The pistachio tree grows in a very robust manner and gifts us with fruits known and appreciated since ancient times. The pistachio plant originates from the Middle East, and its cultivation spread across the Mediterranean basin among the Greeks and Romans. Today, Italy produces the world’s best pistachios, specifically the famous green pistachios from Bronte. Sicily is the region where the cultivation of this fruit is most widespread, although it is also found in other southern and central regions. As mentioned, the pistachio tree is very robust, but it requires the right agricultural measures for successful cultivation.
Let’s learn about its characteristics and organic cultivation techniques.
Identifying the Pistachio Tree
The pistachio (Pistacia Vera) is a tree from the botanical family Anacardiaceae. Besides the cultivated species Piastacia Vera in our country, there are two other spontaneous species: Pistacia theribinthus, used as a rootstock, and Pistacia lentiscus, better known as mastic. The pistachio is a dioecious plant, meaning some specimens bear only male flowers, while others bear only female flowers. This characteristic needs careful consideration during planting, similar to considerations for crops like kiwi and hemp. The pistachio tree is very long-lived, often exceeding 300 years. It is vigorous, typically reaching heights of 4-5 meters on average, but it can surpass 8 meters. One difference between female and male specimens is that the former exhibit more vigor with more open and pendulous branches. The bark is light gray in young trees but tends to become dark gray over time. The wood is yellow when young and reddish-brown when old. Its texture is hard and knotty, ideal for crafting fine artisanal works.
The pistachio tree is deciduous, shedding its leaves during winter and the vegetative rest period. Its leaves consist of 3-5 leaflets, glossy green in color, oval-shaped, and with rounded tips. They are covered in a light fuzz when they appear in spring, later becoming smooth.
Flowers, Blossoming, and Fruits
As mentioned, the pistachio is a dioecious species, meaning male plants do not bear fruit, but their pollen serves to fertilize the flowers of female plants for fruit production. Pistachio flowers lack petals and are clustered in axillary inflorescences resembling panicles. Male flowers have bracts and large anthers, while female flowers are very similar to very small fruits. In the pistachio tree, flower production precedes leafing. It occurs progressively starting from April. The flower buds are borne on two-year-old branches. A distinctive feature of pistachio flowering is that male flowers develop first, followed after a few days by the female ones. For this reason, male flowers produce vital pollen for only 2-3 days, while female flowers remain receptive for 4-5 days. Pollination is anemophilous, meaning it occurs through wind action. The fruits are grouped in clusters on the plant and are small elongated oval drupes. These consist of a thin-skinned outer layer in green-reddish color. The shell, a smooth and lignified endocarp, encloses the seed, i.e., the pistachio. The edible part, the seed, comprises two valves, typically green in color, covered by a thin film in shades of reddish-purple or greenish-black.
Varieties, Planting, and Transplanting of Pistachio
In Italy, the most widespread cultivated variety is the Bianca, also known as Napoletana or Nostrale. It is characterized by the bright green color of its seed, highly valued commercially. Other locally popular varieties include Cappuccia, Cerasola, Insolia, Silvana, and Femminella. Among foreign varieties, there are Kern and Red Aleppo. Concerning the male variety, used as a pollinator, the most common is named M10. The most commonly used rootstock is Pistacia theribinthus. If not used as a rootstock for female varieties, it can also function as a pollinator. For a good yield in a family orchard, a single male specimen is sufficient to pollinate 8-10 female plants. It’s crucial to ensure the presence of a male specimen; otherwise, only ornamental and unproductive plants will grow. Another recommendation is to transplant already grafted plants that are at least 1-2 years old. This is because on-site grafting often has low success rates, risking the need for multiple attempts.
The planting distance is 5×5, meaning 5 meters between plants and rows. The best time to transplant a young pistachio tree is from the second half of February to the end of March.
Cultivating the Pistachio Tree
Pistachios are mainly cultivated in southern regions. This is not so much due to winter cold resistance (the dormant plant withstands temperatures as low as -20 °C) but because of the risk of cold snaps. As the flowers are delicate and blossom early, a return of cold weather in April can easily compromise the year’s production. Therefore, if one decides to cultivate pistachios in central or northern regions, they should choose very sunny and sheltered areas. Additionally, protection from sudden frosts requires careful attention.
The pistachio tree is robust and adapts well to all types of agricultural soils, even poor and calcareous ones. However, having deep, organic-rich soil is beneficial. This results in robust and lush growth and increased productivity.
Similar considerations apply to irrigation. The pistachio tree grows well in dry soils with limited water. However, if irrigation is available, especially during critical moments, it enhances production. It’s more of emergency irrigation rather than a continuous irrigation system.
Regarding fertilization, the most crucial application is during planting. Mature manure is used following the classic methods of planting new fruit trees. Subsequent years only require lighter fertilization using home compost or worm humus (available for purchase here).
Pruning the Pistachio Tree
The pistachio tree is grown using an open vase form, with scaffolding at a height of one meter. This setup efficiently accommodates all major agricultural operations. The one-meter scaffolding is achieved by topping the plant at the time of transplantation to stimulate the growth of primary branches. In the subsequent season, towards the end of winter, lateral twigs are pruned, favoring the development of 3-4 buds in the upper part of the stem, thus obtaining the scaffolding. This is regarding formative pruning. For productive pruning, it’s essential to note that the pistachio tree produces on 2-year-old branches. Therefore, at the end of winter, a light thinning of the canopy, removing dead and withered branches, promotes ventilation and good light for vegetation. In pruning operations, consider the tree’s tendency for alternate bearing. In lean years, more decisive interventions are possible, limiting interventions during abundant years.
Biological Pest Defense
Fortunately, the pistachio tree is very robust and doesn’t suffer from particular parasite attacks or other adversities. The use of natural macerates such as horsetail, nettle, and garlic easily prevents the onset of any problems.
The pistachio tree enters production quite late, usually from the 5th to 7th year of age. From the 10th year onwards, it reaches its best productivity, lasting for a long time, around 30-40 years. The full maturation of the fruits occurs progressively from August through September. On average, a plant produces 7-10 kg, but it can reach peaks of up to 30 kg. After harvesting, the removal of the husk is carried out, followed by drying the fruits with the shell in the sun, lasting for 3-4 days. The pistachios in their shells need to be stored in jute sacks, in hygienically suitable, dark, and dry places. Shelled pistachios, however, require roasting for preservation. Pistachios find wide use in our culinary tradition, especially in pastries, for making creams, cakes, and ice creams. You can find a diverse range here.