Olive tree


(Genus: Olea europaea - Family: Oleaceae)

 

The Olive tree and its origins

Steeped in history and referenced throughout the ages, the olive tree is said to be the first tree selected by man.  This evergreen is a native of the Mediterranean and originates from the southern Caucasus region.  Olives have been cultivated for at least 7000 years; it is believed the tree was brought to the Mediterranean by the neighbouring Phoenicians.

This prized tree was considered sacred and its planting was strongly encouraged; for the ancient Greeks it made an important contribution to prosperity and a refined way of living, delivering fruits, olive oil and great wood for building.  In 1500BC, Minos, the king of Crete, developed olive oil production and it quickly became a highly desired commodity, exported at a high price to Southern Italy, Sicily and Sardinia.

Ancient olive trees have a large and twisted appearance, the older the tree, the more twisted its appearance and it can have a trunk circumference of 6m. Some of the most famous are the trees in the Garden of Gethsemane, on the Mount of Olives which are said to be 3000 years old and the Witches Olive Tree in Magliano of Grosseto, in Tuscany which is believed to be the oldest at 3,500 years old. 

 

How to Plant Olive trees

An incredibly hardy and very slow-growing evergreen tree, Olives can live for thousands of years thanks to their robust root system which is capable of regenerating. 

They thrive in a warm, temperate climate which is dry with very low rainfall and when exposed to full sunlight.  The tree is resistant to drought but the fruits can be affected if the soil is too dry.  Water logged soil and extreme drops in temperature can also harm the root system.  Olive trees will grow in most soil types but for best results, plant in a loose or medium textured soil which is well draining. 

Planting normally takes place in March.  Each tree should be allowed a spacing of at least 30-40m2 to ensure there is plenty of room for future growth.  The first fruits can be expected after 3-4 years. 

During the early stages of growth, nutrition is important, use 2-2.5kg of XXXX per plant to give the plant balanced nutrition for the first 4 months.  Alternatively, use XXX every 2-3 months. 

When transplanting the olive tree into its final spot, treat using 10-30g of the same XXXX at the base of the hole; repeat this action as you fill the hole, until you reach 40-80g per 60cm hole.

Another alternative for organic growth is Bayfolan Natra, which can be distributed at a dose of 7-9 kg per 100m². Bayfolan Natra is a pelleted organic fertiliser NPK mineral that only uses substances of natural origin and is approved for use in organic farming. Bayfolan Natra feeds the olive tree for a long time as it regularly releases nutrients and stimulates the soil’s micro-organisms. 

Irrigation is not essential but is recommended, especially in the early years after planting and during the summer, water shortages may reduce production.

Prune the tree in late winter before the plant begins to vegetate.  Fruit-producing branches that grow up to 25-50cm a year should remain, while non-fruit bearing and diseased or damaged branches should be removed to direct all nutrients to the fruit.  Maintain a balance between foliage and branches to ensure that the olive tree receives the full benefit of the sun. 

 

When to harvest olives?

Olives begin to bloom in April but the true flowers start to appear from late May to early June.  The flowers are small and abundant, they have a whitish colour, with 4 petals and appear in tiny clusters, of 10 to 15 flowers forming an inflorescence called "Mignola."

The olive tree has a shallow root system that needs loose soil to creep and establish itself.  The tree’s foliage displays in an irregular pattern with lance-shaped olive leaves that have a leathery texture and silver-grey appearance underneath with a green upper leaf.  

The trunk is made of a hardwood which is heavy and very fragrant.  In the early years, it will have a smooth grey bark and then becomes gnarled and dark as it begins to age.

The appearance of olive fruits will depend on the cultivar and the climate that it is grown in.  They are ready for harvest as soon as they turn green.  Olives left on the tree will ripen eventually turning into a black colour.  The majority are harvested in autumn and winter. 

Most olive cultivars are self-pollinating but it is good practice to plant more than one tree in your garden to aid pollination. 

Correct pruning is the most important factor to ensure a regular and consistent crop output.  Branches do not bear fruit in the same place twice and only appear on year-old wood; therefore, careful pruning must take place to encourage new shoots and a regular crop of fruit.  

 

Propagation of the Olive tree

Olives are most commonly propagated by cuttings or can be successfully grown from grafts.  Grafts tend to produce the best results; they are more resilient and hardy.

A slow growing tree, an olive will produce fruit in 3-4 years from the point of transplanting.    

 

Diseases and insects affecting Olive trees:

Olive fly

The olive fly is a parasite that affects the crop and can sometimes cause serious damage if it is not checked. This tiny insect lays its eggs and larvae inside the olives, causing the fruit to drop and a degrading of the quality of the oil by increasing its acidity. The optimum temperature range for development of this insect is between 20°C and 30°C. 

Treatment : xxxx can irradiate the olive fly, the new formulation controls the fly eggs and larvae. Apply a dose of x-x ml for every xxL of water to the olive tree.

 

Moth

Moth larvae are greyish brown and produce a first generation of moths that penetrate the olive tree’s leaves, the second generation attack the flower buds, destroying them and the third and final generation settle on the young oil kernel. 

Treatment: A traditional remedy is to use a xxx (x ml/xx litres of water) to eliminate moth larvae from the olive tree.  Organic farmers can treat the problem with xxxxx (xx-xx ml/xx litres of water).

 

Peacock

The upper surface of the olive leaves can develop a disease from which round spots, 1 cm in diameter, reddish-grey, with a dark edge and yellow halo colour develop. This results in strong winter defoliation.

Treatment: Traditional growers can use a treatment of xxxx (xx-xx ml/10 liters of water) in October and a second treatment in late winter to prevent this disease.  Organic farmers can treat the olive tree with xxxxxxx (xx-xx g/10 litres of water). 


Olive Tree Tuberculosis (Pseudomonas savastanoi)

A disease caused by bacteria, it occurs mainly on young olive branches and stems. However, it can also attack the leaves, roots and olives. The bacteria penetrate the plant through the injuries previously caused by weather damage, other pests or poor pruning methods with unsterilized equipment.

Treatment: To prevent the spread of the disease in the olive tree, only use sterile equipment when pruning and destroy any infected prunings.
Then treat the tree with a dose of xxxxxxxx (xx-xx g/10 litres of water), this product is suitable for organic farming.

Did you know: Use of olives and interesting facts

Referred to throughout the ages, there are many legends that relate to olive trees and it features regularly in the bible, including the story of Noah’s ark.  Noah sent a dove in search of land and the dove returned with an olive leaf and with the hope of land, Noah was at peace, the olive and dove became symbols of peace.

Olives are used widely in cooking from salads to sauces. They feature as a key ingredient in many Mediterranean dishes.   The health benefits of olives and olive oil is widely noted and has prompted the increase in growing olive trees for commercial production.