Olive & Oil 02/01/2012

Is pruning olive trees in June so wrong?

Rediscovering tradition in olive culture is beneficial but sometimes the solutions suggested by old times are not the best one to make the most of our olive trees. The olive tree pruning should be a mix of tradition and innovation

At the very end of the olive season, which in the centre and North of Italy had been very short this year, due to the scarcity of olives, it is quite frequent to see olive trees just pruned or in pruning stage.
The warm days of this season encourage the olive tree growers to prune their trees now in order to reduce the workload in spring.
Which are the risks derived from a so early pruning?

Of course the main issue is to increase the possibility of damages related to cold temperatures. As a matter of fact, given the mild temperature, the olive tree is still in the “sucking” stage, i.e. it is still in the vegetative phase. This condition of incomplete adaptation to winter times is dangerous per se; this is even worst if the tree has recent pruning wounds.

Moreover, as discovered by the Università Politecnica delle Marche e dall'Assam, a heavy early pruning can induce a strong reduction of the fruit number, stimulating in this way the emission of epicormic shoots. This event would then require strong intervention in the next year or even a green pruning (during the summer).

Another interesting result of this research says that a small pruning can be done in June without any negative effect on the maturation and the total fruit quantity. The necessity to perform the pruning before the vegetative stage of the tree then can be considered as an outdated traditional knowledge, whenever the pruning is performed properly. In particular, it is important to avoid that in late May or June the positioning of flowers on the tree influence the pruning strategy. I.e., it is important to operate the pruning rationally, without been influenced by the desire to maximize the quantity of fruits.

Therefore, it is important to remember that the olive tree produces fruits on the one-year-old branches and that it is important to free some space inside the foliage to allow the sprout of new branches that will be productive on the next year.

Hence, if it is worth discarding the traditional knowledge as for banning the pruning in June, at least in the centre of Italy, where the research took place, another traditional procedure, the branch folding, has been rediscovered.
In this case the research was carried on by the University of Perugia on a super intensive olive tree cultivation in Umbria. The procedure consisted in bending and folding the branches toward the interior of the row by taking advantage of the wires of the structure. This practice allowed a strong reduction in the pruned volume (0.6 kg per tree vs. 1.8 Kg per tree for the traditional pruning) with a consequent increment of the fruit volume (4.7 kg per tree vs. 4.2 kg per tree). Hence, the branch folding allows a better vegetative control and an increase in the productivity thanks to a better vegetative/productive equilibrium.

If for the super intensive cultures the wires of the structure can help, avoiding the old practice to hang loads to the rising branches, in normal situations stretching the young branches, i.e. folding the branch manually two or three times almost at the breaking point, can be enough. In this way the branch will loose some strength and will stop rising high. This requires a bit of practice but it is extremely cheap and fast and it is very indicated for the young cultivations, where it is important to keep a thriving vegetative volume to favour the conclusion of the juvenile stage.

di Alberto Grimelli