Once exclusively eaten by royalty, the pistachio is a member of the cashew family native to Asia and Asia minor. The pistachio is a perennial tree which often expresses an alternate bearing pattern: yearly variation between a hefty and a somewhat minor harvest. This tree can grow up to 30′ tall and takes a few years to bear heavy crops—sometimes as long as 10–12 years—but will begin to produce nuts around 6 years old. Pistachio nuts form from clustered yellow flowers near the ends of branches out of the woody stem. Adding the pistachio as a staple tree in your landscape would be a great idea and not just for the nuts! During fall it turns a fantastic red. If you do want to harvest from your trees, take note that trees are either male or female and you will need at least one male tree to pollinate the females’ flowers.
Seed: Not recommended. See Helpful Links for more advice on how to grow from seed.
Seed Depth: 1″
Space Between Plants: 6′
Space Between Rows: 10–13′
Germination Soil Temperature: 80°F
Days for Germination: 45
Sow Indoors: 2–3 months before final transplant outdoors.
Sow Outdoors: Not recommended.
Vegetative: Propagation via budding or grafting onto disease resistant hardy rootstocks.
Grows best in an arid semi-desert, with long hot dry summers accompanied by winters that are cool and low in humidity. Pistachio trees do not do well in high elevations or temperatures below 15 degrees; that being said, trees do enjoy a nice cool ‘hibernation’ period during winter below 45°. They will drop their leaves during this time. The vast majority of pistachios grown on American soil are from California’s southern desert region. Over 50% of the world’s pistachio production is done in the Middle East, with Iran as the world’s top producer.
Natural: Full Sun.
Artificial: Not recommended.
Soil: Prefers a deep sandy or loamy type soil. This soil must be well-drained. The tap root of a pistachio tree can grow as long as 30 feet.
Soilless: Deep sand culture may be a plausible alternative to soil growing.
Hydroponics: Anything is possible, but, because of its deep root structure, hydroponic growth of this tree may be difficult.
Water: At peak growing season, around mid-May, a mature pistachio can consume up to 40 gallons of water per day and even more during harvest. Proper implementation of a drip irrigation system is recommended.
Nutrients: Nitrogen and potassium should be added to soil regularly. Development of a fertilization program is recommended while keeping in mind your soil type and watching the effects of fertilizers via leaf analysis. Add additional boron and zinc early on in the season to avoid deficiencies later. It also may be necessary to add magnesium and copper mid-season for alkaline soils. Healthy tree growth is recognized by a reddish tip at sites of new branching.
Foliar: Boron, zinc, and copper can all be applied via a foliar spray to resolve deficiency issues.
Pruning: Integral to getting the most of your pistachio tree, decide which 3–5 branches of the young tree will serve as your primary scaffolding in April of the first growing season. Cut all branches that begin at a height of under two feet. Remove any branches that will shade the trunk too much, and trim down all branches that are not part of the primary structure to about half a foot long. A few months later, in mid-summer, trim all of the primary scaffolding branches to about 3 feet long to promote branching out. Maintain an open center structure where plenty of light can reach the main trunk. Weed regularly and remove unwanted nutrient-leeching plants, such as covering grasses.
Mulching: Mulching can retain soil moisture and prevent excessive weed growth.
Pest(s): The pistachio does not have many pests but watch for:
Disease(s): Disease resistant root stocks are available. Trees may still be susceptible to:
Deficiency(s): Boron deficiency will alter flowering patterns and pollen viability, giving lower yield and possibly nut production problems. Zinc deficiency is marked by low leaf concentration.
Rotation: Pistachios can live to be as old as 80! So, leave the rotation up to your grand-kids.
Companions: The pistachio is dioecious, meaning the male and female parts are on separate plants, so in order to fruit, pistachios need more than one pistachio partner. Typically the male to female ratio is about 1:20. Lucky guy.
Harvest: In late August to early October, when the hull of the nut changes from green to a yellowish-red color. A simple shaking of the tree should bring down many mature nuts.
Storage: To prevent mold growth, remove the hull and dry the pistachio nuts within the first 24 hours. The drying process takes about 3–4 days outdoors or about 12 hours in an household oven at around 140°F. After this step is complete, freeze the nuts to kill off any existing larvae or insect eggs that may be present. Store nuts in a cool dark place in a plastic bag or air tight container. Generally nuts keep best at low temperatures, so for storage exceeding 1 year, refrigeration or freezing may be necessary.
Pollinators: Pistachios depend largely on wind for pollination in early to mid April.
Cultivars: There are several cultivars of pistachio on the market:
Fun Fact: Most commercial varieties of edible pistachio are grafted onto the roots of the Chinese Pistache (Pistacia chinensis), a cousin to the pistachio that can thrive in colder climates.
Preserve: Pistachios can be ground into a delicious butter that can be preserved in the refrigerator for up to a year (see Culinary section for a recipe). You can also mix pistachios into a jam recipe with your favorite fruit or sweet root veggie.
Prepare: For best results, eat fresh. Salt before roasting if preferred.
Nutritional: The pistachio nut is a great source of protein while remaining low in cholesterol. The fats that we get from nuts and avocados are the good kind of fats that promote healthy brain function. It is also high in calcium, potassium, and vitamin B-6.
Medicinal: Plants in the family Anacardiaceae are often associated with benefits to the heart. Scientific studies have shown that adding a few ounces of pistachios to your diet will relax the arteries and reduce the workload of the heart.
Warnings: These delicious nut can cause an allergic reaction in some individuals! Consult with a medical professional before consuming, particularly if you have known tree nut allergies.