Pistacia vera Peters

Pistacia vera 'Peters' is a male pistachio tree known for efficiently pollinating the 'Kerman' pistachio tree and several other female varieties. The tree is hardy down to -15 °C, heat-resistant (up to 45 °C), vigorous, and it flowers quite young, around the age of 4 years. Its flowering, which lasts for 3 weeks between April and May, mostly escapes frost in its cultivation zone and overlaps with that of various female varieties. A 'Peters' plant will pollinate 5 to 8 female pistachio trees. It should be planted in front of the female pistachio tree, facing the prevailing wind, so the pollen is carried to the female inflorescences. The 'Peters' pistachio tree only bears male flowers and does not produce fruits. It has an upright habit and can reach a height of 5 to 6 m with a spread of 3 m.

The wild Pistacia vera is native to Central Asia, particularly Iran and Turkestan. In these mountainous regions, which are harsh, arid, very hot in summer, and cold and dry in winter, it survives in the form of sparse and residual forests called wooded steppes. Pistachio cultivation dates back approximately 4000 years. It originated in the northern part of present-day Iraq and then spread to all Mediterranean regions under the influence of the Romans. Fallen into disuse, this emblematic fruit tree of Mediterranean civilisation, along with the almond tree, the olive tree, and the pomegranate tree, is once again being looked at. Its low water requirements and its high value attract the attention of agronomists and farmers who see it as a tree of the future in the face of climate change.

The true Pistachio tree belongs to the Anacardiaceae family, just like Pistacia lentiscus (the Mastic tree) and P. terebinthus, the mango tree, and the cashew tree. It is also related to Schinus terebinthifolius (the "pink pepper") and S. molle used in ornamental gardens in mild climates. It is a dioecious tree, meaning that there are female plants (like 'Kerman') and male plants (like 'Peters'). Its growth is slow, but it can live for several centuries. Seedling trees do not bear fruit until the age of 8-10 years. Grafting can shorten this period by about 3 years. The most common rootstocks are UCB1, Pistacia terebinthus, and its hybrid with P. lentiscus called P. (x) saportae.

The pistachio tree can reach a height of 4 to 6 m with a spread of 3 to 5 m depending on the variety. Its habit is slightly weeping in female pistachio trees, but upright in male subjects. Its foliage is deciduous, falling in autumn and reappearing in spring. The leaves are composed of 3 to 5 (7) wide and obtuse, fairly dark green leaflets, crossed by a slightly winged midrib. Flowering takes place before the appearance of the leaves, in spring. It takes the form of dense clusters in males, large slightly loose and trailing clusters in females. Each inflorescence is composed of 200 to 250 tiny flowers in males, but 450 to 500 in females. They are tiny, without petals, with small sepals (5 in females, 3 in males) ranging from green to reddish. Female flowers have a voluminous 3-branched stigma, while male flowers have 5 red stamens. The abundant pollen is carried by the wind. To ensure satisfactory pollination, it is essential to determine the direction of the prevailing wind when planting pistachio trees. It is also necessary to choose a compatible pollinator that will flower in sync with the female plants. One male plant will pollinate 4 to 7 female plants. The fruit, called a drupe, consists of a fleshy shell with a resinous odour, taking on flamboyant tones at the end of summer. Inside, there is the seed, whose edible kernel is protected by a light shell that hardens and opens at maturity.

Pistachios, like walnuts and almonds, are oilseeds or nuts. They are rich in lipids, complex carbohydrates, proteins, vitamins B, K, and E. They also contain manganese, phosphorus, and magnesium.

*Being somewhat delicate to cultivate, the fruit-bearing pistachio tree has clear pedoclimatic requirements that should be remembered before adopting it in the garden. Overall, it appreciates the same growing conditions as other Mediterranean fruit trees. The female tree is somewhat prone to alternate bearing, meaning it may produce every other year or even every third year depending on the varieties. Similarly, it is more or less hardy, early, productive... depending on horticultural selections.