties that can be used to cross-pollinate. Pendolino olive trees are partially self-fertile, but pollenizers are needed for a large fruit crop. Other compatible olive tree pollenizers include Leccino and Maurino. Pendolino olive trees are used extensively as pollenizers in large olive tree groves.
Olives are propagated by various methods. The preferred ways are cuttings and layers; 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; they 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 metre (3.3 ft) 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 tree is a common practice. In Italy, embryonic buds, which form small swellings on the stems, are carefully excised and planted under the soil surface, where they soon form a vigorous shoot.
The olive is also sometimes grown from seed. To facilitate germination, the oily pericarp is first softened by slight rotting, or soaked in hot water or in an alkaline solution.
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 cases a large harvest occurs every sixth or seventh season.
Olives are harvested in the autumn and winter. More specifically in the Northern hemisphere, 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. In southern Europe, harvesting is done for several weeks in winter, but the time varies in each country, and with the season and the cultivar.
Most olives today are harvested by shaking the boughs or the whole tree. Using olives found lying on the ground can result in poor quality oil. Another method involves standing on a ladder and "milking" the olives into a sack tied around the harvester's waist. A third method uses a device called an oli-net that wraps around the tree trunk and opens to form an umbrella-like catcher from which workers collect the fruit. Another method uses an electric tool, the oliviera, that has large tongs that spin 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. In some places in Italy and Greece, olives are harvested by hand because the terrain is too mountainous for machines. As a result, the fruit is not bruised, which leads to a superior finished product. The method also involves sawing off branches, which is healthy for future production.[42]
The amount of oil contained in the fruit differs greatly by cultivar; the pericarp is usually 60–70% oil. Typical yields are 1.5–2.2 kg (3.3–4.9 lb) of oil per tree per year.[23]
Olives are a naturally bitter fruit that is typically subjected to fermentation or cured with lye or brine to make it more palatable.
Green olives and black olives are typically washed thoroughly in water to remove oleuropein, a bitter carbohydrate. Sometimes they are also soaked in a solution of food grade sodium hydroxide 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.
Freshly picked olive fruit is not palatable because it contains phenolic compounds and oleuropein, a glycoside which makes the fruit too bitter, although not unhealthy.[42] (One exception is the throubes olive, which can be eaten fresh.)[43] There are many ways of processing olives for eating. Traditional methods use the natural microflora on the fruit and procedures which select for those flora that ferment 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.
Fresh olives are often sold at markets. Olives can be used green, ripe green (a yellower shade of green, or green with hints of colour), through to full purple black ripeness. Olives should be selected for general good condition and for firmness if green. For fermentation, the olives are soaked in water to wash, then drained. One method uses a ratio of 7 liters (7 kg/15 lb) of room temperature water, plus 800 g (28 oz) of sea salt and 1 cup (300 g/11 oz) of white wine or cider vinegar. Each olive is slit deeply with a small knife; large fruit (e.g., 60 fruit per kg) should be slit in multiple places. The solution is added to a container of olives, and they are weighted down with an inert object, such as a plate, so they are fully immersed and lightly sealed in their container. The gases of fermentation should be able to escape. It is possible to use 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 helpful, but not as critical as when fermenting grapes to produce wine. After some weeks, the salinity drops from 10% to around 5 to 6%, once the water in the olives moves into solution and the salt moves into the olives. The olives are edible within 2 weeks to a month, but can be left to cure for up to three months. They can be tasted at any time because the bitter compounds are not poisonous, and oleuropein is a useful antioxidant in the human diet.
Curing can be done by several methods: lye-curing, salt-curing, brine-curing and fresh water-curing. Salt-curing (also known as dry-curing) involves packing the olives in plain salt for at least a month, which produces a salty and wrinkled olive. Brine-curing involves placing the olives in a salt water solution for a few days or more. Fresh-water curing involves soaking the olives in a succession of baths, of which the water is changed daily.[42] Green olives are usually firmer than black olives.
Olives can also be flavoured by soaking them in various marinades, or removing the pit and stuffing them. Popular flavourings are herbs, spices, olive oil, feta, capsicum (pimento), chili, lemon zest, lemon juice, garlic cloves, wine, vinegar, juniper berries, almonds, and anchovies. Sometimes, the olives are lightly cracked with a hammer or a stone to trigger fermentation. This method of curing adds a slightly bitter taste.
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,[44] 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 scale insect 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.[45]
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.
At the northern edge of their cultivation zone, for instance in Southern France and north-central Italy, olive trees suffer occasionally from frost. Gales and long-continued rains during the gathering season also cause damage.
Olives are one of the most extensively cultivated fruit crops in the world.[46] In 2009 there were 9.9 million hectares planted with olive trees, which is more than twice the amount of land devoted to apples, bananas or mangoes. Only coconut trees and oil palms command more space.[47] Cultivation area tripled from 2,600,000 to 8,500,000 hectares (6,400,000 to 21,000,000 acres) between 1960 and 2004 and in 2008 reached 10.8 mln Ha. 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.
| Rank | Country/Region | Production (in tons) |
Cultivated area (in hectares) |
Yield (q/Ha) |
|---|---|---|---|---|
| — | World | 18,241,809 | 9,922,836 | 18.383 |
| 1 | Spain | 6,204,700 | 2,500,000 | 24.818 |
| 2 | Italy | 3,600,500 | 1,159,000 | 31.065 |
| 3 | Greece | 2,444,230 (2007) | 765,000 | 31.4 |
| 4 | Turkey | 1,290,654 | 727,513 | 17.740 |
| 5 | Syria | 885,942 | 635,691 | 13.936 |
| 6 | Morocco | 770,000 | 550,000 | 14.000 |
| 7 | Tunisia | 750,000 | 2,300,000 | 3.260 |
| 8 | Egypt | 500,000 | 110,000 | 45.454 |
| 9 | Algeria | 475,182 | 288,442 | 16.474 |
| 10 | Portugal | 362,600 | 380,700 | 9.524 |
| 11 | Lebanon | 210,200 | 250,000 | 6.5 |
| 12 | Jordan | 189,000 | 126,000 | |
| 13 | Libya | 180,000 | ||
| 14 | Argentina | 160,000 | 52,000 | 30.769 |
Since its first domestication, Olea europaea has been spreading back to the wild from planted groves. Its original wild populations in southern Europe have been largely swamped by feral plants.[48]
In some other parts of the world where it has been introduced, most notably South Australia, the olive has become a major woody weed that displaces native vegetation. In South Australia, its seeds are spread by the introduced red fox and by many bird species, including the European starling and the native emu, into woodlands, where they germinate and eventually form a dense canopy that prevents regeneration of native trees.[49] As the climate of South Australia is very dry and bushfire prone, the oil rich feral olive tree substantially increases the fire hazard of native sclerophyll woodlands.[50]
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