Po' Petroso Olive Oil

" We always try to do our best "

About Olive Trees

I make a preliminary statement. Please don't consider me a real expert in olive trees planting. This memo is far to be the Gospel according to St. Matthew. I own a little farm in Umbria, Italy, and in 1994 I planted only 500 new olive trees, according to most modern specialized systems, on about 4 acres.
Since many people all around the world seem to be interested to the matter, I thought to come into play and tell you about my most recent experience with the following notes about:

Olive Planting

The ideal sole for olive tree is the argillaceous one; but this kind of tree grows everywhere; my grandfather and father had a very large planting in north Africa,Millenary Olive TreeLibya, on the arid sand; and I personally saw still good millenarian planting among (but it is more exact to say "in") the rocks in the dry Spain.That means a minimum average annual rainfall is not necessarily required .
(This olive tree is more than 2.500 years old and grows in Fornalutx, Mallorca island.)
today, trickle irrigation is very diffused in olive planting.More and more farmers use it. I don't, and that, for many reasons: the above mentioned fathers experiences; olives for oil producing must be dry; if you water the plants once then you must water always; and so on. There may be, perhaps, convenience if you produce olives for bottling: the larger they are, the richer is the harvest! Anyway, olive trees fruit well after three, four years they have been planted.
The benefits of irrigation were studied some years ago in a Tuscanian intensive olive grove. In this test were confronted watered plants with not watered plants of the same cultivars.
The results: The fruits pertaining to the watered plants have shown a greater fresh weight, a greater dry weight, a greater volume but .... there were not found meaningful differences in the oil content between fruits pertaining to the two theses (“watered” and “not watered”). To such purpose it must be kept in mind that the oil content derives from the "inolizione" process which is the terminal stage of the development of the olive fruit.

Weather: we already accertained the olive's tree resistance to hot weather. But what about frost?
Olive trees are relatively affected by frost; they don't support too cold temperatures; by too cold I mean -20, -30 degrees centigrades. This winter was a hard one in Italy; we had minus 10 degrees centigrades but we had no damage at all. In 1985 we had a catastrophic winter, 28° centigrades below zero and most of the trees were destroyed. But careful: their roots never (or very seldom) die and they throw new good suckers !! It's therefore very important to plant scion trees so you will never need to graft them again.

The plant must be very young, one, better two years old (that means 13/25 months). The cost is lower, the taking of root surer and the growing is faster. At this proposal consider that only two plants of mine died in the meantime.... one of them caused by a wild boar that bared its root !!!

Planting way : the graphic shows the most rational, modern way of planting.The ground must be broken for a meter, not less; the trees must distance exactly 6 meters one from another; and the soil should be as plane as possible to facilitate the mechanized working process.
The young plants must be protected with woody bolts which must be set always to north to defend the trees from the cold wind and ten centimeters of distance from the trunk. The binding must be very wide. The height of the bolts must be inferior to the height of the scaffolding because the function of the bolts must be only a support. The binding must be preferably of elastic material to avoid any nesting of harmful parasitics.

Operation schedule : you must use a pruning shredder with a tractor twice a year to destroy the grass: in may and July. You need to hoe around themy olive treetrees once a year too, in June for example, to let the plants breathe. Some urea fertilization is suggested beginning after two or three years from planting, in April.
For planting large extensions, modern criteria require mechanized pruning (trees must be kept mono cones) every two years and mechanized harvest (hopefully every year!) .

Pruning : the ideal olive tree in Umbria does not grow as mono-cone; it has four main branches which form a sort of chest. As you can see in the picture the pruning idea is to open the tree to let the sun well lights the fruits and the foliage inside and to reduce the height of the tree to get picking operation more easy. We use to prune our trees every year: that's the best way to avoid alternate bearing. My trees have at least four branches, as I pick olives by hand with special combs.
Choice of the trees : I have the following six different cultivars to get dop quality : moraiolo,frantoio, maurino, leccino, pendolino and coratina ;for best success I think you should seek for information about the quality farmers use in your neighborhood.
Birds ? No serious problem; starting for the principle that fruit is bitter, birds generally don't use to eat olives; but a flight of thrushes can strip a tree of all its fruits in only a few minutes ! It seldom happens.

Olive bottling :If you are going to privilege the olive bottling rather than oil bottling, you must consider that the sort of plant you need requires warm climate and fertile ground . The fruit is more voluminous, with scarce oil contents and it is generally destined to be dried or picked.
Most famous ones are the olives of Greece, the Manzanillas of Spain and the Ascolane of Italy.

Manual and mechanized harvest

  • Browsing:it's the most rational method as you can send to the mill entire olives, without the presence of extraneous bodies -especially earth- that confer the oil acidity and unpleasant tastes. This method is applied with advantage in the planting with trees by low form and requires the use of fit equipments to effect a kind hair-style of the plants with fall of the fruits on synthetic nets on purpose extended around.

  • Knocking down : the harvest is effected knocking the branches with long poles of wood. The olives fall on the nets. The method is not recommended as both the olives- with consequent oil production of very bad quality- and the branches are damaged.

  • Picking up : Very diffused method either in really uncomfortable zones or when the trees are of remarkable height . The olives are picked up directly from earth after their natural fall. The harvest is effected some more or less long intervals . The product has scarce commercial value; the olives will be in fact damaged, dirty of earth and certainly afflicted by harmful fermentation processes; the harvest is not edible and must be destined to the refineries.

Mechanized harvest : The mechanized harvest is a valid remedy to reduce the costs of production and get esteemed oil to competitive price .hardpicker Numerous types of Italian or American manufacture shaker apparatuses (like the Shock Wave Shaker) exist on the market. These apparatuses are generally climbed on 70-80 HP tractors; they are hooked to the plants by different types and forms of pliers or rubber rolls and they engrave to the plants and to the fruits pendulum like or rotatory movements. The movements are brief and violent: so much that the drupes are easily detached from the trees and fall in the underlying nets. The process of the harvest is generally completed with use of aspirator apparatuses.

It's also possible to resort to new "soft" olive picking machines , also suitable for walnuts, almonds, pistachios and coffee.olipicker They looks easy and efficient in picking operations and assure quality and integrity of fruits, safety for trees, return on investment for farmers. Their articulated lifting equipment with independent and tilting support allows no stop rotation 360° , variable length of second arm, pick-up rotation 300°, around the second arm.
Their hydraulic plants are driven by tractor engine; they have 83 pair of brushes made in thermoplastic material. This satisfactory range of movements allows the pick-up to operate up to 8,50 mts high from earth to 4 mts depth from earth.
Another more simple manual "soft" olive picker consists of a pneumatic comb assembled on variable manual-pickerlength rods (from 2,50 mt to 3 mt). It's able to pick fruit to a height of 5/6 metres. It's operated either by a single silent  electrical battery or by a much noisier compressor  applied to the three points of a tractor or to a motor cultivator. When joined to compressor, the "olive picker" can use up 200 l/minute of air and is able to pick 10/12 q a day of olives for every operator. Thanks to the possibility of extension of air tubes, you can reach impassable zones as terrace cultivation, slopes, etc, which were so far inaccessible to any mechanical means. According to the power of the compressor, from 2 to 8 olive pickers can simultaneously work.

The following table shows the productivity percentage according to the different picking systems :

Fruit-detaching yards

(olives' retrieval and nets' movements excluded)
Picking System Workers

Olives Kgs/h
per each worker

manual 4 17
pneumatic comb 2 84
"soft" olive picking machines 1 185
shaker apparatuses 1 635

How to store the olives
: to get an oil of best quality it is advisable to grind the olives within brief time, maximum 1- 2 days from the harvest. But not always the oil mills are able to grind the daily delivered consignments. Therefore it can be necessary to store the olives for some more days. This is a very delicate moment, because it is necessary to prevent the natural chemical modifications that bring to an increase of the degrees of acidity and oxidation of the oil. The best conditions for the maintenance of the olives are the followings:
  • low temperature, 10 - 15 centigrade degrees;
  • low relative damp, not superior at 50 - 60%;
  • storage in thin layers with good circulation of air between the different layers.

A rational system consists in the realization of layers of non superior height of 10 - 12 centimeters. Such disposition can be done on the floor or better using hurdles with looms that are to be superimposed one upon another. Such structures consent a notable economy and a better circulation of the air. Alternatively you can resort to the use of perforated plastic cassettes taking care to avoid to fill them up more than 20 - 30 cms.
However, remember that less time you have to storage the olives, the better it is for the quality of your oil.
The following table shows the percentage of decrement of the quality in relation of the length of the storage time:

Storage Time
( days)
Aromatic Quality
Aroma's Decrement
( per cent )

Mill : the stone mill and cold pressing technique, as better showed in the followingmill animated graphic, are suggested for the extraction of extra virgin olive oils .
The leaves are firt sucked away by air fans and the olives are washed with circulating potable water to remove all impurities. The second step of extraction is crushing the olives to form a paste. The olives are collected in a crusher where the oil sacs are broken perfectly : the crushing of the pits is finely calibrated and finished with two granite millstones. The resulting paste falls into the kneading machine, with 2 stacked modules. Here the right heating temperature and the helical shaped blades ensure that the paste is processed perfectly. The heating ( about-28 degrees Celsius ) is provided by the circulation of thermostatically controlled water through the cavity in the wall of the kneading machine. The olive oil is then pumped into a separator in order to separate the oil from the water and small solid particles.

Maintenance of the oil of olive : the choice of the correct container and of the correct environment is fundamental ; modern containers are made of glass or of steel (once they were made of earthenware). It must be preserved to the dark and to a mild temperature; the light favors the rancidity of the oil. The oil maintains intact the own organoleptic characteristics also after three years.
Propagating : if you need to replace some trees you can try to propagate them from the olive trees you already have. Therefore you can use your pruning branches. According to prevailing theory it's better to use woody scions, 2-3 years old, about one inch wide, each one 8-10 inches long. After removing all the leaves you must put the branch in a horizontal way a few inches under the ground. It will germinate several lateral shorts in a few months. Each short will be a new plant.
Someone tried also to cut a one year old olive branch, with no less of 3/4 gemmas sticking it in agri-perlite's layer; the branch should take roots in a two/three months; but it is subject to frequent nebulizations: so it's better if you have a greenhouse with sprinklers.
In somebody's opinion the best way of propagating is directly by stones coming from very mellow olives; after you have removed grease and bathed them for a few hours in a lye (sodium carbonate or ash mixed to lime) solution, you must stratify them in the sand; the stones must then be kept in a dry room.propagating
Sowing is generally scheduled in June, July or August; in a cold bed preferably inside a large masonry case. It's better to crack carefully first the stones with the hammer.
Seed germinates in about 40-50 days; as soon as plants have 4-6 leaves, on March, they will be ready to be transplanted. Grafting will be possible a year later.
I personally tested all the above procedures but I had no satisfactory success. To sum up I have reason to believe that the best propagating way is possible using either a sucker or a low young branch directly from the tree: just cut it for a half and cover it with earth to consent a new roots developing, like grapevine.

graftingGrafting :most common grafting way is called "luce's beak". It is generally practiced in the late spring.
As soon as the trunk diameter is large one centimeter the new plant is ready to be grafted. Cut it close by earth in a sloping way . Then select a healthy, vigorous, one year old scion from the sort of plant you want to reproduce; it must present at least two gemmas. Shorten the top and sharp the terminal so to insert it easily between the bark and the wood of the plant you already prepared. Cover the grafting with some mastic. Shorten the leaves. That's all.

Adversities :flysometimes the ambient causes great damages to the plants.
It is already well known that frost and humidity attenuate the olive tree's resistance. But the farmer must fear of parasites too.
The most common diseases are caused by two olive flies: the first one is named Prays oleellus ( tignola ); the second one is named Dacus Oleae ( mosca ). These flies put their eggs into the unripe fruits and in very short time the olives are full of little eggs and worms.
How to get rid of the fly problem? According to the Italian rulement olive trees must be treated once a year (at least) with a "sale di rame / copper salt" solution instead of "solfato di rame / copper sulphate" solution as formerly prescribed. This change was made in 1999 because it was attested that copper sulphate is cancerous ! This treatment must be preventively done every year and it is very efficacious against peacock-eye too.
enulaSince I'm a fervent supporter of organic production I don't use chemicals at all, I let
the nature help me in this matter by the Enula Viscosa; the enula is a perennial bushy plant that grows everywhere, along the roads, in gardens and in fields. Its flowers are yellow and its leaves give off an odor typical of compounds containing protect it from animals or many insects. Now, as it attracts Eupelmus which is the most natural antagonist of olive flay, dissemination of Enula in uncultivated areas of olive trees is essential because it can contribute to pest control in integrated pest management programs.
This defense method is much used in southern Italy.