Other Names: Azeitona, Aceituna, Olijf, Oliva
The olive is an evergreen tree growing to 15m in height with a spread of about 10m. The tree can be kept to about 6m with regular pruning. The graceful, billowing appearance of the olive tree can be rather attractive. 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.The olive's feather-shaped leaves grow opposite one another. Their skin is rich in tannin, giving the mature leaf its grey-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.The small, fragrant, cream-coloured 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. 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 flavour. 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. The trees reach bearing age in about 4 years.
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. Green olives and black olives are soaked in a solution of sodium hydroxide and then washed thoroughly in water to remove oleuropein, a naturally bitter carbohydrate.Then green olives may be allowed to ferment before they are packed in a brine solution. Black olives are not allowed to ferment before packaging, which is why they taste milder than most green olives. Green olives that do not ferment before packing taste as mild as black olives.
Olive 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. Delicate babies absorb its nourishing properties well through the skin. Its value in worms or gallstones is uncertain.Internally, it is a laxative and disperser of acids, and a mechanical antidote to irritant poisons. It is often used in enemas.
Olive trees like cool/cold winters and hot summers. Even though olives are evergreen trees, they still need a cool winter so they can rest to prepare for their main shooting, flowering and fruiting in the spring. For most varieties some winter frost is preferred.
Olive trees show a marked preference for calcareous soils, flourishing best on limestone slopes and crags though the tree will grow in any light soil, and even on clay if well drained. Ideal pH is 7-8.
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. 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.