After having been waiting for almost a year – and months of hard work in the field, carrying out pruning operations, preventive phytosanitary treatments, fertilization, tillage and increasingly necessary emergency irrigations – it is time to think about olive harvesting. But when is it the best time to harvest the drupes?
The answer is not unequivocal, because this depends on the ripening characteristics of the different varieties (early or late ones), the quantity of olives per plant, the place of cultivation, the type of expected consumption, the company organization and the year.
In fact, keeping a careful eye on the progress of the season – early spring blooms, summer water stress and early autumn temperature drops – is increasingly important due to the climate changes in the Mediterranean basin, the largest area in the world suitable for olive tree growing. These changes will continue to influence the future development of these plants in Europe, in particular in the progressively hotter Northern territories, in North Africa and in the Middle East with its increasingly arid areas.
So here are ten brief useful tips on how and when olive harvesting.
1) THE OLIVE HARVESTING TIME: THE SCALES OF MATURATION
The fruit of the olive tree is a drupe made up of three parts: the outer skin (epicarp), the middle pulp (mesocarp) and the internal stone (endocarp) which in turn contains the seed (almond).
The state of ripeness of the olive is visually signaled by the enlargement of the fruit but above all by the change in color of the skin (pigmentation process) which progressively passes from the initial green to pale yellow and then to vinous red. When the color becomes dark red-purple, the pulp also ripens. With darker shades tending to black the olives are overripe.
The qualitative harvesting index is expressed with a number between 0 and 5: completely green olives (0); olives turning dark on less than 50% of their surface (1); darkened olives on more than 50% of their surface (2); olives completely darkened on their surface (3); olives partially darkened deep in their pulp (4); olives fully darkened in depth (5).
During maturation, the oil content, the pulp-stone ratio, the consistency of the pulp itself and the resistance to detachment (up to the drop on the ground) also change.
With three types of checks on the state of ripeness, however partially approximate, we therefore try to identify the best time for harvesting also through tools and analyses: a) agronomic/productive ripening; b) technological/qualitative maturation; c) traditional maturation.
2) THE DIFFERENT TYPES OF MATURATION: THE AGRICULTURAL ONE
Normally, in optimal climatic conditions, the pigmentation progress of the olives corresponds to the physiological ripening and there is also the maximum oil yield based on the dry weight of the fruit. However, the accumulation of colored pigments in the skin can also occur for the plant stress due to water shortages and extreme temperatures. Therefore, the agronomic/productive ripening scale considers the hardness of the pulp as well as the color of the olives. Furthermore, the risk of falling from the branches with consequent loss of fruit and/or its qualitative degradation of the same once on the ground is assessed. The verification in the field is carried out with the dynamometer to measure the detachment from the peduncle while with the penetrometer instrument a hole is made in the olives with a one-millimeter diameter tip to measure the degree of softening of the pulp.
3) THE DIFFERENT TYPES OF MATURATION: THE QUALITATIVE ONE
Chemical parameters with analysis carried out in an equipped laboratory are instead the basis of the technological/qualitative maturation scale. The main parameters are the possible acidity and above all the oil yield on dry weight and the phenolic content, since the best harvesting period would be the moment in which the two curves of oil yield and phenolic content are at their maximum.
4) THE DIFFERENT TYPES OF MATURATION: THE TRADITIONAL ONE
The traditional ripening, which can be seen in the field, finally takes place when the olives are completely black and the drupes even a little already withered, since the water content is at a minimum, while the oil yield is maximum.
5) NORTH AND SOUTH: DOES THE OLIVE HARVEST PERIOD CHANGE?
The right moment for olive harvesting varies if the olive grove is located in the countries of the northern part of the Mediterranean (such as Portugal, part of Spain, France, part of Italy) or in the southern one (such as Greece, part of Italy, Tunisia, Morocco, Turkey, Syria), since naturally the length of the olive growing season changes between hotter and colder countries.
Over the centuries, cultivars adapted to the territories have spread, generally more precocious in the North and later in the South.
In general, however, the evolution of temperatures and rainfall in the period between June and November determines the ripening of the olives. Years with hot/dry summers anticipate the times while cool/rainy years delay them.
6) WHEN IS IT EXTRA VIRGIN OIL OLIVE HARVESTING TIME?
For virgin and extra virgin oil olives the harvesting period is from the end of October to the end of November (but sometimes up to January) in the southern territories, while from the end of September to the end of October for the northern areas of the Mediterranean. The beginning of the harvesting operations must also be decided according to the necessary time for the olive grower to end them up.
7) HIGHER QUALITY OR HIGHER QUANTITY?
The goal that the producer wants to achieve also determines the harvest times: higher quality or higher quantity? Usually, in both cases a balance point is sought on a standard level of production. And this is where the difficulty lies and the skill of the grower can be seen.
It is the photosynthesis what supports the formation of oil in the olive, which is largely contained in the pulp (16.5-23.5% of the fresh weight) and a small part in the almond (1-1.5% of the fresh weight).
When it is still in the herbaceous stage (green color) the olive is rich in chlorophyll and its pressing will give a greenish oil, full of antioxidant substances, with a fruity taste and bitter and spicy notes.
With the pigmentation (color from yellow to purplish) the olive reaches maturity, the pulp is very soft and the oil obtained will have a yellowish color and a sweet and delicate flavor without particular aromas. And, most importantly, it will have low free acidity: the parameter that determines the category of oil obtained by mechanical pressing in extra virgin (up to 0.8% oleic acid), virgin (2%) and lampante virgin not for retail sale (over 2%).
In the over-ripening stage of the olive (black color) the oil yield based on dry weight increases again but the oil obtained will also be altered by unpleasant flavors.
8) WHEN IS IT TABLE OLIVE HARVESTING TIME?
For olives to be eaten, the so-called table olives, the harvest period depends on the type of product you want to bring to the table: green olives must be harvested immediately before the start of ripening (from September to October), while the ones turning color when they are pigmented and the black ones when fully ripe.
A treatment by immersion in a liquid – brine with table salt or caustic soda – and subsequent boiling or passage in the oven (for black olives) will remove the bitterness of the pulp (a natural protection against birds) and increase conservation for medium-long periods, preferably in glass jars and in the refrigerator.
Table olives should be chosen with a larger size, pulpy and, even more important, healthy and intact. This means without traces of the olive fly and without abrasions, lesions and bruises.
9) CAN WE HARVEST WET OLIVES?
The arrival of rain in the middle of the harvest period is never good news for olive growers. In the best of cases, in fact, the olive would suddenly swell, it would weigh more, increasing the cost of milling, but it would not increase the final yield in oil, being only swollen with water.
The rain would make the land unusable for several days, delaying the harvest and causing the ripest olives to fall to the ground, thus ruining part of the production.
It would not be a good idea to collect the olives that have fallen spontaneously due to the risk of bruises and molds in contact with the ground. Due to water and mud they would start to rot in a shorter time.
Even harvesting in the rain would be a counterproductive operation: leaves and twigs would also detach from the wet foliage together with the fruit, causing damage to the plant.
10) GET READY FOR HARVESTING AND PRESSING
From September it is necessary to organize the farm for the harvesting operations. Before that time, anyway, it would be important to set up traps against the olive fly. The ground under the plants must then be mowed and the grass residues disposed of to be able to arrange the nets – preferably raised from the ground – which the olives will fall into. The other equipment must also be prepared: mechanical equipment and boxes. The delivery times of the olives must be agreed with the mill, preferably not exceeding 24 hours after harvesting.
CAMPAGNOLA EQUIPMENT FOR HARVESTING AND PRUNING
Campagnola manufactures various mechanical tools for harvesting olives. They can be found within its Professional Line: electric, pneumatic and motorized olive harvesters, depending on the more or less intensive use for which they are intended.
Among the latest products to be launched on the market is the new Alice Star, a high-performance electric olive harvester fitted with flexible, resistant and interchangeable technopolymer teeth, which move between the branches carrying out an opposed elliptical movement, patented by Campagnola, capable of guaranteeing excellent penetrability in the foliage without damaging the branches and the olives.
There is also an engine-driven hook shaker: El Toro Evoluzione K GSM.