Pistachio (Pistacia vera)

How well established is this crop?

Initial trial plantings of these crops may have been done. There is little information on plant suitability to the region and no current information on markets, commercial returns or current research. This is a new crop.

Background

Pistachio (Pistacia vera) nuts have been grown as a crop for centuries. They probably originated in the area bordering Iran, Turkistan and Afghanistan. The major producer of pistachio nuts are Iran, Turkey and California with smaller production coming from Australia, India, Pakistan, Afghanistan, Syria, Greece and Italy.

Orchard cultivation in America and Australia has a short history. Of 20,000/ha planted in California, about 90% have been planted since 1970. Australian interest also began in the 1970’s and they have made good progress especially on selecting cultivars suitable for Australian conditions.

The pistachio is a small tree similar to the fig in its straggly growth and large deciduous leaves. Its natural habit is to branch at ground level and it is rare for a trunk to develop unless trained to do so. The roots develop a long taproot making pistachios highly drought resistant. Kernels can be eaten raw or roasted. If grown commercially, the nuts are roasted in the shell and then plunged into brine while still hot. Nuts are then reheated for drying which leaves them preserved in their shell.


Climate

Summers need to have 7 months growing period, frost free for 200 days, with hot and dry weather into the autumn, (similar to the olive). A daily maximum around 30°C is ideal. A short cold period is needed in winter to break dormancy.

Winter Chilling and Frosts

The flowering period ideally should be frost free. This is likely to be mid to late October in Central Otago. Individual flowers open for 5 days and the trees bloom for 10-15 days. The lowest temperature during fruit set should be -3°C or fruitlets will abort.

Rainfall and Irrigation

Pistachios grow best in dry climates. However, irrigation may be required to maintain soil moisture at acceptable levels. They are considered drought tolerant because of their long tap-root.

Wind

Even though pistachios grow into large trees, they still benefit from some wind protection, especially when they are young. It reduces the chance of bruising on the fruit and reduces the drying effects of wind over the summer period.

Soil

Pistachios will not tolerate wet feet for a prolonged period. Ideally soils should be deep, friable, well drained but have moisture retention. They are capable of surviving in poor, stony, calcareous, alkaline or slightly acid conditions. This makes them valuable trees for reclamation and conservation projects.

Fertility

Although they are tolerant of a range of soil pH, a pH between 7.1 – 7.8 is considered ideal. Medium levels of fertility suffice or the tree will produce too much vegetative growth. Pistachios often show Zinc and Boron deficiencies so regular leaf and soil tests will be needed to keep nutrition correct.

Weed Control

Weed control in pistachio blocks tends to be quite straightforward. When young trees are planted, plastic spray-guards are put around the trunks. This prevents rabbit damage and allows herbicides to be sprayed right up to the tree. Weeds growing up inside these guards are removed by hand. As the trees mature the bark on the trunk hardens and herbicides can contact them with no damage to the tree.

Varieties

Pistachios are dioecious meaning male and female trees are needed. As female flowers are receptive for only about 4 days, male trees shedding pollen during the first half of female blooming period should be selected. Usually one male tree is planted to 8 female trees as a 3 x 3 block of females with a single male in the centre. Pollination occurs by wind or air drift, although bees may actually take quantities of pollen and thereby reduce fruit-set.




Pests and Diseases

Verticillium wilt causes branch dieback and may eventually kill the tree. Overseas experince shows Phytophthora parasitica and Armillaria mellea attacking pistachios sited in poorly drained wet sites. It is not known if these diseases are present in New Zealand.

Insect pests are not thought to be a problem with pistachios however leafrollers have been noticed on the foliage of trees.

Layout

A general spacing is 8 x 5m but this may be adjusted to suit your particular needs. Because tree growth is slow, many orchards contain temporary filler trees for the first 10 years. Young trees start cropping from year 4-5, grafted trees 3-4 years, seedlings 7-10 years.

General Management

Tree training to develop a good framework is essential for the first 4 to 5 years. Develop a trunk about 1m high, then train the main permanent branches. Only prune when necessary as resin oozes from any cuts and allows disease into the tree.

Harvest

Unlike most other nuts, pistachios need harvesting prior to falling from the tree. This is because they quickly deteriorate through staining and fungal attacks if left on the ground. Aspergillus flavus and aflatoxin can be a problem wherever pistachio crops are grown.

Commercial crops are harvested with a tree shaker on to collecting sheets. When hand picking, the fruiting branches are picked off avoiding damage to the adjacent fertile buds for next years crop. Smaller crops can be picked by hand.

Equipment

Because most blocks of pistachios will be planted on a reasonable scale, a tractor is required, along with spray units, mowers, forks for transporting bins and maybe a truck to get fruit to a packhouse for further processing.

Moisture content is often 40-50% when harvested, so hulls must be removed mechanically within 24 hours and then rapid drying to between 5-7% moisture is needed for safe storage. Pistachios are served principally as roasted salted nuts, they can also be used in stuffing, cakes, candies, preserved in syrup and are popular in ice-cream.

Returns

Trees usually begin bearing in the 4-5th year after budding, but an economic crop is not achieved until year 7 or 8. In California 8-15 year old trees yield 2 to 8 kgs of inshell nuts per tree giving 200 to 800 kg/ha, 16-30 year old trees yield 8-30 kg/tree (800 to 2400 kg/ha).

Assuming an in shell price of $4.00/kg to the grower, a sizeable area of trees are required for an economically viable orchard. At a higher price of $5.90/kg a 10ha orchard could be viable. Losses of 30% due to no split, empty and stained nuts should be allowed for.



Contacts

The pistachio’s reputation for climatic extremes has encouraged tree croppers in Central Otago and Marlborough to try establishing orchards. The long, hot, dry summers and very cold winters of Central Otago most resemble the climate of the pistachios homelands. Care is required in to select sites with favourable microclimates reducing the risk of spring frosts. The cold tolerant Pistacia terebinthus would appear the most appropiate rootstocks to try.

Further Reading

“Pistachio Production” Leaflet 2279, University of California
“An Introduction to Pistachio Growing in Australia” CSIRO, Australia
“Sample Costs of Establish and Produce Pistachios in the Southern San
Joaquin Valley
References
“Australian Nutgrower” September 1996

Acknowledgement
This artcile reproduced in association with the New Zealand Tree Crops Association.