From Cultivation to Harvesting Pistachios

Pistachio is a perennial fruit-bearing tree that produces delicious, shell-covered pistachios. Pistachio (Pistacia vera), in most cases, is referred to as Aegina pistachio, named after the famous variety cultivated on our island of Aegina. Historically, pistachio cultivation in our country began two centuries ago in Aegina and gradually expanded to other regions. It is noteworthy that when we refer to pistachio cultivation, we are talking about the tree that produces pistachios with shells.

Pistachio cultivation involves various cultivation techniques.

Climate:

Pistachio is a deciduous tree that thrives in a cold, short winter, with few rains and a long, hot summer.

Planting:

Pistachio trees can be planted in various types of soils, preferably in moderately composed, fertile soils rich in calcium carbonate and with good drainage. Planting in highly acidic soils or soils with high salt content should be avoided. The pistachio cultivation process takes about six years to enter full production and is subject to the phenomenon of alternate bearing, where a year of intense production is followed by a year of reduced or even minimal production.

The arrangement of planting positions is at distances of 7×7 or 6×6 meters, taking into account the soil fertility. In soils where trees grow more vigorously, larger spacings are preferred. Thus, planting at 7 meters means about 20 pistachio trees per acre, while planting at 6 meters corresponds to approximately 28 pistachio trees per acre. Regarding the ratio of planting male and female pistachio trees, it is recommended to plant 1 male pistachio tree for every 7 female trees. The planting positions of male pistachio trees are kept mixed in the area, ensuring the dispersion of pollen throughout the field.

Propagation:

Pistachio, as a cultivated tree, exhibits a distinct method of reproduction. It is dioecious, meaning there are male trees bearing male flowers and female trees bearing female flowers. In some cases, the phenomenon of protandry occurs, where male flowers mature before female ones, necessitating artificial pollination for fruit formation. Artificial pollination is done manually, starting with the collection of pollen from male flowers, which can be preserved even in refrigerators. Subsequently, at the appropriate time, the pollen is spread onto female flowers to achieve pollination and fruit formation.

Soil:

Plowing of the field is usually done twice a year, from late October to early April, depending on the rainfall each year.

Irrigation:

Irrigation is a critical cultivation technique since, despite being a drought-tolerant species, pistachio has increased water needs during the fruit-filling period (June-August). However, excessive water can lead to fruit shell closure. For this reason, drip irrigation or the use of micro-sprinklers is recommended. Pistachio is wind-pollinated and requires systematic irrigation.

Fertilization/Spraying:

Pistachio trees require significant amounts of nutrients, especially nitrogen, potassium, and magnesium, for proper growth and fruiting in early spring. Additionally, potassium fertilizer can be added in early summer and at the beginning of the fruit-filling stage. Pistachio trees are fertilized during the winter months, either in January or February, choosing periods with high rainfall.

As an additional measure to enhance production, spraying with foliar boron fertilizer during flowering proves beneficial. Spraying occurs from early December to late May, conducted 1-2 times, reinforcing tree resistance to harmful insects, thus safeguarding consumer health. Fertilization and spraying procedures should be carried out according to the guidelines of the agronomists of the Ministry of Rural Development of the region.

Pruning:

Pistachio trees require light pruning, performed from late December to early March, taking into account the characteristics of each tree. The purpose of this pruning includes maintaining the tree's shape, removing dry branches, and renewing fruit-bearing wood.

Excessive pruning can lead to reduced production and an increase in closed shells. Male trees do not undergo pruning to maintain sufficient height. This way, male trees remain taller than female ones, providing more favorable conditions for easy and effective pollination. Male trees undergo pruning only when their growth is excessive and impedes the development of female trees.

Thinning is also crucial, known as deblossoming, where the farmer removes wild shoots (branches) that hinder the free growth of the tree.

Harvest and Processing:

The quantity of the harvest becomes discernible by late April when the fruit begins to form on the branches. Harvesting commences in August, utilizing the traditional method with wooden sticks-nets and lasts for about a month, taking place once throughout the entire year. It is essential to carry out hulling within a few hours, as the pericarp darkens, affecting the endocarp as well.

The fruit undergoes the drying process, either naturally exposed to the sun for about 4 days or subjected to artificial drying in specialized dryers.