Grow pistachios

Pistachios like it hot and they like it cold… and we love eating them! JUSTIN RUSSELL explains the quirks of growing this delicious nut

At the end of a hot summer’s day in the garden, is there anything quite as appetising as sitting down to a cold beer and a bowl of pistachio nuts? Not in my book. Something about those sweet and salty green morsels makes them irresistible, to the point that I find it impossible to stop at just a handful. Give me a bowlful, and I’ll happily spend an hour meditatively splitting the shells, reflecting on a day well spent.

Despite the nut’s popularity, most of the pistachios that are sold in Australia are imported from places such as Syria and Iran. It was there, in the high deserts of Western Asia, that the tree originated.

The pistachio belongs to a plant family more colourful than the House of Windsor: the Anacardiaceae family. This group of plants contains members as diverse as mango, cashew, sumac and poison ivy, along with the strictly ornamental (and somewhat weedy) Chinese pistachio (Pistacia chinensis). The edible pistachio (P. vera) is much less commonly grown, the reason being its finicky preference for a certain type of climate.

Common advice is that pistachio trees do well in almond country, but the ideal growing conditions are more extreme: hotter in summer and colder in winter. A chilling requirement of at least 1000 hours below 7°C is required in winter, and upward of 600 hours above 30°C are needed to properly ripen nuts. This rules out coastal, highland and southern areas as potential growing locations.

At this point, though inland gardeners can start to dream of pistachio ice-cream. A broad swathe of the country is well suited to pistachio cultivation, from the Riverina in New South Wales to the Mildura region of Victoria, the Mallee in South Australia and the Wheat Belt region in Western Australia.

The northernmost commercial pistachio grower in Australia is in Tamworth, and the southernmost in the Goulburn Valley. These locations are considered marginal, so if you garden in places such as the northern suburbs of Adelaide, areas east of Margaret River, even Alice Springs, you could have a crack at growing pistachios.

getting started

Among pistachio’s quirks is the fact that it’s dioecious – separate male and female trees are required for pollination. In practical terms, it means that you need to fit two pistachio trees in your backyard in close enough proximity for the wind to transfer pollen. If space is tight, the trees can either be multigrafted or duo-planted into a single hole.

The first method involves grafting male twigs onto a female tree (or vice versa). Ideally, this is done in the nursery before you purchase the tree, but if multigrafted plants are proving elusive, it’s possible to do this yourself. Either chip-budding or T-budding is used commercially, but grafting produces good results when it’s done in early spring. For some general grafting tips, visit abc.net.au/gardening and search with ‘Magnus Opus grafting’.

Duo-planting is as simple as it sounds. Dig a planting hole bigger than usual, then pop both the male and female trees into it, spaced about 15–30cm apart, with each trunk at a slight outward-facing angle.

care & harvesting

Pistachios prefer soil that’s well drained and ideally slightly alkaline, so add lime to raise pH if your soil is acid. Like other desert plants, they can tolerate salt, but they hate being waterlogged. A full-sun position is essential. If it’s the hottest spot in your garden – a location where your other plants struggle – all the better.

Watering isn’t essential once the tree is established, but for the plumpest fruit it’s worth giving them a deep drink, preferably using drip irrigation, once or twice a week in summer. Give your trees a feed with a general-purpose fertiliser in early spring and late autumn, but don’t overdo it.

Australia is free from major pistachio pests and diseases, but common fungal infections, such as anthracnose and alternaria, can affect foliage and fruit in humid conditions. The best remedy is to choose the ideal growing climate, but a preventative spray of copper hydroxide can be applied prior to a forecast wet spell.

Expect your first crop after about five years. Harvest in autumn, when the nuts start to split. The easiest way to collect them is to place bed sheets under the tree and knock them off with a stick. Eat the kernels fresh, or dry the nuts in the shell and store somewhere cool and dry.