|Olea europaea, Dead Sea, Jordan|
The olive ( or , Olea europaea, meaning "olive from/of Europe") is a species of small tree in the family Oleaceae, found in much of Africa, the Mediterranean Basin from Portugal to the Levant, the Arabian Peninsula, and southern Asia as far east as China, as well as the Canary Islands, Mauritius and Réunion. The species is cultivated in many places and considered naturalized in France, Corsica, Greece, Crimea, Egypt, Iran, Iraq, Israel, Italy, Jordan, Palestine, Syria, Lebanon, Java, Norfolk Island, California and Bermuda.
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 ŏlīva ("olive fruit", "olive tree"; "olive oil" is ŏlĕum) which is cognate with the Greek ἐλαία (elaía, "olive fruit", "olive tree") and ἔλαιον (élaion, "olive oil"). The oldest attested forms of the latter two words in Greek are respectively the Mycenaean 𐀁𐀨𐀷, e-ra-wa, and 𐀁𐀨𐀺, e-ra-wo or 𐀁𐁉𐀺, e-rai-wo, written in the Linear B syllabic script. The word "oil" in multiple languages ultimately derives from the name of this tree and its fruit.
- Description 1
- Cultivars 2.1
- Prehistory 3.1
- Americas, Japan 3.2
Symbolic connotations 4
- Ancient Egypt 4.1
- Ancient Israel and Hebrew Bible 4.2
- Ancient Greece 4.3
- Ancient Rome 4.4
- New Testament 4.5
- Islam 4.6
- Table Olives 5.1
- Traditional fermentation and curing 5.2
- Olive wood 5.3
Growth and propagation 6.1
- Old olive trees 6.1.1
- Pests, diseases, and weather 6.1.2
- As an invasive species 6.1.3
- Fruit harvest and processing 6.2
- Growth and propagation 6.1
- Production 7
- Nutrition 8
- Gallery 9
- See also 10
- References 11
- External links 12
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 m (26–49 ft) in height. However, the Pisciottana, a unique variety comprising 40,000 trees found only in the area around Pisciotta in the Campania region of southern Italy often exceeds this, with correspondingly large trunk diameters. The silvery green leaves are oblong, measuring 4–10 cm (1.6–3.9 in) long and 1–3 cm (0.39–1.18 in) wide. The trunk is typically gnarled and twisted.
The fruit is a small drupe 1–2.5 cm (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 artificially turn them black. Olea europaea contains a seed commonly referred to in American English as a pit or a rock, and in British English as a stone.
There are six natural subspecies of Olea europaea distributed over a wide range:
- Olea europaea subsp. europaea (Mediterranean Basin)
- Olea europaea subsp. cuspidata (from South Africa throughout East Africa, Arabia to South West China)
- Olea europaea subsp. guanchica (Canaries)
- Olea europaea subsp. cerasiformis (Madeira)
- Olea europaea subsp. maroccana Morocco
- Olea europaea subsp. laperrinei (Algeria, Sudan, Niger)
Wild growing forms of the olive are sometimes treated as the species Olea oleaster.
There are hundreds of cultivars of the olive tree (Olea europaea). An olive's cultivar has a significant impact on its color, size, shape, and growth characteristics, as well as the qualities of olive oil. Olive cultivars may be used primarily for oil, eating, or both. Olives for consumption are generally referred to as "table olives".
Since many olive 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.
The edible olive has been cultivated for at least 5,000 to 6,000 years, with the most ancient evidence of olive cultivation having been found in Syria, Palestine, and Crete. The olive tree is native to the Mediterranean region and Western Asia, and spread to nearby countries from there.
The immediate ancestry of the cultivated olive is 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 the Levant, Syria, Tunisia and Asia Minor. Fossil Olea pollen has been found in Macedonia, Greece, and other places around the 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 BP. Imprints 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.
Olives are not native to the Americas. The Spanish colonists brought the olive to the New World where its cultivation prospered in present-day Peru and Chile. The first precious seedlings from Spain were planted in Lima by Antonio de Rivera in 1560. Olive tree cultivation quickly spread along the valleys of South America's dry Pacific coast where the climate was similar to the Mediterranean. The Spanish missionaries established the tree in the 18th century in California. It was first cultivated at Mission San Diego de Alcalá in 1769 or later around 1795. Orchards were started at other missions but in 1838 an inspection found only two olive orchards in California. Oil tree cultivation gradually became a highly successful commercial venture from the 1860s onward. In Japan the first successful planting of olive trees happened in 1908 on Shodo Island which became the cradle of olive cultivation. It is estimated that there are about 865 million olive trees in the world today (as of 2005), and the vast majority of these are found in Mediterranean countries, although traditionally marginal areas account for no more than 25% of olive planted area and 10% of oil production.
Olive oil has long been considered sacred. The olive branch was often a symbol of abundance, glory and peace. The leafy branches of the olive tree were ritually offered to deities and powerful figures as emblems of benediction and purification, and they were used to crown the victors of friendly games and bloody wars. Today, olive oil is still used in many religious ceremonies. Over the years, the olive has been the symbol of peace, wisdom, glory, fertility, power and purity.
Leafy branches of the olive tree were found in Tutankhamun's tomb.
Ancient Israel and Hebrew Bible
The olive was one of the main elements in ancient Israelite cuisine. Olive oil was used for not only food and cooking, but also lighting, sacrificial offerings, ointment, and anointment for priestly or royal office.
The olive tree is one of the first plants mentioned in the Hebrew Bible and in the Christian Old Testament, and one of the most significant. It was an olive leaf that a dove brought back to Noah to demonstrate that the flood was over (Book of Genesis, 8:11). The olive is listed in Deuteronomy, 8:8 as one of the seven species that are noteworthy products of the Land of Israel.
The ancient Greeks used to smear olive oil on their bodies and hair as a matter of grooming and good health.
Olive oil 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.
In Homer's Odyssey, Odysseus crawls beneath two shoots of olive that grow from a single stock, 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. 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. It was purely a matter of local pride that the Athenians claimed that the olive grew first in Athens. 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, 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; and when Pausanias was shown it, c. 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." 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.
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.
According to Pliny the Elder a vine, a fig and an olive tree grew in the middle of the Roman Forum, the latter was planted to provide shade (the garden plot was recreated in the 20th century). 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.
Vitruvius describes of the use of charred olive wood in tying together walls and foundations in his De Architectura:
The thickness of the wall should, in my opinion, be such that armed men meeting on top of it may pass one another without interference. In the thickness there should be set a very close succession of ties made of charred olive wood, binding the two faces of the wall together like pins, to give it lasting endurance. For that is a material which neither decay, nor the weather, nor time can harm, but even though buried in the earth or set in the water it keeps sound and useful forever. And so not only city walls but substructures in general and all walls that require a thickness like that of a city wall, will be long in falling to decay if tied in this manner.
The Mount of Olives east of Jerusalem is mentioned several times in the New Testament. 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 to a tame olive tree and the Gentiles to a wild olive branch. The olive tree itself, as well as olive oil and olives, play an important role in the Bible.
The olive tree and olive oil are mentioned seven times in the Quran, 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 One who guides those in the heavens and on the earth. (This lamp is) lit from a blessed tree, an olive neither of the east nor of the west, its oil almost giving off light even though no fire touches it. Light upon Light. Allah guides 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. Muhammad 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, Olea europaea, has been cultivated for olive oil, fine wood, olive leaf, and the olive fruit. 90% of all harvested olives are turned in to oil, while about 10% are used as table olives.
Table olives are classified by the IOC into 3 groups according to the degree of ripeness achieved before harvesting:
1. Green Olives. Picked when they have obtained full size, but before the ripening cycle has begun. Usually shades of green to yellow.
2. Semi-ripe or Turning Colour Olives. Picked at the beginning of the ripening cycle, when the colour has begun to change from green to multi-colour shades of red to brown. Only the skin is coloured as the flesh of the fruit lacks pigmentation at this stage, unlike that of ripe olives.
3. Black Olives or Ripe Olives. Picked at full maturity when fully ripe. Found in assorted shades of purple to brown to black.
Traditional fermentation and curing
Raw or fresh olives are naturally very bitter; to make them palatable, olives must be cured and
- Olea europaeaBlue planet biomes: Olive trees — — cultivation history + horticulture.
- Olea europaeaAgricultural Research Service (ARS); Germplasm Resources Information Network (GRIN): — species treatment, native range, + links.
- (European olive)europaea ssp. Olea europaeaUSDA Plants Profile for
- (African olive)cuspidata ssp. Olea europaeaUSDA Plants Profile for
- ) — U.C. Photo galleryOlea europaeaOlive trees (
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- In particular from a dialect that preserved digamma into historical times; thus *ἐλαίϝα (OLD s.v. oliva, Ernout & Meillet s.v. oleum).
- e-ra-wa "Mycenaean (Linear b) – English Glossary". www.explorecrete.com.
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- History of Shodoshima Town
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- Cooper, John (1993). Eat and Be Satisfied: A Social History of Jewish Food. New Jersey: Jason Aronson Inc. pp. 4–9. . See also both the Hebrew and English text in: Deut 8:8
- Homer, Odyssey, book 5".
- "He learned from the Nymphai how to curdle milk, to make bee-hives, and to cultivate olive-trees, and was the first to instruct men in these matters." (Diodorus Siculus, 4. 81. 1).
- Toward the end of the 2nd century AD, the traveler Pausanias saw many such archaic cult figures.
- "Indeed it is said that at that [ancient] time there were no olives anywhere save at Athens." (Herodotus, 5. 82. 1 ).
- Theophrastus, On the Causes of Plants,, 4.13.5., noted by Signe Isager and Jens Erik Skydsgaard, Ancient Greek Agriculture, An introduction, 1992, p. 38.
- "...which is still shown in the Pandroseion" (pseudo-Apollodorus, Bibliotheke, 3.14.1).
- Pausanias, Description of Greece 1. 27. 1.
- Isager and Skydsgaard 1992, p. 35.
- Encyclopaedia Romana
- "Me pascunt olivae, me cichorea levesque malvae." Horace, Odes 1.31.15, c. 30 BC
- Letter from Lord Monboddo to John Hope, 29 April 1779; reprinted by William Knight 1900 ISBN 1-85506-207-0
- Vitruvius Pollio, The Ten Books on Architecture Harvard University Press, (1914) Book1, Ch.V, Sec.3, p.22
- Balfour, John Hutton (1885) "Plants of the Bible".
- Viktoria Hassouna (2010). Virgin Olive Oil. p. 23.
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- Silva, T., et al. "Characterization of yeasts from Portuguese brined olives, with a focus on their potentially probiotic behavior." LWT-Food Science and Technology 44.6 (2011): 1349-1354.
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- Botta, Cristian, and Luca Cocolin. "Microbial dynamics and biodiversity in table olive fermentation: culture-dependent and-independent approaches." Frontiers in microbiology 3 (2012).
- University of Catania PhD in Food Science and Technology, Food Microbiology: "Isolation and characterization of yeasts isolated from naturally fermented olives with brine bioprotective function" Laboratory of Food Microbiology, DISPA, Agrarian Faculty.
- Enciclopedia Universal Europeo Americana. Volume 15. Madrid. 1981. Espasa-Calpe S.A. ISBN 84-239-4500-6 (Complete Encyclopedia) and ISBN 84-239-4515-4 (Volume 15 )
- Discriminación de variedades de olivo a través del uso de caracteres morfológigos y de marcadores moleculares. 2001. Cavagnaro P., J. Juárez, M Bauza & R.W. Masuelli. AGRISCIENTA. Volume 18:27–35
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- Koutoudis, Dennis. "The Pelion Estates". Retrieved 2012-11-10.
- Oliver Rackham; Jennifer Alice Moody (1996). The making of the Cretan landscape. Manchester University Press.
- Municipality Bar, "Kod Starog Bara u Tombi (Mirovica) nalazi se maslina stara više od 2,000 godina"- Near the Old Bar in Tombi, there is an olive tree which is 2,000 years old. Bar.me. Retrieved on 2011-12-07.
- "Stara maslina (Old Olive Tree)".
- Al-BAB. "Ancient Olive Tree".
- Drinkwater, Carol (2006). The Olive Route. Weidenfeld & Nicholson.
- M. Kislew, Y. Tabak & O. Simhoni, Identifying the Names of Fruits in Ancient Rabbinic Literature, Leshonenu (Hebrew), vol. 69, p. 279
- Dr Shlomo Lee Abrahmov interviews with Prof. Mordechai Kislev (Kislew) 2010, Prof. Shimon Lavi 2012 and Dr. Jennifer Alice Moody, Crete 2012
- Lewington, A., & Parker, E. (1999) Ancient Trees., pp 110–113, London: Collins & Brown Ltd. ISBN 1-85585-704-9
- Diocese of Nardò–Gallipoli. GCatholic.org
- Janse, J. D. (1982). "Pseudomonas syringae subsp. savastanoi (ex Smith) subsp. nov., nom. rev., the bacterium causing excrescences on Oleaceae and Nerium oleander L". Int. J. Syst. Bacteriol. 32 (2): 166–169.
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- Olives as Weeds Animal and Plant Control Commission of South Australia
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- Battle of the Olive Grove of Koundouros
- Candida tropicalis
- Moria (tree)
- Olive oil
- Polyphenol antioxidant
Centuries old olive tree, Portugal
Olive tree leaves
Olive tree, Israel
Olive tree trunk
Olivo della Linza. 15th century
A young olive plant, germinated from a seed
Cailletier cultivar, with an olive harvest net on the ground, Contes, France
Olive tree, Sithonia, Greece,
Olive fruits, Sardinia
Olive tree, Nepal
Olive trees in the famous Turkish oil region of Edremit District
tyrosols (most abundant)
- oleuropein 72 mg/100g (black) and 56 mg/100g (green)
- free hydroxytyrosol （3,4-DHPEA）82 mg/100g (black) and 59 mg/100g (green)
- demethyloleuropein 23 mg/100g (black) and 13 mg/100g (green)
- oleoside (young fruit)
- 3,4-DHPEA-EDA in fruit but more in olive oils.
- Coumaric acids, all 3 types o, m, and p.
- anthocyanins -fruit only
- flavonols—fruit only
- methyl acetal of the aglycone of ligstroside
- ß-hydroxytyrosol ester of methyl malate
- sinapic acid
- syringic acid
- protocatechuic acid
- 4-hydroxybenzoic acid
- p-hydroxyphenylpropanoic acid
- 4-hydroxyphenylacetic acid
- 3-methoxy-4-hydroxyphenylacetic acid
- ferulic acid
- caffeic acid
Among the phenolics are:
The addition of iron salts such as Iron(II) gluconate, as commonly in canned olives, drastly reduces phenolic content, especially hydroxytyrosol. Total polyphenol contents, as measured by the Folin method, are 117 mg/100 g in black olives and 161 mg/100 g in green olives, as compared to 55 and 21 mg/100 g for extra virgin and virgin olive oil respectively. Olive fruit contain several types of polyphenols, mainly tyrosols, phenolic acids, flavonols and flavones, and for black olives, anthocyanins. During the crushing, kneading and extraction of olive fruit to obtain olive oil, the glycosidic oleuropein, demethyloleuropein and ligstroside are hydrolyzed by endogenous Beta-glucosidases, to form aldehydic aglycones. The aglycones become soluble in the oil phase, whereas the glycosides remain in the water phase, fresh cloudy olive oil contains has the added benefit of these water phase phenolics. Lignans are also found in olive fruit and oils.
Olive tree parts, and olive oil, have a number of common phenolic compounds that might possess positive health effect to the human body, as well as a good source of Vitamin E. The processing of olives (fruit) especially affects their phenolic content, but other parts of the plant also contain phenolics, such as leaves and bark.
|Nutritional value per 100 g (3.5 oz)|
|Energy||609 kJ (146 kcal)|
|Dietary fiber||3.3 g|
|Vitamin A equiv.||
Link to USDA Database entry
Percentages are roughly approximated using US recommendations for adults.
Source: USDA Nutrient Database
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.
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, Croatia, 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.
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, due to damage. Another method involves standing on a ladder and "milking" the olives into a sack tied around the harvester's waist. This method produces high quality oil. 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. Olives harvested by this method are used for oil.
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.
Fruit harvest and processing
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. 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.
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.
As an invasive species
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.
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. Moles and mice also do damage by eating the roots of olives.
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.
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.
There are various Bacillus thuringiensis and spraying with kaolin. Such methods are obligatory for organic olives.
Pests, diseases, and weather
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 15th-century 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.
There are dozens of ancient olive trees throughout Israel and Palestine whose age has earlier been estimated to be 1,600–2,000 years old; however, these estimates could not be supported by current scientific practices. Ancient trees include two giant olive trees in Arraba and five trees in Deir Hanna, both in the Galilee region, which have been determined to be over 3,000 years old, although there is no available data to support the credibility of the study that produced these age estimates and as such the 3000 years age estimate can not be considered valid. 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 purported time of Jesus.
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.
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 or 66 lb per year), which is made into top quality olive oil.
An olive tree in Bar, Montenegro, is claimed to be over 2,000 years old.
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. The age of an olive tree in Crete, the Finix Olive is claimed to be over 2,000 years old; this estimate is based on archaeological evidence around the tree.
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 the olive tree, the broader and more gnarled the trunk becomes. 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.
Old olive trees
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 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 m (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.
Olives grow very slowly, and over many years the trunk can attain a considerable diameter. A. P. de Candolle recorded one exceeding 10 m (33 ft) in girth. The trees rarely exceed 15 m (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.
In situations where extreme cold has damaged or killed the olive tree the rootstock can survive and produce new shoots which in turn become new trees. In this way olive trees can regenerate themselves. In Tuscany in 1985 a very severe frost destroyed many productive, and aged, olive trees and ruined many farmers' livelihoods. However new shoots appeared in the spring and, once the dead wood was removed, became the basis for new fruit-producing trees. In this way an olive tree can 'live' for centuries or even millennia.
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 sunny positions without any shade while 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.
Growth and propagation
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). The climate in Argentina changes the external characteristics of the plant but the fruit keeps its original features. The northernmost olive grove is placed in Anglesey, an island off the north west coast of Wales, in the United Kingdom: but it is too early to say if the growing will be successful, having been planted in 2006.
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 that olive trees would not grow well if planted more than a certain distance from the sea; Theophrastus gives 300 stadia (55.6 km or 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.
Olive wood is very hard and is prized for its durability, colour, high combustion temperature and interesting grain patterns. Because of the commercial importance of the fruit, and the relatively small size of the tree, olive wood and its products are relatively expensive. Common uses of the wood include: kitchen utensils, carved wooden bowls, cutting boards, fine furniture, and decorative items.
California or "artificial ripening" type. (Olives without fermentation). Applied to green and semi-ripe olives. Olives are placed in lye and soaked. Upon their removal they are washed in water injected with compressed air. This process is repeated several times until both oxygen and lye have soaked through to the pit. The repeated, saturated exposure to air oxidises the skin and flesh of the fruit, turning it black in an artificial process that mimics natural ripening. Once fully oxidised or "blackened", they are brined and acid corrected ready for eating.
Salt-cured type. (Olives with minor fermentation). Applied only to ripe olives and usually produced in Morocco or Turkey and other eastern Mediterranean countries. Once picked, the olives are vigorously washed and packed in alternating layers with salt. The high concentrations of salt draw the moisture out of olives, dehydrating and shrivelling them until they look somewhat analogous to a raisin. Once packed in salt fermentation is minimal and only initiated by the most halophilic yeast species such as Debaryomyces hansenii. Once cured, they are sold in their natural state without any additives.
Water-cured type. (Olives with fermentation). Can be applied to green, semi-ripe or ripe preparations. Olives are soaked in water or weak brine and this solution is changed on a daily basis for 10–14 days. The oleuropein in naturally dissolved and leached into the water and removed during a continual soak-wash cycle. Fermentation takes place during the water treatment stage and involves a mixed yeast/bacteria ecosystem. Sometimes, the olives are lightly cracked with a hammer or a stone to trigger fermentation and speed up the fermentation process. Once debittered the olives are brined to concentrations of 8-12% NaCl, acid corrected and ready to eat.
Picholine or directly-brined type. (Olives with fermentation). Can be applied to green, semi-ripe or ripe preparations. Olives are soaked in lye typically for longer periods than Spanish style (e.g. 10–72 hours) until the solution has penetrated three-quarters of the way into the fruit. They are then washed and immediately brined and acid corrected with citric acid to achieve microbial stability. Fermentation still occurs carried out by acidogenic yeast and bacteria, but is more subdued than other methods. The brine is changed on a regular basis to help remove the phenolic compounds and a series of progressively stronger concentrations of NaCl are added until the product is fully stabilized and ready to be eaten.
Sicilian or Greek type. (Olives with fermentation). Applied to green, semi-ripe and ripe olives. Almost identical the Spanish type fermentation process, however the lye treatment process is skipped and the olives are placed directly in fermentation vessels full of brine (8-12% NaCl). The brine is changed on a regular basis to help remove the phenolic compounds. As the caustic treatment is avoided, Lactic acid bacteria are only present in similar numbers to yeast and appear to be outcompeted by the abundant yeasts found on untreated olives. As there is very little acid produced by the yeast fermentation, lactic, acetic, or citric acid is often added to the fermentation stage to stabilize the process.
Spanish or Sevillian type (Olives with fermentation). Most commonly applied to green olive preparation. Around 60% of all the worlds table olives are produced with this method. Olives are soaked in lye (Dilute NaOH, 2-4%) for 8–10 hours to hydrolyse the oleuropein. They are usually considered "treated" when the lye has penetrated two-thirds of the way into the fruit. They are then washed once or several times in water to remove the caustic solution and transferred to fermenting vessels full of brine at typical concentrations of 8-12% NaCl. The brine is changed on a regular basis to help remove the phenolic compounds. Fermentation is carried out by the natural microbiota present on the olives that survive the lye treatment process. Many organisms are involved, usually reflecting the local conditions or "Terroir" of the olives. During a typical fermentation gram-negative enterobacteria flourish in small numbers at first, but are rapidly outgrown by Lactic acid bacteria species such as Leuconostoc mesenteroides, Lactobacillus plantarum, Lactobacillus brevis and Pediococcus damnosus. These bacteria produce lactic acid to help lower the acidity of the brine and therefore stabilize the product against unwanted pathogenic species. A diversity of yeasts then accumulate in sufficient numbers to help complete the fermentation alongside the lactic acid bacteria. Yeast commonly mentioned include the teleomorphs Pichia anomala, Pichia membranifaciens, Debaryomyces hansenii and Kluyveromyces marxianus. Once fermented, the olives are placed in fresh brine and acid corrected ready for market.
There are many types of preparations for table olives depending on local tastes and traditions. The most important commercial examples are:
The curing process may take from a few days, with lye, to a few months with brine or salt packing. With the exception of California style and salt cured olives, all methods of curing involve a major fermentation involving bacteria and yeast that is of equal importance to the final table olive product. Traditional cures, using the natural microflora on the fruit to induce fermentation, lead to two important outcomes: the leaching out and breakdown of oleuropein and other unpalatable phenolic compounds, and the generation of favourable metabolites from bacteria and yeast, such as organic acids, probiotics, glycerol and esters, which affect the sensorial properties of the final table olives. The probiotic qualities of mixed bacterial/yeast olive fermentations are only recently being explored. Of all the metabolites lactic acid is the most important as it acts as a natural preservative lowering the pH of the solution to make the final product more stable against the growth of unwanted pathogenic species. The result is table olives which will store with or without refrigeration, and thus lactic acid bacteria (LAB) dominated fermentations are generally considered the most suitable method of curing olives. Yeast dominated fermentations produce a different suite of metabolites which have less self-preservation characteristics and therefore acid corrected, often with citric acid, in the final processing stage to achieve microbial stability.