Pruning olive trees in the shape of a wine glass facilitates the management of olive groves and helps reduce production costs. Therefore, an ever increasing number of farmers are turning to this form of cultivation.
In fact, pruning olive trees using the wine glass technique has at least three advantages: it respects the needs of the tree, helping it express its full productive potential, simplifies pruning, and facilitates harvesting.
Pruning in the shape of a wine glass is suitable for all olive trees (of which there is a huge variety), both those earmarked for oil production and for producing table olives. In addition, it creates the conditions for fairly intensive planting and for the use of mechanical means and facilitators for tilling the soil and harvesting the olives.
Good pruning means less wood and more fruit-bearing branches
Left to its own devices in nature, olive trees would grow as shrubs, what in botany is referred to as a shrubby habitus, nonetheless capable of reaching rather great heights. This tendency of the plant gives rise to the continuous emission of vigorous branches from the roots or from the peduncle of the plant, known as suckers, and robust erect branches on the trunk or branches, known as water sprouts, which compete for the apical dominance of the tops.
The first objective of pruning cuts is therefore to keep the root and aerial parts of the tree in balance, but above all to limit the amount of structural wood in favour of the fruit-bearing branches, which in the olive tree are always those that are one year old.
Two birds with one stone – pursuing the first objective helps achieve the second: facilitate harvesting by concentrating production in the lower-middle part of the tree and in particular in the peripheral portion of the foliage where, for example, it is easier to insert the rakes of the harvesters to detach the olives.
When dealing with relatively small plants (apexes of no more than 4-5 metres in height), operators will also be able to carry out pruning cuts with their feet firmly on the ground, and thus safely, thanks to handy tools, such as shears, loppers and, for larger diameters, chain pruners. All of these tools can be combined with fixed or telescopic extension poles to reach higher branches. Chain pruners are used to remove thicker branches.
The last (but certainly not least in importance) objective of pruning is to preserve the health of the olive tree by encouraging good air circulation and sunlight penetration even in the central part of the foliage to reduce the risk of mould and pest attacks.
Olive tree pruning in the most common forms of cultivation
Various forms of olive cultivation have spread over time. The agricultural traditions of the various countries where the plant is present (the entire Mediterranean basin) have been consolidated based on factors, such as climatic conditions, the peculiarities of the soils with greater or lesser presence of nutrients and water, the botanical knowledge of the time, and the practical needs of farmers.
To give just one example, the repeated topping of the main branches to stimulate the formation of branches in two opposing directions (dichotomous divisions) also had a functional reason: to create a solid, wooden structure to “support” the ladders on which farmers climbed to carry out manual shaking.
The forms of olive cultivation almost all involve a central leader. The main branches (usually 3 to 5) start from the trunk, about 1-1.40 metres above the ground. This is the case with the wine glass, but also with the shape known as globe, which differs from the former in that it has several secondary branches and a dense foliage even within the plant, making it resemble a sphere, as the vegetation itself is used as a natural defence in areas that are highly exposed to sunlight.
Another form of cultivation involving a central leader covered with lateral branches, which are thicker and longer at the base and shorter and thinner towards the top, is what is known as the single leader with free canopy, which is reminiscent of the spindle-shaped form of cultivation usually adopted for other fruit trees. In the monocone shape, on the other hand, the secondary branches are left to grow almost horizontally in relation to the ground.
The free canopy vase is characterised by the fact that the sub-branches are allowed to grow freely, with reduced pruning, and is a shape suitable for mechanised harvesting with shakers acting on the trunk, but requires large planting beds. There is also the variant known as the low free vase, with a trunk about half a metre high, on which the olives are harvested easily with electric or pneumatic rakes.
Lastly, there is the bushy pot, a shape in which the main branches start directly from the base of the olive tree.
Polyconic vase olive tree pruning: why is it called that?
The polyconic vase form of cultivation owes its name to the vase shape that the tree takes with a trunk about 1-1.20 metres high from the ground and the conical (or pyramid-like) shape in which the main branches are modelled, with a wider base near the trunk and a point at the end. It is called polyconic precisely because there are more than one cones (i.e. branches; at least 3-4) and each of them retains the function of a top.
The primary branches are inserted at an angle of about 45 degrees with respect to the trunk, so that the plant is empty on the inside and the foliage grows outwards to a height of 4-5 metres, perfect for harvesting with mechanical facilitators, such as harvesters, equipped with vibrating rakes that are inserted between the fruit-bearing branches to detach the drupes. The inclination can be reduced to around 30-35 degrees in order to have narrower (but also taller) plants when harvesting with mechanical vibrators that anchor themselves to the trunk and/or larger branches to make the olives fall by shaking them.
When polyconic vase olive tree pruning became popular
Until the early decades of the 20th century (but in centuries-old olive groves even until more recent times), the traditional form of olive tree cultivation was the dichotomous vase, also known as the “inverted truncated cone”, since the foliage develops at the top and is sparser near the trunk. However, this involves periodically carrying out what is known as “trimming” of the olive tree’s wood structure to bring the tree back to a lower height and reinvigorate the lower part with foliage. This rather drastic pruning has the consequence of heavily altering the traditional production alternation of the olive tree for at least 2-3 years.
Conversely, polyconic vase training, by reducing the dispersion of the plant’s energies to support unnecessary wood structures, helps to keep production more constant by limiting theproduction alternation between fruitful and scarce years.
The first form of the polyconic vase began to establish itself between 1920 and 1930 and was perfected in contemporary times with the pruning that today also goes by the name of simplified polyconic vase.
Over the last decade, several regional pruning schools have sprung up, offering specific courses on polyconic vase training for olive trees, especially aimed at family olive grove owners.
Polyconic vase olive tree pruning: techniques and pattern
The polyconic vase supports the fructification of the plant during production farming.
Tendentially assurgent branches are formed near the insertion with the trunk. As long as they are small, they should be left on the branch to “suck” sap from the roots. When they start to become too vigorous, instead, they steal light and sap, becoming “water sprouts”. At this point, they should be removed, unless they are needed, by bending them outwards, to replace a branch or part of a branch damaged by the weather, or attacked by disease and pests.
Moving away from the trunk, the first exclusively vegetative branches are followed by secondary predominantly vegetative branches, which should be thinned, but not eliminated completely, as they will replace the productive ones the following year.
In the outermost part of the branch, on the other hand, also bent down by the weight of the foliage, there grow secondary branches which are predominantly productive. There, in short, the olives will grow on one-year-old branches, which one must make sure to preserve from pruning cuts.
Below these secondary branches is the depleted productive zone, also recognisable by the fact that the branches have few leaves, if they have not dried out. These branches must be removed.
In order to limit the vigour of secondary branches and above all to limit the height of the apical tops of the branches, the most suitable intervention to be carried out is the so-called return cut; that is to say, it is necessary to divert the top, by shortening it, onto a smaller assurgent branch among the more vigorous neighbouring ones. After having chosen one branch, you must eliminate all others that might compete with it.
As can be seen, the interventions required by this technique are relatively simple, but require one basic thing: constancy. Only by promptly practising winter and summer pruning (when necessary) will the time to be spent pruning each olive tree be reduced and with it the manpower hours needed both to make the cuts and to remove fewer branches.
Harvesting will also cost less, facilitated by the fact that olive production is concentrated in the lower branches.
Olive pruning and harvesting: Campagnola tools
Equipping yourself with quality tools is important to make clean, precise cuts that the tree will find it less hard to heal. The blades and cutting chains of Campagnola tools are manufactured from the best materials available by applying the most advanced techniques.
The catalogue of products on the market, with the PROFESSIONAL, GREEN and SMART lines, includes hand, electric, pneumatic and engine-driven tools. Many tools share the same power source, which can therefore be used with both pruning and olive harvesting tools.
For more information on Campagnola tools you can consult the online catalogue, watch the video section on new products and the correct maintenance of tools, use the contact section of this website, or contact the official network of local dealers, where you can view and purchase tools, accessories and spare parts.