Pistachio

Family

Anacardiaceae

Habit

Tree

Height

11 m

Spread

8 m

Growth

medium

Lifespan

300 years

First yield

after 6 years

Hardiness

zone 7–10

Shade tolerance

full sun

Soil

Sand, Silt

Soil moisture

dry – moist

pH

7 – 8.5

Edible: Botanically the pistachio is a drupe, and what is eaten is the oil-rich kernel. It is ripe when the hard shell splits lengthwise of its own accord — that is the harvest signal. Freshly hulled and lightly dried, the kernels can be eaten raw; roasted and salted is the best-known form. In eastern Mediterranean cooking they carry baklava and other pastries, in Italy ice cream, pesto and charcuterie such as mortadella, and they also yield nut butter and pistachio flour. The small-fruited Aegina cultivar counts as particularly nutritious and protein-rich and has carried a protected designation of origin since 1996; the Sicilian pistachios from Bronte are the other mark of quality. Storage matters: damp or damaged kernels mould easily, so keep them dry, cool and airy.

Other uses: Beyond the fruit the uses are limited. The wood is hard and dense but available only in small quantities and used locally for turning or as firewood. Economically more important are the related species as rootstocks: seedlings of the turpentine tree and of Pistacia atlantica are the standard stocks for cultivar growing. One clarification is worth making, because it is often confused: the famous resins of the genus — mastic and the turpentine of Chian mastic — do not come from Pistacia vera but from Pistacia lentiscus and Pistacia terebinthus. The shells arise in large quantities during processing and are used as mulch and fuel.

Site: The pistachio needs the hottest, sunniest spot a garden has — outdoors in Central Europe it only succeeds in wine-growing areas against a south wall, otherwise in a container. The limit is not frost but winter wet: the soil must be extremely free-draining, better still a pot that can be overwintered under cover. Two points decide the crop. It is dioecious, so male and female trees are needed — one pollinator to 8 to 12 fruiting trees commercially, one to three or four in a garden. And it is wind-pollinated: bees contribute nothing, and the plant is not a pollinator resource. No meaningful yield is to be expected before the seventh to tenth year. Care: Water sparingly, keep dry in winter and avoid nitrogen-rich feeding — soft wood overwinters badly. Formative pruning aims at an open, well-lit crown; after that thinning is enough. Like many nut trees it tends to alternate bearing, a heavy year followed by a light one; thinning in the heavy year softens this. Diseases appear mainly with moisture: root rot in waterlogged ground, Verticillium wilt, and panicle and shoot blight caused by Botryosphaeria, which can ruin whole plantings. Harvest comes in September when the shells split; the kernels must then be hulled and dried immediately or moulds take hold. Birds and rodents harvest along with you.

Pistachios are easy to raise from seed: soak fresh, unroasted and untreated kernels overnight and sow warm. That route has two drawbacks, though — seedlings vary in fruit size and quality, and it takes years before a plant reveals whether it is male or female. Commercial growing therefore uses grafting: scion wood is chip-budded or T-budded onto seedling rootstocks in summer. The usual rootstocks are the turpentine tree (Pistacia terebinthus) and Pistacia atlantica; for Central Europe terebinthus is the better choice, being the hardiest and the most tolerant of heavier soils. Seedlings of Pistacia vera itself also work but are more sensitive to soil moisture. Scion wood is best sourced from southern European stock.

For wildlife the pistachio is remarkably insignificant, and that is well documented: the USDA report on the attractiveness of crops to bees lists Pistacia vera as not attractive throughout — no nectar or pollen for honeybees, nothing for bumblebees, nothing for solitary bees — and expressly notes wind pollination; animal pollination is not required for the crop. The zero values for nectar and pollen in the database agree with this. It is therefore useless as a pollinator resource, and anyone planting it does so for the nuts. In its native range it does have ecological function: in the dry mountains of Central Asia it forms open woodland that provides shade, cover and structure, and its kernels feed rodents and birds, which in turn disperse the seed. None of that survives in a Central European container.

Notable: can live 300 years, reaching full yield only around its 20th year; the shell that splits by itself is called "laughing" in Persian; Aegina pistachios have held a protected designation of origin since 1996, the Sicilian ones from Bronte count as top quality; tolerates irrigation at 3,000-4,000ppm salt → a hope for salinised drylands; since the 2020s it has been replacing abandoned vineyards in the Aude;

Central Asia and Iran. The native range of the pistachio is documented for Iran, Afghanistan, Turkmenistan, Uzbekistan, Tajikistan, Kyrgyzstan and Kazakhstan — a continental arid region with hot summers and cold winters. From there it was carried through the Near East into the Mediterranean. The largest growing area today is Turkey with 389,451 hectares, followed by California's San Joaquin Valley with 165,518 hectares and Iran with 125,544 hectares. In Europe it is grown in Greece, above all on Aegina, Salamina and Euboea, in Sicily in the provinces of Catania and Agrigento, in Andalusia, and since the 2020s experimentally in the French Aude, where pistachios are meant to replace vineyards that no longer pay.

The pistachio is a tree of semi-desert and dry mountains. Its habitat is continental: long, very hot and dry summers that ripen the fruit, and cold winters. A range from minus 10 to plus 48 degrees is documented. It grows on free-draining, often stony and calcareous soils and is exceptionally salt-tolerant — irrigation water with 3,000 to 4,000 ppm of soluble salts still gives acceptable results, which makes it interesting for salinised dry regions. What it cannot take is humidity and wet soil: in a damp climate it suffers root rot and fungal attack. Old trees root deeply and can live 300 years. In Central Europe it has no natural habitat.