OLIVE (WILD OLIVE)
The olive is a fruit similar to the peach or plum, bengali name Jalpai. Within the stone are one or two seeds. Olives tend to have maximum oil content (about 20–30 percent of fresh weight) and greatest weight six to eight months after the blossoms appear. At that stage they are black and will continue to cling to the tree for several weeks. Fruits for oil extraction are allowed to mature, but, for processing as food, immature fruits are picked or shaken off the tree. Hundreds of named varieties of both types of olives, table and oil, are grown in warm climates. In California, olives such as the Mission variety are grown almost exclusively for table use. In Europe, olives such as the Picual, Nevadillo, and Morcal are grown mostly for oil.
The olive is a fruit similar to the peach or plum, bengali name Jalpai. Within the stone are one or two seeds. Olives tend to have maximum oil content (about 20–30 percent of fresh weight) and greatest weight six to eight months after the blossoms appear. At that stage they are black and will continue to cling to the tree for several weeks. Fruits for oil extraction are allowed to mature, but, for processing as food, immature fruits are picked or shaken off the tree. Hundreds of named varieties of both types of olives, table and oil, are grown in warm climates. In California, olives such as the Mission variety are grown almost exclusively for table use. In Europe, olives such as the Picual, Nevadillo, and Morcal are grown mostly for oil.
Related Species: Wild Olive (Olea africana), Oleaster (O. europaea var. oleaster).
Distant Affinity: American Olive (Osmanthus americana), Fragrant Olive (O. fragrans).
Culture
Location: Plant olive trees in full sun and away from sidewalks to avoid stains from fallen ripe fruit. Non-fruiting trees are available which can be planted in areas where fruit may be a problem. Strong winds will "sculpt" the trees, but otherwise they are quite wind-tolerant.
Soils: Olives will grow well on almost any well-drained soil up to pH 8.5 and are tolerant of mild saline conditions.
Irrigation: Irrigation is a necessity in California with its dry summers. A monthly deep watering of home grown trees is normally adequate. Because of its small leaves, with their protective cuticle and slow transpiration, the olive tree survives even extended dry periods.
Fertilisation: Fertilising olive trees with additional supplies of nitrogen has proved beneficial. In California farmers systematically apply fertilisers well ahead of the time flowers develop so the trees can absorb the nitrogen before fruit set. Many growers in Mediterranean countries apply organic fertilisers every other year.
Propagation: 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 root stock.
Cutting:A commonly practiced method is propagation from cuttings. Twelve to fourteen inch long, one inch wide cuttings from the two year old wood of a mature tree are 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.
Climate:The olive 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. Home grown olives generally fruit satisfactorily in the warmer coastal valleys of California. Virtually all U.S. commercial olive production is concentrated in California's Central Valley, with a small pocket of olive acreage outside Phoenix. The tree may be grown as an ornamental where winter temperatures do not drop below 12° F. Green fruit is damaged at about 28°, but ripe fruit will withstand somewhat lower temperatures. 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. Olives can also be grown in a large container, and has even appeared in shows as a bonsai.
Pests and diseases: The olive tree is affected by some pests and diseases, although it has fewer problems than most fruit trees. Around the Mediterranean the major pests are med fly and the olive fruit fly. In California, diverticulitis wilt is a serious fungal disease. There is no effective treatment other than avoiding planting on infested soils and removing damaged trees and branches. A bacterial disease known as olive knot is spread by pruning with infected tools during rainy months. Because the olive has fewer natural enemies than other crops, and because the oil in olives retains the odour of chemical treatments, the olive is one of the least sprayed crops.
Distant Affinity: American Olive (Osmanthus americana), Fragrant Olive (O. fragrans).
History behind Olive
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 civilisation, its development being one of civilised man's first accomplishments. At a site in Spain, carbon-dating has shown olive seed found there to be eight thousand years old. O. European may have been cultivated independently in two places, Crete and Syria. Archaeological evidence suggest 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. There is some disagreement over when the trees first appeared in California. Some say they were introduced in 1769 when seeds brought from Mexico were planted. Others site the date 1785 when trees were brought in to make olive oil.
Flowers: The small, fragrant, cream-colored olive flowers 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.
Fruit: The olive fruit is a green drupe, becoming generally blackish-purple when fully ripe. 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. Raw olives contain an alkaloid that makes them bitter and unpalatable. A few varieties are sweet enough to be eaten after sun drying. Thinning the crop will give larger fruit size. This should be done as soon as possible after fruit set. Thin until remaining fruit average about 2 or 3 per foot of twig. The trees reach bearing age in about 4 years.
Foliage
The olive's feather-shaped leaves grow opposite one another. Their skin is rich in tannin, giving the mature leaf its gray-green appearance. The leaves are replaced every two or three years, leaf-fall usually occurring at the same time new growth appears in the spring.Flowers: The small, fragrant, cream-colored olive flowers 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.
Fruit: The olive fruit is a green drupe, becoming generally blackish-purple when fully ripe. 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. Raw olives contain an alkaloid that makes them bitter and unpalatable. A few varieties are sweet enough to be eaten after sun drying. Thinning the crop will give larger fruit size. This should be done as soon as possible after fruit set. Thin until remaining fruit average about 2 or 3 per foot of twig. The trees reach bearing age in about 4 years.
Growth Habits: The olive is an evergreen tree growing to 50 ft. in height with a spread of about 30 ft. The tree can be kept to about 20 ft. with regular pruning. The graceful, billowing appearance of the olive tree can be rather attractive. In an all-green garden its grayish foliage serves as an interesting accent. The attractive, gnarled branching pattern is also quite distinctive. 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.
Foliage
Culture
Location: Plant olive trees in full sun and away from sidewalks to avoid stains from fallen ripe fruit. Non-fruiting trees are available which can be planted in areas where fruit may be a problem. Strong winds will "sculpt" the trees, but otherwise they are quite wind-tolerant.
Soils: Olives will grow well on almost any well-drained soil up to pH 8.5 and are tolerant of mild saline conditions.
Irrigation: Irrigation is a necessity in California with its dry summers. A monthly deep watering of home grown trees is normally adequate. Because of its small leaves, with their protective cuticle and slow transpiration, the olive tree survives even extended dry periods.
Fertilisation: Fertilising olive trees with additional supplies of nitrogen has proved beneficial. In California farmers systematically apply fertilisers well ahead of the time flowers develop so the trees can absorb the nitrogen before fruit set. Many growers in Mediterranean countries apply organic fertilisers every other year.
Propagation: 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 root stock.
Cutting:A commonly practiced method is propagation from cuttings. Twelve to fourteen inch long, one inch wide cuttings from the two year old wood of a mature tree are 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.
Pests and diseases: The olive tree is affected by some pests and diseases, although it has fewer problems than most fruit trees. Around the Mediterranean the major pests are med fly and the olive fruit fly. In California, diverticulitis wilt is a serious fungal disease. There is no effective treatment other than avoiding planting on infested soils and removing damaged trees and branches. A bacterial disease known as olive knot is spread by pruning with infected tools during rainy months. Because the olive has fewer natural enemies than other crops, and because the oil in olives retains the odour of chemical treatments, the olive is one of the least sprayed crops.
Health Benefits:
Olive oil and the cardiovascular system
Olive oil is the main source of dietary fat in the Mediterranean diet. There appears to be a lower death rate from cardiovascular diseases in the Mediterranean area, compared with other parts of the world.
Olive oil intake also appears to help reduce inflammation, endothelial dysfunction (problems with the inner linings of blood vessels), thrombosis, and carbohydrate metabolism.
Frying with olive oil and heart disease risk
People who regularly eat foods fried in olive oil or sunflower oil do not have a higher risk of heart disease or premature death, researchers from Madrid, in Spain, reported in the BMJ.
The scientists surveyed 40,757 adults aged from 26 to 69 years over an 11-year period. They focused on cooking methods and dietary habits. None of the participants had heart disease when the study started.
Olive oil may help prevent stroke
Scientists in France concluded that olive oil may prevent stroke in older people.
The team found that older people who regularly used olive oil for cooking and salad dressing or with bread had a 41-percent lower risk of stroke, compared with those who never consumed it.
The researchers suggested that olive oil might be a cheap and easy way to prevent stroke, a common problem in older people.
Depression risk and olive oil
People whose diets are high in trans fats may have a higher risk of depression, compared with those whose diets are rich in mono- and polyunsaturated fats. Trans fats are widely used in fast foods and mass-produced items, such as pastries.
Olive oil may reduce breast cancer risk
Scientists from Barcelona in Spain found a key mechanism by which virgin olive oil protects the body against breast cancer, in contrast to other vegetable oils.
After decoding signals in the cells of breast tumours that are activated by virgin olive oil, they concluded that the oil reduces the activity of p21Ras, an oncogene. This oncogene prevents DNA damage, encourages tumour cell death, and triggers changes in protein signalling pathways.
Olive oil helps maintain healthy cholesterol levels
A Japanese study published in the Medical Science Monitor showed that LDL-cholesterol concentrations fell in 28 outpatients who took olive oil supplements once a day for 6 weeks.
Low-density lipoprotein (LDL) is often referred to as "bad cholesterol". The "good cholesterol" is high-density lipoprotein (HDL).
The authors concluded, "These results point to an overwhelmingly beneficial influence of olive oil on the lipoprotein spectrum."
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