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|DESCRIPTION: It is a small, evergreen tree, averaging 12 m or more in height but kept to 6m with regular pruning. The root system is relatively shallow, and will not tolerate waterlogged soils. It has many thin branches with opposite branchlets and shortly-stalked, opposite, lanceolate leaves about 6 cm long, acute, entire and smooth, pale green above and silvery below. The bark is pale grey and the flowers numerous, small and creamy white in colour and are largely hidden by the evergreen leaves and grow on a long stem arising from the leaf axils. The olive produces two kinds of flowers: a perfect flower containing both male and female parts, and a staminate flower with stamens only. The flowers are largely wind pollinated with most olive varieties being self-pollinating, although fruit set is usually improved by cross-pollination with other varieties. There are self-incompatible varieties that do not set fruit without other varieties nearby, and there are varieties that are incompatible with certain others. Incompatibility can also occur for environmental reasons such as high temperatures. The dark purple fruit is a drupe about 2 cm long, ovoid and often pointed, the fleshy part filled with oil. The pulp is bitter, due to tannin in the raw fruit, and contains up to 20% oil. The thick, bony stone has a blunt keel down one side. It contains a single seed. The seeds of a few varieties are green when ripe and some turn a shade of copper brown. The cultivars vary considerably in size, shape, oil-content and flavor. The shapes range from almost round to oval or elongated with pointed ends. The trees reach bearing age in about 4 years.
USES: Olive oil, an unsaturated fat, has recently become more valued for its health benefits; the oil component includes unsaturated fatty acid (70% to 80% oleic acid and 7% to 12% linoleic acid), and small amounts of polyphenols, tocopherols, sterols, and many aromatic compounds. The ripe fruits are pressed to extract the oil, the methods varying in different countries. Virgin oil, greenish in tint, is obtained by pressing crushed fruit in coarse bags and skimming the oil from the tubs of water through which it is conducted. The cake left in the bags is broken up, moistened, and repressed. For use as a dessert fruit the unripe olives are steeped in water to reduce their bitterness. Olive soap is made from olive oil and sodium hydroxide. The beautifully veined wood not only takes a fine polish, but is faintly fragrant, and is much valued for small cabinetwork. It was in olden days carved into statues of gods. The leaves are astringent and antiseptic. Both leaves and bark have valuable febrifugal qualities. The oil is a nourishing demulcent and laxative. Externally, it relieves pruritis, the effects of stings or burns, and is a good vehicle for liniments. With alcohol it is a good hair-tonic. As a lubricant it is valuable in skin, muscular, joint, kidney and chest complaints, or abdominal chill, typhoid and scarlet fevers, plague and dropsies. It is often used in enemas. It is the best fat for cooking, and a valuable article of diet for both sick and healthy of all ages. It can easily be taken with milk, orange or lemon juice, etc.
The high position held by the Olive tree in ancient as in modern days may be realized when it is remembered that Moses exempted from military service men who would work at its cultivation, and that in Scriptural and classical writings the oil is mentioned as a symbol of goodness and purity, and the tree as representing peace and happiness. The oil, in addition to its wide use in diet, was burnt in the sacred lamps of temples, while the victor in the Olympic games was crowned with its leaves.
KILLING T.: It is injured when temperatures fall below -10 degrees C.
GROWING PERIOD: Perennial: olives are long-lived with a life expectancy of 500 years. The trees are also tenacious, easily sprouting back even when chopped to the ground.
FURTHER INF.: The olive is native to the Mediterranean region, tropical and central Asia and various parts of Africa. The olive has a history almost as long as that of Western civilization, its development being one of civilized man's first accomplishments. At a site in Spain, carbon dating has shown olive seed found there to be eight thousand years old. O. europaea may have been cultivated independently in two places, Crete and Syria. Archaeological evidence suggests that olives were being grown in Crete as long ago as 2,500 B.C. From Crete and Syria olives spread to Greece, Rome and other parts of the Mediterranean area. Olives are also grown commercially in California, Australia and South Africa.
Proper pruning is important for the olive. Pruning both regulates production and shapes the tree for easier harvest. The trees can withstand radical pruning, so it is relatively easy to keep them at a desired height. The problem of alternate bearing can also be avoided with careful pruning every year. It should be kept in mind that the olive never bears fruit in the same place twice, and usually bears on the previous year's growth. For a single trunk, prune suckers and any branches growing below the point where branching is desired. Prune flowering branches in early summer to prevent olives from forming. Olive trees can also be pruned to espaliers. None of the cultivated varieties can be propagated by seed. Seed propagated trees revert to the original small-fruited wild variety. The seedlings can, of course, be grafted or chip budded with material from desired cultivars. The variety of an olive tree can also be changed by bark grafting or top working. Another method of propagation is transplanting suckers that grow at the base of mature trees. However, these would have to be grafted if the suckers grew from the seedling rootstock. A commonly practiced method is propagation from cuttings. Thirty-thirty five cm long, two-seven cm wide cuttings from the two-year old wood of a mature tree is treated with a rooting hormone, planted in a light-rooting medium and kept moist. Trees grown from such cuttings can be further grafted with wood from another cultivar. Cutting grown trees bear fruit in about four years.
The type of harvest depends upon fruit use. Oil olives are harvested by hand or by mechanically shaking the tree. Those for pickling must still be harvested by hand as the fruit bruises easily. Olives will grow well on almost any well-drained soil up to pH 8.5 and are tolerant of mild saline conditions. Because the olive has fewer natural enemies than other crops, and because the oil in olives retains the odor of chemical treatments, the olive is one of the least sprayed crops. It requires a long, hot growing season to properly ripen the fruit, no late spring frosts to kill the blossoms and sufficient winter chill to insure fruit set. Hot, dry winds may be harmful during the period when the flowers are open and the young fruits are setting. The trees survive and fruit well even with considerable neglect. The olive tree has a wide range of adaptability. It requires a mild climate with warm summers and cold winters. The tree requires substantial chilling for good fruiting. Olive is considered a drought-resistant species because it thrives in areas where water stress is frequent. Olives are wind pollinated, thus flowering during rain; high temperatures and dry wind conditions are deleterious to good fruit set. Mature olive trees produce huge numbers of flowers, but the fruit set is normally below 5%. Most olive cultivars will set some fruit in a mono-cultivar culture. However, they benefit greatly from cross-pollination. Olives are picked late in autumn or winter, as the oil content and fruit characteristics change with ripening.