Friday, 06 February 2015 11:22

How do Pistachios grow?

Pistachios are actually the seeds of stone fruit - not nuts.

  • Latin Name:

    Pistacia vera

  • Growth:

    USDA Hardiness Zones 8-10   Click here to view USDA Plant Hardiness 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 that splits open to reveal an edible seed when the pistachio ripens. Female trees produce the seeds 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 time 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.

     

  • Propagation:

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

  • Harvest:

    Pistachios typically ripen in late August through early October. With most varieties, the skin (epicarp) of the fruit turns 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 pistachio.

    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.

    Commercial growers use mechanical harvesters that clean and sort the pistachios.

    The seeds 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.

     

  • History:

    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.  It is believed to have originated in Persia.

    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.

     

  • Top Producers:

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

     

  • Varieties:

    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.

     

  • Products:

    Pistachios are eaten raw, salted, or used in a variety of sweet and savory dishes. They can replace a variety 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.

     

  • Top Health Benefits:

    Although pistachios are commonly sold salted, unsalted pistachios provide the greatest health benefits.

    With 6 grams of protein per ounce, pistachios contain higher protein levels (but a lower calorie count) than a variety of nuts including hazelnuts, cashews, walnuts, and pecans. They also have the lowest fat content, with only 13 grams per ounce.

    Pistachios contain more potassium and vitamin K than most nuts. One cup also covers up to 20% of the daily recommended value for vitamin B6, and they contain good levels of vitamin E.

    The high fiber content in pistachios (3 grams per one ounce serving) provides a feeling of fullness that can be helpful in weight management. They can also play a role in healthy digestion and the prevention and management of type II diabetes.

    Pistachios are a good source of monounsaturated fatty acids such as oleic acid. Regular pistachio consumption can be effective in reducing LDL (bad cholesterol) and increasing HDL (good cholesterol).

    Because of their high levels of monounsaturated fats, pistachios are a terrific skin moisturizer. Eating pistachios can help eliminate skin dryness. They also make an excellent base oil in massage and aromatherapy.

    Pistachios contain  high amounts of potassium and phosphorus.

    They also contain high levels of the copper, a mineral that aids the body in iron absorption and may be beneficial in combating conditions such as anemia.

    Unsalted pistachios contain zero sodium, making them a great snack choice for people who suffer from hypertension.

    Antioxidants found in pistachios, such as lutein and zeaxanthin, reduce the risk of age-related macular degeneration of the eyes.

     

  • 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  very particular conditions. 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 to 17 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.

     

  • Recipe:

    To prepare your own salted pistachios, add seeds to a pot of water with a 3 inch allowance of water 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.