Pistacia vera Kerman

Pistacia vera 'Kerman' is a female variety of pistachio tree originating from Iran and extensively cultivated in California, as well as in many other countries with favourable climates. This selection is prized for its hardiness and productivity. The tree blooms abundantly in mid-April and produces large clusters laden with round, large fruits that become vibrant when ripe, between late August and September. Beneath this fleshy, aromatic, and highly coloured "skin" lies a large, green, nutritious, and tasty nut, protected by a whitish skin that hardens and opens up when ripe. It is this nut that we consume, either fresh or roasted, salted or unsalted.

The 'Kerman' Pistachio tree only bears female flowers. They need to be pollinated by a male tree, particularly the Pistacia vera 'Peters'. This variety is frost-resistant and less prone to alternate bearing*, but it requires a sufficiently long period of cold to induce flowering.

The wild Pistacia vera is native to Central Asia, particularly Iran and Turkestan. In these mountainous, harsh, arid regions, which are very hot in summer and cold and dry in winter, it survives in the form of sparse and residual forests called wooded steppes. The cultivation of the pistachio tree 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. This tree, emblematic of Mediterranean civilization, along with the almond tree, the olive tree, and the pomegranate tree, is once again being considered. Its low water requirements, as well as its high added 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 that produces nuts. It is also a cousin of Schinus terebinthifolius (the "pink pepper") and S. molle used for garden ornamentation in mild climates. It is a dioecious tree, meaning that there are female plants (such as 'Kerman') and male plants (such as 'Peters'). Its growth is slow, but it can live for several centuries. Seedling plants do not bear fruit until they are 8-10 years old. Grafting allows this period to be shortened 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. 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, of a fairly dark green leaflets, crossed by a slightly winged midrib. Flowering occurs before the appearance of leaves, in spring with dense clusters in males and 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) that are greenish 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 with the female plants. One male plant will pollinate 4 to 7 female plants. The fruit, called a drupe, is composed of a fleshy, resinous-smelling husk that becomes vibrant in late summer. Inside, there is the seed, whose edible kernel, the nut, is protected by a light shell that opens at maturity through a process of dehiscence.

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 climatic requirements that should be remembered before planting it in the garden. Overall, it appreciates the same growing conditions as other Mediterranean fruit trees. The female tree is 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.