Olive

This article is about the tree. For its edible fruit, see Olive (fruit). For its oil, see Olive oil. For other uses, see Olive (disambiguation).
Olive Tree
Olea europaea, Dead Sea, Jordan
Olea europaea, Dead Sea, Jordan
Scientific classification
Kingdom: Plantae
Division: Magnoliophyta
Class: Magnoliopsida
Order: Lamiales
Family: Oleaceae
Genus: Olea
Species: O. europaea
Binomial name
Olea europaea
L.
19th century illustration

The Olive (Olea europaea) is a species of small tree in the family Oleaceae, native to the coastal areas of the eastern Mediterranean region, from Lebanon, Syria and the maritime parts of Asia Minor and northern Iran 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.

Contents

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 four-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 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 colour (black olive). Canned black olives may contain chemicals that turn them black artificially.

History

See also: Olive oil#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.[1] 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."[2] 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.[3]

The leafy branches of the olive tree, olive leaf as a symbol of abundance, glory and peace, were used to crown the victors of friendly games and bloody war. 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[4]

Old olive trees

Olive tree on Ithaca, Greece, that is claimed to be over 1500 years old.

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.[5] Some Italian olive trees are believed to date back to Roman times, although identifying progenitor trees in ancient sources is difficult.

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.[6] Another, on the island of Brijuni (Brioni), Istria in Croatia, a well-known olive tree 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.[7]

According to a recent scientific survey there are tens of ancient olive trees throughout Israel, 1600-2000 years old.[8] Specifically, two giant olive trees in the town of Arabeh and five trees in Dir Hannah, both in Israel's Galilee region, have been determined to be over 3000 years old. All seven trees continue to produce olives.[9]

The olive tree is frequently mentioned in Religious texts such as the Bible, Qur'an and the Book of Mormon, and is one of the symbols of the Greek goddess Athena.

As far back as 3000BC olives were grown commercially in Crete; they may have been the source of the wealth of the Minoan Civilization.[10]

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 millenary trees can be admired.

Cultivation and uses

For more details on this topic, see olive (fruit).
An example of black olives.

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.

The plant and its products are frequently referred to in the Bible, the Book of Mormon, the Qur'an, and by the earliest recorded poets. 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.

Olive plantation in Andalucia, Spain.

Olives are now cultivated in many regions of the world with Mediterranean climates, such as South Africa, Chile, Australia, Mediterranean Basin, Israel, Palestinian Territories 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)[11]; the climate in Argentina changes the external characteristics of the plant but the fruit keeps its original characteristics [12]. Considerable research supports the health-giving benefits of consuming olives, olive leaf and olive oil (see external links below for research results).

The olive tree provides leaves, fruit and oil. Olive leaves are used in medicinal teas.

Subspecies

There are at least five natural subspecies distributed over a wide range:

Cultivars

Small Olive Tree
Large Olive Tree
Olive Tree Leaves
Olive Tree Trunk
Olive Flowers
A young olive plant, germinated from a seed
Monumental tree in Apulia Region - Southern Italy

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:

Growth and 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 are cut into lengths of about 1 m and, planted deeply in manured ground, soon vegetate; shorter pieces are sometimes laid horizontally in shallow trenches, when, covered with a few centimetres of soil, they 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 and processing

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 electronic 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.[16]

Traditional fermentation

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 color), 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 (300g) 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, eg 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. Olives can be flavored 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 flavorings. 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, and 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[17], 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.[18]

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.

Economy

Olive output in 2005

Production

Olives are the most extensively cultivated fruit crop in the world.[19] Cultivation area has tripled from 2.6 to 8.5 million hectares in the past 44 years.

The ten largest producing countries, according to FAO, are all located in the Mediterranean region and produce 95% of the world's olives.

Main countries of production (Year 2003)
Rank Country/Region Production
(in tons)		 Cultivated area
(in hectares)		 Yield
(q/Ha)
— World 17,317,089 8,597,064 20.1
1 Spain 6,160,100 2,400,000 25.7
2 Italy 3,149,830 1,140,685 27.6
3 Greece 2,300,000 765,000 31.4
4 Turkey 1,800,000 594,000 30.3
5 Syria 998,988 498,981 20.0
6 Tunisia 500,000 1,500,000 3.3
7 Morocco 470,000 550,000 8.5
8 Egypt 318,339 49,888 63.8
9 Algeria 300,000 178,000 16.9
10 Portugal 280,000 430,000 6.5
11 Lebanon 180,000 230,000 4.5

Olive as an invasive species

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.[20]

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.[21]

References

  1. ↑ Homer, "Odyssey, book 5", ca 800BC
  2. ↑ "Me pascunt olivae, me cichorea levesque malvae." Horace, Odes 1.31.15, ca 30 BC
  3. ↑ Letter from Lord Monboddo to John Hope, 29 April, 1779; reprinted by William Knight 1900 ISBN 1-85506-207-0
  4. ↑ Gooch, Ellen, "10+1 Things you may not know about olive oil" Epikouria Magazine, Fall/Spring (2005)
  5. ↑ Lewington, A., & Parker, E. (1999) Ancient Trees., pp 110–113, London: Collins & Brown Ltd. ISBN 1-85585-704-9
  6. ↑ O. Rackham, J. Moody, The Making of the Cretan Landscape, 1996, cited in F. R. Riley (2002). Olive Oil Production on Bronze Age Crete: Nutritional properties, Processing methods, and Storage life of Minoan olive oil. Oxford Journal of Archaeology 21 (1): 63–75
  7. ↑ "Old Olive Tree". Brijuni National Park. Retrieved on 2007-03-10.
  8. ↑ M. Kislew, Y. Tabak & O. Simhoni, Identifying the Names of Fruits in Ancient Rabbinic Literature, 'Leshonenu' (Hebrew), vol. 69, p.279
  9. ↑ M. Kislew, Y. Tabak & O. Simhoni, Identifying the Names of Fruits in Ancient Rabbinic Literature, 'Leshonenu' (Hebrew), vol. 69, p.279
  10. ↑ Gooch, Ellen, "10+1 Things you may not know about olive oil", Epikouria Magazine, (Fall/ Spring 2005).
  11. ↑ Enciclopedia Universal Europeo Americana. Volume 15. Madrid. 1981. Espasa-Calpe S.A. ISBN 84-239-4-500-6 (Complete Encyclopedia) and ISBN 84-239-4-515-4 (Volume 15 )
  12. ↑ 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
  13. ↑ Fotiadi, Elena "Unusual Olives", Epikouria Magazine (Spring/Summer 2006)
  14. ↑ Belaj et al. (September 2002). "Genetic diversity and relationships in olive (Olea europaea L.) germplasm collections as determined by randomly amplified polymorphic DNA". 'TAG Theoretical and Applied Genetics' (Springer Berlin / Heidelberg) Volume 105, Number 4. http://www.springerlink.com/content/dlb533pw9cbwc59e/. Retrieved on 2007-08-31. 
  15. ↑ PFTA & Canaan Fair Trading. "A Brief Study of Olives and Olive Oil in Palestine". Zatoun. Retrieved on 2007-08-31.
  16. ↑ Riley, op.cit.
  17. ↑ 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. 32:166–169.
  18. ↑ Burr, M. 1999. Australian Olives. A guide for growers and producers of virgin oils, 4th edition.
  19. ↑ FAO, 2004
  20. ↑ Lumaret, R. & Ouazzani, N. (2001) Ancient wild olives in Mediterranean forests. Nature 413: 700
  21. ↑ Dirk HR Spennemann & Allen, L.R. (2000) Feral olives (Olea europaea) as future woody weeds in Australia: a review. Australian Journal of Experimental Agriculture 40: 889–901.

See also

External links