Everything you need to know about the Olive Tree

The olive tree is the fruit tree of the Oleaceae family from which the oil comes, the olive juice that we use to make our meals, to dress salads and to make a multitude of products. Thanks to all these uses, the demand for the olive tree continues to grow at exponential rates, with Spain and Italy being the main producers.

The olive tree is native to Asia Minor and has been cultivated since ancient times throughout the Mediterranean basin. The wild variety is called olive border or acebuche.

Despite being a very resistant tree , the reduction of water or mineral nutrients just weeks before the flowering season can result in less flowering and, consequently, in fewer olives.

Olive trees adapt quite well in the Mediterranean regions and those close to the Aegean Sea due to their salinity, temperature and humidity conditions, however, they are not elusive in these areas since they also do quite well in other regions.

Types of Olives

The first thing you should know about olive trees are of two types: those with green olives and those with black olives , contrary to the popular belief that there is only one type of tree and that the fruits change color depending on their degree of maturity. mature.

First let’s talk about green olive trees , these will bear fruit at the end of summer or beginning of autumn, if harvested in this season, green olives can be prepared to be consumed directly, although if they are not harvested, olives can be leave up to one more year before being harvested, they will turn black and will be a very good fruit for the manufacture of olive oil although they are not suitable for direct consumption.

As a second point we have the harvest of the black olive trees , these, like the green olive trees, will bear fruit at the end of summer or beginning of autumn, however, the harvest must be harvested immediately regardless of whether they want to be used. to prepare and consume them directly or if they are going to be used for the preparation of olive oil.

The olive trees of the two types reach maturity two years after being planted, they generally measure around one and a half or two meters and begin to bear their first fruits in summer; The young trees bear better quality fruits due to their flavor and size. They are generally used for consumption. When the trees age after 10 to 15 years, the fruits are reduced in size and are used for oil production.

Olive trees do not grow from the seeds of olives, they require special care at the beginning, so they can be purchased at a specialized store where they have grown in-vitro or they can be planted by root or by means of a branch to be cut diagonally from a mature tree no older than 10 years. It is recommended to plant the new bushes in autumn due to the humidity of the soil and the climate.

The pruning of the olive trees must be done after the harvest at the beginning of winter, this is a fundamental process to guarantee an abundant production at the end of the following summer, otherwise, the nutrients will be dispersed in the branches and leaves, giving poor fruit.

We recommend you read our post Olive grafting , so you can learn a little about this particular fruit tree


The olive tree is an easy-to-grow tree that does not tolerate temperatures below -10°C but is quite suitable for combating the winter frosts typical of the Mediterranean climate and the summer droughts that are getting longer and longer. The climatic component that most damages this fruit tree is the wind.

vegetative structure

It is an evergreen tree with the ability to live and produce for hundreds of years. It has medium size: it is between 2 and 10 meters high.

It follows a corm vegetative structure, formed by: root, stem (trunk) and leaves. The root, in the case of trees born from seed , is axonomorphic and has a pivoting character, that is, there is a main root that penetrates the earth without branching. When the tree comes from cutting rooting , instead, a set of secondary roots are formed. In both cases, however, small roots grow continuously, which are the ones that most easily absorb nutrients. The depth to which the root reaches depends on the structure, fertility and humidity of the soil.

The trunk is tortuous, thick and branched. The bark, in young specimens, is smooth and light gray in color, and over the years it fissures and darkens. The wood is hard. The cup is rounded, tight and irregular. The leaves are simple, coriaceous and lanceolate, with entire margins and an acute apex.

They are arranged in the opposite way and are persistent, that is, they do not usually fall until two or three years after their formation. The length varies between 3 and 8 centimeters, and the width, between 1 and 2 centimeters. The petiole is short: about 0.5 centimeters. The front of the leaf is dark green, with a certain shine due to a cuticle that is not very permeable to water, typical of plants that, like the olive tree, are xerophilous . On the reverse, on the other hand, the leaves are silver-gray green due to the presence of numerous protective hairs called trichomes that cover the stomata, which are only found on this lower part of the leaf, and prevent water loss.

reproductive parts (flowers)

Olive blossoms begin to bloom in late March, but the true flowers come out in April or May. They are small and actinomorphic with radiate symmetry. The corolla is white or yellowish white, with four petals welded at the base, that is, it is gamopetalous. The calyx is small and formed by four welded sepals (gamosepalus). The androecium is formed by two stamens welded to the petals. The gynoecium is bicarpelar, that is, formed by two welded carpels that form the pistil, which is composed of a superior ovary, a short style and a bilobular and papillose stigma.

The flowers are inserted in small, axillary paniculate inflorescences containing 10 to 40 flowers .

There are two types of flowers: the perfect ones and the staminiferous ones. Perfect flowers are hermaphroditic, that is, they contain both sexes, and this is made clear by the presence of well-developed stamens and pistils. Staminiferous flowers, as their name suggests, only have stamens and, therefore, are male flowers and will be unable to produce fruit. The staminiferous flowers are found on the tree in variable proportion; in conditions of strong drought they are the only ones that appear, and in this case there is no production of olives.

The formation of the flowers begins in the autumn of the year before flowering.

The fruit

The fruit of the olive tree is the olive. The pollination process to allow the flowers to fruit is similar to that of any angiosperm: one of the two male gametes in the pollen tube unites with the ovule and the other with the polar nuclei. We can also obtain fruits by parthenocarpy, but, in this case, the olives, which have been formed without a process of fertilization of the flower, are very small in size. Generally, this pollination is carried out by the wind , since it is an anemophilous plant, but sometimes insects also participate in this process.

The olive is a small drupe fruit that has an ellipsoidal or globose shape that is more or less symmetrical. It has the seed enclosed in a hard endocarp that forms the bone, which solidifies 4 to 6 weeks after the start of fruit formation and hardens up to 3 months later.

The mesocarp continues to grow throughout the season. Fruit growth shows a double sigmoid growth curve as occurs in most drupes. The seed reaches maturity just before the fruit changes color in the so-called ” green ripening ” stage. Fruit growth stops when the fruit begins to change color. after the green ripening stage there is a decrease in the chlorophyll content and an increase in the accumulation of anthocyanins responsible for the black color of the fruit . Its color can take on different shades, ranging from green to red, but when it matures it turns black.

It normally measures 1 to 4 centimeters in length and 0.6 to 2 centimeters in diameter, depending on the variety. The percentage of oil content varies according to the cultivars between 12 and 28%. Per hectare you can have 22,000 kg of olives. The weight of the olives varies between 1 and 12 grams depending on the varieties. For example, the olives of the Koroneiki and Arbequina varieties are very small and the Gordal and Ascolana are very large. The fruit is divided into endocarp (bone), mesocarp (pulp) and exocarp (skin). The endocarp is made up of a single hard, ovoid seed. The storage of the oil is carried out in the parenchymal cells of the mesocarp.

Vegetative cycle

The olive tree presents the contranñada phenomenon in a very pronounced way and has a natural tendency to produce every two years. The production happens slowly and progressively, but in a lasting way between 1 and 7 years. This is the period of unproductive installation, the duration can be doubled in case of a dry season. Up to 35 years the tree develops and experiences a progressive increase in production; between 35 and 150 years, the olive tree reaches full maturity and its optimum production , and, after 150 years, the tree ages and its yields are random.

olive tree physiology

The olive tree is probably the most resistant to cold among subtropical fruit trees . It is the sclerophyllous and glycophytic species (glycophytes are the non-halophytic plants) more tolerant to salt and drought than other temperate fruit trees. Some authors include the olive tree in the category desert shrubs . It is also the only oleaceae with edible fruit. Cultivable on a wide variety of soils, even thin and poor quality ones. The pH range possible for the soils where the olive tree is grown is from 5.5 to 8.5 with the optimum between 7 and 8. Only poorly drained compact soils are limiting due to the sensitivity of the olive tree to hypoxia (which suffocates the roots ).

drought resistance

Under conditions of high air vapor pressure deficit (Da), olive trees avoid excessive water loss by closing their stomata. The current year’s leaves have better stomatal control than the previous year’s. Rainfed olive trees recover quickly after the dry summer season, showing physiological values ​​similar to those of irrigated olive trees two days after the return of the rain.

The leaves and the crown : The leaves are adapted to avoid excessive water loss. In addition to having sclerophyll characteristics, it has mechanisms that control water loss. The tree has leaves up to three years old. With age, the characteristics of the leaves and the response to the environment are modified.

Perspiration occurs only through the stoma while cuticular wax prevents it through the cuticular membrane. In addition, the mesophyll layer is densely packed, leaving little surface area of ​​cell walls exposed to the air.

Photoperiod and temperature

This plant does not respond to photoperiod (it is a day-neutral plant). In some crops, 1,000 hours are needed below a temperature of 7 ° C. The olive tree begins to form flower buds at the end of winter, approximately 8 to 10 weeks before full flowering in response to the progression of temperatures. wintery Exposure to a constant temperature of 12.5 °C results in significant flower production.

This temperature is called the “compensation point” and is believed to be sufficient for vernalization but also warm enough to allow concomitant cell division. The olive tree needs at least 10 weeks below 12.2 to 13.3 for the full expression of flowering , it is best induced when the temperature fluctuates between 2 and 15 for 70-80 days. That is why in hot tropical climates olive trees never flower . The effect of extreme temperatures (strong frosts and excessively high temperatures) must be taken into account. The plant can suffer severe damage with -12 °C or higher temperature if the exposure is prolonged.

ancient olive trees

In the world there are at least 17 species of trees that can live more than 1000 years, almost all of them are conifers and the oldest known are pines of the species Pinus longaeva that live in the Rocky Mountains with ages close to 5,000 years . Several large olive trees from the Iberian Peninsula and other areas of the Mediterranean Basin are popularly known as ancient olive trees. Some of these olive trees have been estimated to be 2,000 to 2,500 years old.

Determining the age of olive trees by means of tree growth rings is more problematic in olive trees than in many other trees since these rings are not very distinguishable in olive wood, due to the functioning of their asymmetric cambium and the maturation process of the wood, do not follow a known temporal pattern to this is added the fact that the olive tree can be too crooked. The age of the roots of the olive tree may be greater than that of its trunk.


Olives (fruit), as well as the oil obtained from their pressing, are very common elements used in the Mediterranean diet.

The olive is a food with great nutritional value that contains few amounts of sugar and is usually eaten in appetizers and salads.

Olive oil is the differential element par excellence of the Mediterranean diet. It is used both for dressing and for frying food. Its lipid composition provides certain fatty acids that are essential for our body and helps some vitamins to be absorbed by the human body.

History and traditional uses

The olive tree is a plant present in many cultures. In Ancient Greece, for example, olive oil was considered sacred and was used to anoint kings and athletes. The leafy branches of the olive trees were a symbol of abundance, glory and peace and were used to crown the winners of friendly games or wars.

According to the mythology of this area, the olive tree was a gift from the goddess Athena to the people of Attica. We also find the olive tree present in the Egyptian culture where its branches are a symbol of blessing and purification and we find them in the tomb of Tutankhamun.

n Rome, the poet Horace mentions the fruit in reference to his own diet, which he describes as very simple: “For me, olives, escarole, and mauve.” Lord Monboddo comments that olives were, in 1779, one of the favorite foods of old people.

The olive tree is one of the most cited plants in the literature. In Homer’s Odyssey, for example, Odysseus crawls under two olive shoots.

The olive tree also has an important role in the Bible where it is mentioned more than 30 times in both the Old and New Testaments. For example, it was an olive branch that showed Noah that the flood was over. Moses also handed over military services to those who cultivated olive trees. The Qur’an also mentions the olive tree.

This fact of finding the olive tree so present in the different Mediterranean cultures and in literature is due to the places where this tree has appeared. The cultivated olive tree (the wild olive tree has been a naturalized plant for millennia) appeared in the Mediterranean region a few thousand years after its place of origin, the Middle East, some 7,000 years ago. In the Peloponnese, olive cultivation began around the 3rd century BC. After the 16th century, Europeans brought the olive tree to America. Mainly in California, Mexico, Peru, Chile and Argentina. There are also small plantations in China, Japan and Nepal. It is estimated that there are currently about 800 million olive trees worldwide.

Olive trees produce some of the most desired fruits in the world, olives, these are used for the preparation of one of the finest and purest oils due to its low acidity, a characteristic that makes it highly appreciated and healthy; olives can also be consumed directly, these fruits are seasonal although they require prior treatment and preparation that seek to reduce the bitterness of the fruit in order to be consumed.

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Robert Asprin, APD is a non-dieting Accredited Practicing Dietitian passionate about inspiring positive changes in eating and lifestyle behaviors to help improve health while nurturing relationships with food and body.

Robert Asprin

Robert Asprin, APD is a non-dieting Accredited Practicing Dietitian passionate about inspiring positive changes in eating and lifestyle behaviors to help improve health while nurturing relationships with food and body.

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