Olive
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? Olive |
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 Olea
europaea (Olive),
Lisboa, Portugal
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| Olea
europaea L. |
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The Olive (Olea europaea) is a species of small tree in the family Oleaceae, native to coastal areas of the eastern Mediterranean region, from Syria and the maritime parts of Asia Minor and northern Iran at the south end of the Caspian Sea. Its use as a major agricultural product in preclassical Greece led to its wider distribution throughout the western Mediterranean. Olive trees show a marked preference for calcareous soils, flourishing best on limestone slopes and crags, and coastal climate conditions.
The Wild Olive is a small, straggly tree or shrub to 8-15 m tall with thorny branches. The leaves are opposite, oblong pointed, 4-10 cm long and 1-3 cm broad, dark greyish-green above and pale with whitish scales below. 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 cm long, thinner-fleshed and smaller in wild plants than in orchard cultivars.
Cultivation and uses
The Olive has been used since ancient times for the making of olive oil and for eating of the fruit, which, being bitter in its natural state, are typically subjected to fermentation or cured with lye or brine to be made more palatable.
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 and by the earliest poets. The ancient agriculturists believed that the Olive would not succeed 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 less severe.
Olives are now culivated in many regions of the world such as Australia, New Zealand, and California. Considerable research has been done to support the health benefits of eating olives and olive oil (see external links below for research results).
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. The main Italian cultivars are 'Leccino', 'Frantoio' and 'Carolea'. None of these can be safely identified with ancient descriptions, though it is not unlikely that some of the narrow-leaved cultivars that are most esteemed may be descendants of the Licinian olive. The broad-leaved olive trees of Portugal and Spain bear a larger fruit, but the edible portion (the drupe) has a more bitter flavour and the oil is of poorer quality. These Iberian olives are usually cured and eaten, often after being pitted, stuffed (with pickled pimento, onion, or other garnishes) and jarred in fresh brine.
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, for example, 'Frantoio' and 'Leccino'. 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:
- '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 have been migrated and are now grown in other countries.
- ' Arbequina' is a small, brown olive grown in Catalonia, Spain. As well as being used as a table olive, its oil is highly valued.
- 'Empeltre' is a medium sized, black olive grown in Spain. They are used both as a table olive and to produce a high quality olive oil.
- 'Kalamata' is a big size, black olive, named after the city of Kalamata, Greece, used as a table olive.
- 'Koroneiki' originates from the southern Peloponese, around Kalamata and Mani in Greece. This small olive, though difficult to cultivate, has a high oil yield and produces oil of exceptional quality.
- 'Picholine' originated in the south of France. It is green, medium size, and elongated. Their flavour is mild and nutty.
- 'Lucques' originated in the south of France. They are green, of a large size, and elongated. The bone has an arcuated shape. Their flavour is mild and nutty.
- 'Souri' originated in Lebanon and is widespread in Israel and neighboring countries. It has a high oil yield and exceptionally aromatic flavour.
- 'Barnea' is a modern cultivar bred in Israel to be disease resistant and to produce 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 Israel and in the southern hemisphere, particularly in Australia and New Zealand.
- 'Maalot' is another modern, disease-resistant, Israeli cultivar derived from the North African 'Chemlali' cultivar. The olive is medium sized, round, has a fruity flavour and can be used for oil or for table olives.
Growth and propagation
The olive tree grows very slowly, but over many years the trunk can attain a considerable diameter. Augustin Pyrame de Candolle recorded one exceeding 10 m in girth. Some Italian olive trees have been credited with an antiquity reaching back to the Roman empire such as the Linza olive plants cited before bishop Ludovico de Pennis' pastorale visit to Alliste on 11 May 1452; but the age of such ancient trees is always doubtful during growth, and their identity with old descriptions still more difficult to establish. Trees rarely exceed 15 m in height, and are generally confined to much more limited dimensions by frequent pruning. The wood, of a yellow or light greenish-brown hue, is often finely veined with a darker tint, and, being very hard and close-grained, is valued by the cabinetmaker and ornament turner.
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. 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.
Fruit harvest and processing
Most olives today are harvested by shaking the boughs or the whole tree. Lax practices such as using olives lying on the ground can result in poor quality oil. In southern Europe the olive harvest is in the winter months, continuing for several weeks, but the time varies in each country, and also with the season and the kinds cultivated.
The amount of oil contained in the fruit differs much in the various sorts; the pericarp usually yields from 60 to 70%.
Pests and diseases
A fungus Cycloconium oleaginum can infect the trees for several successive seasons, causing great damage to plantations. A species of bacterium, Pseudomonas savastanoi pv. savastanoi induces tumour growth in the shoots, and certain lepidopterous caterpillars feed on the leaves and flowers, while the main damage is made by the olive-fly attacks to the fruit. In France and north-central Italy olives suffer occasionally from frost. Gales and long-continued rains during the gathering season also cause damage.