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"Who plows an olive tree, asks for fruit, who fertilizes it, insists on it, who prunes it, forces the tree to give it to him." Lucius Columela Siglo I
The olive tree consists mainly of two parts, an aerial part, and another root part. Between them, it is important that there is a balance in the growth of the olive tree.
Pruning is necessary both to improve the productivity of the olive tree and to keep the tree in better conditions and thus retard to get older. If there is no balance in our pruning, with respect to the rest of the olive tree, we will see how the olive tree will try to restore that balance.
In this post, we will see four of the important objectives to consider in pruning the olive tree.
1. Maximum exposure to the light of leaves and fruits
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Greater exposure to sunlight of the leaves and fruits, more production of photoassimilates, and therefore, greater growth of shoots and fruits = more production.
Both the olive tree and its wild ancestor, the ‘acebuche’, tend to produce a spherical cup. The sphere is the geometric body with the lowest surface/volume ratio. This is a mechanism for adaptation to the Mediterranean semi-arid climate since it constitutes a way to reduce the exposed leaf surface and with it the perspiration.
However, the spherical shape, being the one with the least surface/volume ratio, is also the one who produces the less, since production is directly related to the illuminated leaf surface.
2. Minimum top density
The concept of top density can be referred to as both an olive tree and the entire plot. With low cup densities, sunlight illuminates all olive shoots equally.
With thick olive trees, there are areas and shoots that receive little lighting and are not very productive, as well as being a reservoir of fungi such as the ‘repilo’.
Therefore, low top densities are important not only for lighting but also because they favor ventilation and thus minimize the virulence of fungal and bacterial diseases.
3. Maximum ratio cup volume / weight of wood.
Care must be taken to maintain the lowest possible weight of wood in the top of our olive trees, without reducing the volume of the top. This is of vital importance in adult olive trees, although it is not so necessary in young olive trees.
Shoots that are inserted into young branches will always be more vigorous and productive than shoots that are born in positions on old branches.
Wood will always be a drag on production. The fewer resources the farm has available, the more exquisite must be the management of the wood in the olive grove.
Adult leaves are the only photosynthetically active structures in the plant that act as a source of nutrients. All other olive structures act as nutrient sinks and compete with each other for these nutrients.
For the production, we are interested that the roots, shoots, and fruits have the maximum possible supply of nutrients, while the live wood does not imply any productive contribution.
4. Tool for regulating the quantity and quality of the harvest
With pruning, we reduce the amount of wood at the top, we improve the aeration and lighting of the shoots, and when very high harvests are foreseen, it is a way to regularize the production by minimizing the harvest.
An olive tree without pruning will curdle many fruits, but as they grow, they will be a sink of nutrients so large, that they will grow little, will have little oil and will leave the olive tree exhausted.
Therefore, it is more interesting to have olive trees with low top densities, so that the fruits, having better lighting and less competition with both the wood and with other shoots and fruits, can be thick, and thus carry a lot of oil, which is what we grow for the olive tree.
A pruned olive tree in spring is able to develop vegetative shoots at the same time as the flowers and fruits, in the year of loading, while if the olive tree is not pruned, in a year of loading, it only has resources to develop the flowers and fruits.
In this last situation, the returning harvest will be very low, since there will be the following year just flower buds.