How Do Pistachios Grow?

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USDA Hardiness Zones 8-10  - add a zone map

 

The pistachio is a small, bushy deciduous tree that belongs to the cashew family. Although it is considered a culinary nut, the pistachio is not actually a botanical nut. The fruit of the pistachio tree is a drupe or stone fruit, with a hard, beige-colored shell which splits open to reveal an edible seed when the pistachio ripens. Female trees produce nuts and male trees pollinate the female trees.

 

A mature pistachio tree grows 25 to 30 feet tall. It is a hardy desert plant that is highly tolerant of saline soil and grows best in hot, arid conditions, such as those found in the southwestern United States. The deserts of the central valley and southern inland California, where average summer temperatures are around 100 degrees Fahrenheit, account for 98% of pistachio production in the United States.

 

The pistachio tree requires well-draining soil and a great deal of sun to grow, as well as a long winter dormancy period. Without long, hot summer growing conditions, the fruit will not ripen. The highly drought-hardy tree is susceptible to root rot if over-watered, but under the right conditions it is cold-hardy up to 15 degrees Fahrenheit. The pistachio tree requires a 6-week period of winter dormancy for healthy growth, during which average temperatures remain between 15 to 45 degrees Fahrenheit. 

 

Trees are dormant December through February, and begin to bloom in March. Seeds ripen in their shells through the summer, and pistachios are harvested from late August through early October. 

 

The pistachio is a slow-growing tree. It takes approximately 4 to 5 years to begin producing seeds, with good production taking up to 10 years. A mature pistachio tree averages approximately 110 lbs of seeds every two years.

 

Seasonal Growth

 

Health Benefits

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Although pistachios are commonly marketed as salted nuts, unsalted pistachios provide the greatest health benefits. 

 

History

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The pistachio tree is native to central Asia and the Middle East. Archaeological findings suggest that pistachios were cultivated in Turkey as early as 7000 BCE. The modern pistachio was first cultivated in western Asia. It derives its name from the medieval Italian pistachio, which comes from the Latin pistacium, Greek pistákion and pistákē,  believed originally to be Middle Persian.

 

Pliny the Elder cites pistachio seeds as a common food dating back to 6750 BCE. Legend says that the Queen of Sheba, who appears in the Bible, had a taste for pistachios and declared them the food of royalty, forbidding commoners from cultivating pistachios for their own consumption.  The conquests of Alexander the Great brought the pistachio from the Middle East to Greece in the third century BCE. Under the rule of Roman emperor, Tiberius, pistachios were introduced to Italy and Spain during the first century CE.

 

Venetian trade routes eventually spread the pistachio to central Europe, where it was nicknamed the “Latin Penny Nut.”  It did not reach the United States until the mid-19th century, when it was introduced as a garden tree. In the early 20th century, hardier varieties from China arrived in California, but the commercial pistachio industry was not established in the United States until 1929. Today, California accounts for nearly 100% of the pistachio production in the United States, and for nearly a quarter of world production.

 

Propagation

 

Pistachio trees are propagated by budding or grafting onto a suitable rootstock. 

 

Harvest

 

Pistachios typically ripen in late August through early October. With most varieties, the skin (epicarp) will turn from green to yellow and then red before it begins to detach from the nut inside.  When the epicarp is gently squeezed and separates easily from the shell, pistachios are ready to harvest.

 

A manual harvest involves spreading a tarp on the ground and using a long pole to knock the pistachios out of the tree. The epicarp is removed within 24 hours of harvesting, or else it may add a bitter flavor to the nut meat.

 

The epicarp hull may be removed by hand or by abrasive action, such as rubbing the pistachios over a piece of hardware cloth or by placing the nuts in a burlap sack and rolling it around

 

The nuts are then dried in the sun for several days.

 

Storage

 

Pistachios can be stored in an airtight bag in a cool cabinet, the refrigerator, or freezer for up to one year. 

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Fun Facts

 

Iran, the United States, Turkey, Syria, China (FAOSTAT, 2010).

 

Pistachios are eaten raw, salted, or used in a variety of sweet and savory dishes. They replace other varieties of nuts in a number of savory dishes, or ground and blended with olive oil, basil and garlic to make a pistachio pesto.

 

Pistachio ice cream and pistachio cookie dough are examples of pistachios’ dessert capabilities. They can also be ground as an ingredient for spreads or seasonings, or milled into a flour to partially replace all-purpose flour in cakes or pancakes.

 

Kerman (female) and Peters (male) are the two most commonly-cultivated varieties of pistachio in the United States. Kalehghouchi, Golden Hills, Lost Hills,  and Aria are other pistachio varieties.

Grow it Yourself:

 

Because pistachio trees require hot, arid summers with average temperatures around 100 degrees Fahrenheit, as well as long winter dormancy periods with low temperatures of 15 to 45 degrees, growing one requires a very particular climate. In the United States, that climate can only be found in southwestern desert regions.

 

Because rootstock for pistachio trees is not commonly available to home gardeners, most pistachio trees are purchased as grafted trees. 

 

Pistachio trees are dioecious, meaning that the male and female reproductive centers are on different trees. For successful pollination and harvest, both varieties must be present (a higher ratio of female to male trees is usual, as only one male tree is required for pollination via spring winds).

 

If you live in the southwest and want to plant your own trees:

- Choose a location with full sun and well-draining rocky or sandy soil. 

- Dig holes slightly larger than the pots that are deep enough to accommodate the root ball, and twice as wide. Take care not to overcrowd, placing trees 12 to17 feet apart.  

- Place seedlings in holes, with the top of the rootballs flush with the surrounding soil, and lightly tamp down soil with a shovel.

- Allow soil to dry out completely between waterings. If leaves begin to yellow, cut back on watering. Pistachio trees are drought-hardy. Under moist conditions, they are susceptible to root rot. Always avoid overhead irrigation, as wet foliage and bark is prone to disease.

 

Pistachios do not require large amounts of nitrogen-rich fertilizer. A fertilizer containing phosphorus, potassium, and nitrogen may be applied once each spring.

 

Young pistachio trees may require staking for support. As the tree grows, prune branches approximately four feet off the ground, and take care to maintain a single-trunked tree. Cutting back the outermost growth each winter encourages the production of fruiting wood.

 

Recipes

 

To prepare your own salted pistachios, add pistachios to a pot of water that allows 3 inches above the level of the pistachios. Add ½ cup of salt for every four quarts of water. Bring mixture to a boil, then reduce heat and simmer for 15 minutes. Drain pistachios and allow them to dry completely on paper towels before storing.