How important is the pruning of the olive grove?

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The European olea species includes both cultivated olive trees, as well as wild olive trees or wild olive trees. Practically the only difference between the two subspecies, consists of the amount of resources dedicated to the olive; the rest of vital features are almost identical. Therefore, understanding how wild olive trees live, we will correctly understand the behavior imposed by genetics, in the cultivated olive tree.

The natural behavior of the species, without the intervention of human hands, is based on prioritizing the survival of the individual, so that, once it is guaranteed, resources can be allocated to reproduction.

Juvenile phase

In the juvenile phase of the olive tree, the habit is shrubby, multi-stem, as it is the way it has, on the one hand, to compete efficiently for space and light with herbs and shrubs, while allowing the main growth guides They are more protected from the attack of herbivores, since they mainly browse the external and low branches.

Wild olive tree in its natural environment in southern Spain, without pruning of any kind; browsing of the lower parts is only observed by sheep / goats. If not for browsing, low branches would touch the ground.

Once the shrub stratum is exceeded, olive trees tend to have one or a few trunks, as the low and external branches and trunks dry out naturally by shading the higher central parts and by browsing by herbivores.

Adult phase

The adult wild olive tree is found as a wide tree, of medium height, which can reach up to 15 meters in height, being remarkable for its thick and dense crown.

The high width and density of the crown is the way in which the olive tree prevents light from reaching the ground below and around it, preventing the development of other competing plants, both herbaceous and woody.

In the wild olive tree, olive production does not occur in a significant way until the individual has exceeded the shrub layer, since thus the resources are used to increase the vegetative mass, which will be the one that competes with the rest of the plants in its environment, guaranteeing their survival. Similarly, wild olives are small and have a low pulp / stone ratio.

Wild olive or wild olive entering the adult phase. The lower parts are browsed by goats. It still retains its multi-stem bushy growth, although it has already begun to produce olives. Note how dense the cup is.

The natural form that an olive tree adopts without pruning, locates the leaf and the production exclusively in the external part of the crown, with which the production is low and the quality of the fruit is mediocre. The high crown density of the olive tree naturally also makes harvesting difficult.

Centennial cultivated olive tree not pruned for many years. Its growth habit is practically identical to that of wild olive.

With pruning, it is possible to alter this natural shape of the olive tree to increase its productive performance and make harvesting cheaper.

One-foot intensive olive grove, with inverted conical glass pruning, adapted for harvesting with trunk vibro. The olive trees have been molded to have a single trunk, with the cross at a certain height, with a certain number and angle of branches, as well as a low crown density.

The pruning of the olive tree is very decisive in the final production, being its cost one of the highest of all the management of the crop, only surpassed by the harvest.

This influence on the final production and the high cost of its realization, indicates to us how important it is to acquire both a theoretical basis and a practical skill in the correct performance of pruning to make the olive grove profitable to the maximum.

As we can see, in the cultivated olive tree, the interests of the farmer are very different from those of the wild tree: olive production is the priority, with vegetative growth relegated to the background. The dreaded competition with other plants is eliminated by the hand of man, and with fertilization, nutritional exhaustion is avoided, with the olive tree as its sole mission to produce fruit.

Premises for olive pruning

The pruning of the olive tree is carried out following a series of premises, in a very specific order.

Adapt pruning to harvesting

Pruning must be adapted to the way of harvesting, so that it is fast (economical) and not very harmful to the olive tree. Let us remember that harvesting is one of the most expensive operations in the management of the olive grove.

The crown design obtained with pruning must be closely linked to the harvesting system that is going to be used, so that it will not be the same for a one-foot olive grove, intended for harvesting with a trunk or branch vibrator, than for an olive grove. in hedge, collected by a combine harvester.

Optimize canopy lighting

Pruning should optimize the lighting of the entire canopy. In this way, fruiting occurs throughout the crown, not only on the outside. Well-lit shoots grow and produce more, while poorly lit shoots grow and produce little, while continuing to consume light, water and nutrients, negatively impacting the rest of the tree.

Maximize leaf/wood ratio

Pruning must maximize the leaf / wood ratio of the entire tree, avoiding both dry branches defoliated due to lack of light in the internal and lower parts of the crown, as well as long sections of thick wood without leaves on the branches. main, in fact due to the pruning itself to adapt the height of the olive tree to the harvest.

Poorly lit branches consume more photoassimilates than they produce; thick woods exposed directly to light produce suckers that steal sap from productive branches. The higher the leaf / wood ratio in the olive tree, there will be fewer areas in the crown that consume more than they produce, with better vegetative growth and production.

Therefore, pruning must always achieve the greatest amount of leaf, with the minimum amount of wood possible, since by its own function, the amount of leaf is very directly related to production, and the wood in turn represents a consumption of resources, so their amount in the tree should be minimized.

Adapt olive tree size and shape

Pruning adapts the size and shape of the olive tree to the environment in which it vegetates, to avoid competition for light and water between the olive trees themselves.

In thick frames, the size and density of the olive tree should be low to avoid shading between the trees themselves. In olive groves with little water availability, the crown volume must be reduced to allow the root apparatus to be able to supply the productive shoots with enough raw sap to bear fruit. Specially in the youthful phases of the olive grove, we must not forget the balance that must exist in the leaf / root relationship.

Before going into production, a greater biomass of the aerial part is capable of producing more photoassimilates for a greater root biomass, which in turn is capable of pumping more water and mineral nutrients from the soil to the crown in the form of sap. gross.

Very severe formation pruning actually slows down growth and entry into production.

Light pruning of a seedling of a few months. The seedling is enhanced very gradually, up to the height of the future cross. Let us remember that the natural tendency of the species in the juvenile phase is that of the shrub, so the elimination of the lower branches must be very progressive, so as not to cause the appearance of vigorous suckers in excess throughout the entire length. trunk, and thus paralyze the growth of the upper part of the tree.

FAQ

Let's see what are the most frequent questions regarding pruning:

Time to prune

Winter pruning as such, which makes thick cuts, many of them with the intention of renovation, must be carried out in a period free of strong frosts, between harvesting and sprouting.

For most olive groves in the northern hemisphere, the ideal date is between January and March. In olive groves with mild winters because they are a few meters above sea level or on south-facing slopes, where early harvests are made, pruning can be done even from November.

In olive groves to the north of the distribution zone, in the mountains or in low locations with strong reversal frosts, it should be pruned between March and May. In olive groves exposed to strong frosts, a crown thickness somewhat higher than normal must be maintained.

If due to scheduling problems, winter pruning is delayed to spring, you should avoid cutting thick branches destined for renewal, while leaving a bit more stump in the other cuts, as healing is worse when peel off the bark of the wood in such cuts.

Summer pruning, which would technically be a green pruning, and which is usually called clean, is not widely practiced in most areas, being relegated to the elimination of the branches of the trunk and little else, which is called desvareto.

However, it is very positive for production, quality and collection costs. It is more necessary, against thicker foliage and loaded with olives, we find ourselves in the olive tree in summer. The ideal date would be between July and September, consisting of the elimination of unnecessary suckers from the base, trunk and crosses, favoring the development of those destined for renovations, and also eliminating thin branches that are poorly lit, crossed and parallel with other better ones. located, even if they carry olives.

With the summer pruning, badly lit branches and suckers are eliminated, which produce little or nothing but do carry sap, thus allowing a better development of the fruits of the current harvest, as well as an improvement in the nutrient reserves of face to the next campaign. In addition, the thinning of the glass greatly facilitates the harvest, which we must not forget that it constitutes the highest cost of the olive grove.

Summer pruning, almost exclusively desvareto, in which the suckers on the base and the cross have been removed. If in the winter pruning the crown was cleared enough, in the summer pruning it is hardly necessary to intervene in this area of the olive tree.

Winter pruning prioritizes thick wood cuts, so the main tool would be the chainsaw. Summer pruning prioritizes the elimination of suckers and fine twigs, so it is decided to use hatchet, hocino and manual saw.

It is very important that for the summer pruning, the person who performs it has robust knowledge of pruning, since they can be eliminated by mistake, twigs and twigs destined for future renovations.

Elimination by mistake of varetas destined to the renewal of the branch cut in winter.

Frequency to perform pruning

The frequency of pruning depends mainly on:

• The intensity of the vegetative growth of the farm, which in turn depends on the climate, irrigation and variety.
• Intensity of the last pruning performed.
  
  
  

The more difficult it is to collect the olive tree, the denser and worse it is illuminated, the worse the leaf / wood ratio it has, or the worse the water and light situation the olive tree has, the more pressing will be the pruning.

The most advisable thing would be the biennial pruning, with a moderate intensity that allows to maintain this frequency in time, complemented if necessary with the summer cleaning.

In olive groves with intense vegetative growth, mainly in climates with few months of vegetative stoppage and irrigation, in the end it should be pruned annually and even revising something in summer, depending on the intensity of the winter pruning.

Due to the fact that pruning is of great importance in the olive grove both due to the increase in production and the cost involved in carrying it out, the ideal would be to carry out a detailed analysis each year in each homogeneous plot of the need or not to prune and in case of pruning, define the criteria to follow in pruning that plot.

It is convenient to write in writing the criteria that we are going to use to decide in terms of pruning, in order to have an annual record of them, which can help to relate current situations with previous actions.

There is a disease in which pruning can have some control capacity. We are talking about tuberculosis.

Tuberculosis or wart consists of nodules or tumors that appear on young branches with still smooth bark, preferably of little thickness, which greatly weaken the tree.

Its incidence depends mainly on the variety, also influencing the climate and management.

The new tumors settle in small wounds in the bark of the young branches. These wounds can be produced by hail, by harvesting (especially with combs in olive trees with sap in motion), by frost and by the brush itself of the branches with the wind.

A very sensitive variety would be the cornicabra, the native of Castilla la Mancha.

Apart from foliar treatments with copper, pruning is the only control tool for this disease.

In affected olive trees, winter pruning, if possible, should be done with the olive tree dry, without recent rain or dew. At the same time that thick branches are removed, it is very important to eliminate very affected thinner branches, since they are the source of inoculum that continues to infect the rest of the tree on a recurring basis.

There is practically no benefit in disinfecting pruning tools if you are pruning on a farm where the condition is homogeneous between trees and branches. It would be interesting to do so in case, when going from affected olive trees to healthy olive trees, but in the same way, an olive tree can be healthy from tuberculosis because it is not a sensitive variety or some condition like that.

In olive trees affected by tuberculosis, it is highly recommended to influence the summer pruning a lot, as it is done in dry weather in which there is no spread of warts by pruning. The objective is to re-sanitize very affected shoots, but above all, to leave the olive tree quite clear, so that during the harvest there is no excessive friction or blows on the foliage.

We are going to see several aspects to take into account in each of the different prunings depending on the type of olive grove in question.

Pruning the traditional olive grove with a wide frame and several feet

The pruning to be carried out depends mainly on the method of collection and the variety, also influencing other variables such as climate, soil, irrigation, etc.

For harvesting with a one-person vibrator of branches assisted with rods or combs, the olive tree must have a squat appearance, being limited in height. The highest branches will always be secondary renovations of little thickness, which are gradually renewed as they reach an excessive height and thickness. The main branches must tend to horizontality, and be well provided with horizontal and lower branches. A leafy crown should be avoided, to facilitate hooking and shaking.

Centennial Picual olive tree of 3 feet, adapted to harvest by back vibrator.

In the case of collection by vibration of the trunks, the main branches must have an upright bearing, with few vertical secondary renewals, as well as few horizontal and pendulous branches, as they suffer from vibration or vibrate badly, respectively. The renewal rate of primary branches must be high for this type of collection, looking for olive trees with many young branches inserted directly on the heads.

1 foot wide frame traditional olive grove pruning

For harvesting with a back vibrator, an olive tree must be formed mounted on fairly horizontal main branches, with a variable amount of secondary renewals, depending on the frame, variety, etc. The speed of direct renewal depends on the variety, setting, climate, etc.

Centenial olive tree pruned to harvest with manual back vibrator.

For harvesting by vibration to the trunk, a crown formed by several fairly erect branches is needed, with enough space between them, with few horizontal or pendulous branches. In this case, direct renewal should be the priority, since the most easily harvested and productive tree model in this case is the one with many young branches inserted directly into the cross.

Centenary olive tree of 1 foot, recently pruned for harvesting with vibro.

1 foot intensive olive grove pruning

The traditional olive grove of northern Extremadura has been governed by these parameters for centuries. The planting frames of this olive grove are usually 5 to 8 meters in the streets, and distances between olive trees from about 4 to 8 meters.

The points that will have to be taken into account in this type of pruning will be:

• Adaptation of olive trees to the harvesting system.
  
  
• Regulation of the size of the olive tree so that neither light nor water are limiting.
  
  
• Avoid the decline of the leaf / wood ratio of the olive grove over the years. This is the most important and unknown problem in this type of olive groves.
  
  
• If the harvesting is done with a branch vibrator, carried by the operator on the back, and shaking, either with a stick or combs, the height of the olive trees must be controlled, both that of the hooks and that of the branches to be beaten. . The olive tree must be quite clear of ramón to favor quick couplings and bending. With this harvesting system, the olive tree is capable of being allowed to grow quite wide, being able to keep large crowns if the environment allows it. The olive tree should look relatively squat, shaped like a wide bowl.
  
  
• If harvesting is done with a trunk vibrator, the branches must have a narrow angle with the vertical, and the presence of horizontal and pendulous-low branches must be minimal. The olive tree is allowed to grow a lot in height, as the highest and most vertical branches are stripped of all the olives by their own vibration without the help of shaking, the work of the vareadores being relegated to the more pendulous branches. The olive tree must have an inverted cone aspect, narrow at the bottom and tall and wide at the top. The crown is allowed to grow quite high in height, but little in width.

1 foot olive tree in intensive frame recently pruned, prepared for harvesting with vibro. There are no major horizontal or pendulous branches, the main ones being at a fairly narrow angle to the vertical, which will allow good knockdown efficiencies in harvesting.

Pruning the olive grove in hedge

The olive grove in hedge is the one that is arranged with a width of streets of 3.5 to 6 meters and distances between olive trees from 1 to 2 meters.

The harvesting system for this type of plantation is that of a riding harvesting machine with internal shakers that cover the entire hedge.

• The trees will have a height of about 2.5 meters, a width of around 1 meter, with no productive branches below 0.5 meters above the ground, forming a trellis.
  
  
• Olive trees can have a single axis in their juvenile stage, with a monoconical arrangement, although the most advisable thing is to form a cross between 50 and 100 cm in height, with 2 or 3 vertical main branches and the rest of the crown formed by pendulous twigs.
  
  
• The objective is to keep the hedge flexible and within the limits allowed by the combine, always maintaining a high leaf / wood ratio..

• In the varieties of pendulum bearing such as Arbequina, mechanical pruning, to good results for the lower ones, acceptable for the lateral branches and permissible for the upper parts. Combined with manual pruning, mechanical pruning is a very good option from an economic point of view.

• The lowering or topping pruning is performed mechanically with a bar of rotating and cutting discs at a height between 2.5-2.7 m to avoid shading the sides of the hedge.

• Side pruning is to keep the width of the hedge suitable for the harvesting machine, to remove thick horizontal branches that could be badly damaged by the harvester and to prevent shading of the lower parts.

• It is important to ensure that wood does not accumulate inside the hedge, making a constant and gradual renovation.

• The pruning of lower branches or "skirting" is usually done mechanically with undercutting machines that are attached to the front of the tractor or with manual hedge trimmers at a height between 50-60 cm from the ground. When they are large farms, the mechanical option is used through streets, where in the same pass half of the bottoms of two rows of olive trees are cut.
  
  

The Arbequina variety is very pendulous, so it has a natural tendency to drop the shoots due to the olive's own weight. In turn, the harvesting machines of the super-intensive olive grove cannot harvest the production that is below 0.5 meters in height, so the pruning of the underside is a routine action in this type of plantation.

Super-intensive Arbequina olive tree formed into a palmette with 2 main branches.

Conclusions

Reducing production costs and opting for a productive olive grove are the main reasons why the professionalization of olive grove pruning is becoming a fact and a reality, with training modules in olive grove management being increasingly in demand at ESAO.

Within the management, specifically pruning, it requires face-to-face training, given by qualified personnel who are capable of evaluating the different parameters of each olive grove, in order to face the most appropriate approach for pruning.

It is not about adapting our olive grove to a pruning technique, but about carrying out the pruning that best suits our olive grove, and which may be different in each campaign.

Training in Olive Grove Pruning becomes one of the main axes of the professionalization of the olive sector. At ESAO, the Olive Grove Management Course is being one of the most demanded by all those producers or cooperatives that are committed to an increasingly productive and healthy olive grove.