Garden

Olive trees - Olea europaea


GeneralitŠ°


The olive tree is a small tree, originating from the area around the Mediterranean Sea; the botanical name is Olea europaea, and it is the only species of the genus whose fruits are used, while of some other species (Olea capensis, Olea laurifolia) they are cultivated for their compact and heavy wood, of excellent quality. Being small trees naturally present also in Italy, any fan of plants and gardens knows well the salient features of the olive tree: it is a fairly small tree, which does not exceed 6-8 m in height, very long-lived, with a stocky trunk, gnarled and twisted, and sparse ramifications, which give rise to a disordered crown; the leaves are small, lanceolate, evergreen, coriaceous, with the upper page green gray, and the lower page light, gray. The general appearance of an "old" olive tree is that of a plant that struggles to survive, even if in reality this aspect is maintained even in the specimens that have everything they need available; It is a distinctive trait of olive trees, which makes them very interesting in urban furnishings and in the preparation of gardens. Older, large olive trees, which can count on several decades of life, can reach very high prices, and for this reason many people consider a large olive tree in the garden a sort of green status symbol. Unfortunately this feature has led many plant traders to look for more and more ancient olive trees, to be explanted and sold, thus plundering the olive groves of some areas of the Mediterranean from the most beautiful specimens. In some Italian regions, efforts are now being made to protect the dignity of these trees, trying to recover uncultivated and abandoned olive groves, so that the olive trees they contain are not sold to the highest bidder as garden plants. The olive trees produce very small white or greenish flowers, which bloom on young twigs, called mignole, produced at the leaf axil; the flowers are followed by fruits, small oval drupes, called olives, which are used for direct consumption or to produce olive oil, one of the healthiest and most valuable oils. The olives have a thin green flesh, which becomes purple or purple when ripe, in October or November, the maturation of the olives is called veraison; in Italy usually the most aromatic and delicate oil is extracted from partially unripe or not yet fully ripe olives.

The olive varieties




Thus, the olive trees all belong to the same species, olea europaea; the other species of olea do not produce drupes from which an edible oil can be obtained; for this reason there are no different species of olive tree; there are some subspecies, widespread in South Africa and in the Canary Islands, but in general edible olives and oil are obtained only from trees of the olea europaea species. These trees have been grown in the Mediterranean area for millennia, and olives are mentioned in writings from ancient Greece and even earlier; the trees are very long-lived, there are specimens that count more than a thousand winters; millennia of man's cultivation, and the diffusion (quite "recent") of these trees also in other areas of the globe, such as Asia and South America, have given to an incredible quantity of cultivars, only in Italy there are some three hundred. The wild olives produce small fruits, with a thin and firm flesh, of little interest for the consumption or the production of the oil; over the millennia man has selected those specimens that for some reason produced larger and more fleshy fruits, and propagated them, grafting them onto other specimens, or through cuttings, thus maintaining the most interesting features. Despite the existence of so many varieties of olive cultivar, most people know only a few, less than a dozen, because they are the most widespread, or because they are linked to particular food specialties. The cultivars widespread throughout Italy are Leccino and Moraiolo; then there are various other cultivars that differ from region to region, and also depending on the use that is made of olives; the Taggiasche olives are typical of Liguria, the Rosciola olive is typical of Molise, the Bella olive of Cerignola is cultivated in Puglia; and so on. Among the non-Italian cultivars perhaps the most famous in Italy is the olive from Kalamata, cultivated in Greece. These varieties have larger fruits, but sometimes also simply fruits that give rise to an oil with a particular aroma, which then becomes typical of the region of production; who habitually consumes extra virgin olive oil, knows also the great differences that can be had, for example, between the Sicilian oil and that Ligure; this difference is due essentially to the different cultivars that are cultivated in the two different regions.

Cultivate the olive tree



The olive tree is a Mediterranean plant, which is well suited to living in most of Italy, especially in areas with mild winters; it bears heat and drought very well, even if, in olive groves, water stress can cause a noticeable drop in production and fruit size, with obvious damage to the consequent production of oil. Olive trees also tolerate cold quite well, but they do not tolerate temperatures below -7 / -10 °, especially if they occur for long periods of time. They are therefore grown in sunny places, possibly with not too cold winters, or in any case sheltered from the cold winds of December and January. The production of the first shoots usually takes place in late winter, between February and March, so it is clear that in areas with very cold winters the production of flowers and fruits will be very low. The olive trees produce a broad, but shallow root system, which generally stops at a depth of about one meter; therefore they do not need excessively deep soils, and develop best in stony, fairly rich, but very well drained soils. They especially fear compact and heavy soils, with even occasional water stagnations; in some areas of Italy olive trees do not withstand winter due to excessive winter humidity. At planting, therefore, tends to enrich the soil with manure, and to make it more draining by adding sand, pumice stone or gravel, so that the risk of stagnation is minimal. If we live in an area with very cold winters, and with strong humidity, it is advisable to place the olive trees, during the winter months, in a place sheltered from the cold and rain, then growing them in pots, or preparing a sort of cover on the plant . In the winter months the olive trees are in a phase of vegetative rest, and therefore do not need watering.

Water the olive trees




Olive trees are not particularly demanding as far as watering is concerned, and they can withstand months of drought, without suffering too much; clear that, a long period of drought can cause very few fruits or very small fruits. In winter the watering is not necessary, even if, at the end of winter, when the future buds are being prepared, the olive trees prefer a cool and humid climate. In addition to this, the second important moment to have a good harvest and a luxuriant olive tree is the end of summer: the olives are present on the tree already in spring, in summer the development of the fruits stops, and hardening occurs of the hazel, which lasts until August; when the stones are lignified, the fruits begin to grow again, at the end of the summer; if in this period (late August-September) there is a period of strong drought, the olives stop developing, remaining with a thin and not very fleshy pulp. It is therefore important that the seasons take place in the best possible way, with good rainfall from late winter to spring, and from late summer to autumn. If these two periods of the year are particularly dry, it will be necessary to periodically water the plants, especially if they are fruit plants and not ornamental ones. Watering can be important even in the case of a young specimen that has recently settled down, especially in spring and summer, when the weather is very hot. We will water until the soil is well wet, but a second watering will be provided only when the substrate is definitely very dry.

Pests and diseases



Olive trees can face many parasitic problems, although cultivars that are particularly resistant to the most common diseases are being cultivated more and more often. The most known and widespread diseases are the peacock eye, a fungus that causes particular speckles on leaves and branches; wood decay, which affects wood close to pruning or tearing cuts caused by bad weather; radical rot due to heavy soil or water stagnation; olive rot, caused by a fungus that attacks the fruits, which can also be ruined by olive flies, which lay their eggs on the holes, and develop inside fruits, ruining the pulp; the cochineal half grain of pepper nestles on the leaves and on the young branches; oziorrinco, various types of thrips, beetles. There are many parasites that can attack an olive tree, and some also worry those who simply have an ornamental olive tree. Typically one tries to cultivate resistant varieties, and to cultivate the plant in the best way, so that it can defend itself independently from the attack of parasites. Clear that the use of cupric products at regular intervals can effectively prevent pests from approaching our olive tree. It often happens that an inexperienced grower cares about the drop of flowers on his olive tree; in fact the olive trees present some difficulties of fruit set, that is it is necessary that the flowers are well pollinated because they go to fruit, for this reason every plant produces a great quantity of flowers, many of which will never be fruitful, as they serve only and exclusively to pollinate the right amount of flowers. It is therefore normal, that in spring the olive trees lose most of the flowers; often in production olive groves fruit set is favored by planting olive trees of two different varieties, so that they act as pollinators of each other; this practice often favors the harvest.

Prune the olive trees




If we wish to collect the olives of our olive tree it is necessary to prune it in a suitable way, so as to favor the development of a large number of flowers, and consequently of fruits. The fruits of the olive tree are produced on the branches of the previous year, therefore the pruning must tend to favor the development of new branches and also the growth of the small branches already present in the foliage, so as to favor a constant production of olives during the years. Typically in olive groves the plants are all pruned following a chosen shape, dictated by tradition, by the climatic requirements of the area, by the type of harvest that will be carried out; there are therefore pruned olive trees in a vase, a polyconic vase, a palmette, a ypsilon, a bush; typically these terms indicate a very precise form, which is inspired by the shape of the future crown of young olive trees; an olive tree of about ten years should already have such a well-structured shape, which is usually intended to favor the growth of some supporting branches, which face outwards, with the inside of the foliage quite empty and well lit. In the subsequent interventions of pruning it goes to free the inner part of the foliage from the branches grown horizontally, crossed or in any case towards the inside; we also try to keep the trees fairly contained in height, to favor the work of the olive pickers, and in addition to this we regulate the development of the suckers, or of those branches that tend to develop upright upwards, which must be kept in minimum number. The final result is usually a well developed and disciplined crown, with many small branches, facing the outside of the crown, and downwards, and a few carrying branches, of medium-large dimensions. In the case of decorative olive trees it is not necessary to carry out this type of pruning, which essentially has agronomic needs, not related to the health or vigor of the trees: it is sufficient, periodically, to remove the broken or damaged branches, and to empty the foliage at the points in which is impenetrable by sunlight. Unfortunately it happens more and more often to see decorative olive trees pruned in the typical forms of olive groves, in a completely useless way. When an ancient olive tree is removed from the ground, it is necessary to make a good part of the root system; for this reason we plant the plant, that is we cut off most of the length of the bearing branches, to avoid that the plant suffers excessively; unfortunately in many gardens there are pollarded olive trees, which are recapitulated over the years, as if the practice had to be repeated even after the olive tree was moved, or as if the shape caused by the needs of the explant was the best for the tree itself.

Fertilizing


before planting it is preferable to give a good fertilizer based on manure and mineral fertilizers.
At the beginning of spring, it is good to give a good complete mineral and organic fertilizer.

Multiplication


generally it is not carried out by seed since the plants obtained grow slowly and do not bear drought. Sowing is used only to obtain plants to be grafted. Generally the multiplication occurs in various ways: by cuttings, using twigs of four five centimeters in diameter and forty centimeters in length to plant in pot with universal soil that must be kept humid but well drained. Another method of multiplication is to use rooted suckers formed from the eggs present on the plants; these are planted in the nursery and cultivated for some years.
The frank and the oleastro are used as rootstocks to obtain olive trees of selected varieties. The grafting can be done in spring with a vegetating bud or pike beak.

Watering


the olive is a crop that grows quietly in dry conditions but lately it is irrigated to obtain better production. Watering must be regular, even if not abundant (drop-shaped, with a micro-rain), allowing the soil to dry between one irrigation and another.

Pruning


the ornamental olive tree is pruned when young, giving it a harmonious shape, over the years dry or sick branches are eliminated.
The production pruning, taking into account that the olive does not tolerate the cuts well, must be limited to eliminating a part of the branches that have given fruit and to thin the young branches.
For the variety of table olives, thinning of the fruit is useful, which allows to obtain larger fruit and limits the phenomenon of alternating production.
Reconstitution or rejuvenation pruning is widespread, which consists in renewing older plants by growing new branches in place of exhausted ones.

Olive harvest


harvesting can be done by hand by shaking the branches and fronds with poles, dropping the fruit on nets previously laid under the plants. The fruits must be kept in not very thick layers and in a well-ventilated room. The olive tree bears fruit after a few years of training pruning, but the best yields are when the plant is adult.

Pests and diseases



the large olive cochineal infests the branches and leaves by sucking the sap and causing the formation of sugary substances that favor the fumaggini.
The olive fly, in the state of larva, damages the fruits that wrinkle, rot and fall.
The olive peacock's eye that shows itself with gray spots, red in the center that then become brown so the leaves fall and the production is scarce.
The mange of the olive forms on the branches of the growths that swell and bring the branch to death.

Olives: Olivo leccino



The leccino olive is a special olive cultivar, much appreciated for its aesthetic value and for other aspects that make it very suitable for cultivation for the production of olives. The olive leccino in fact, in addition to discreetly resisting at low temperatures, is a plant with good fruiting that produces a constant and consistent amount of olives.
The leccino also has an aging of the olives which is precocious compared to the other varieties but above all it is contemporary, an aspect to be taken into consideration in the organization of the harvesting operations.
The type of oil that is produced with this olive tree is a good quality oil, characterized by good fragrance, freshness and a slightly fruity flavor when the olives are harvested early, while an oil is obtained that is lighter, rounder and sweeter when the olives are harvested late.
The origins of the leccino are Tuscan and even if it is a resistant olive tree, it must always be positioned in a lighted place with drained soil, without water stagnation.
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