The popularity of pistachio nuts has seen a continual increase in the United States. Touted as a healthy snack and even having several health benefits, there is plenty to drive the trend. However, one of the biggest downsides to these delicious treats is their price. Driven not only by demand but also due to the time, care, and expense it takes to produce them. This guide on how to grow a pistachio tree will give an insight for backyard growers or anyone considering a commercial enterprise.
What You'll Learn Today
- Can You Grow A Pistachio Tree In The US?
- How To Grow A Pistachio Tree From A Seed?
- How To Plant A Pistachio Tree
- How Do You Tell A Female Pistachio Tree From A Male?
- How Long Does It Take A Pistachio Tree To Grow
Can You Grow A Pistachio Tree In The US?
Pistachio trees are grown commercially in hot, dry places, including California, Arizona, and New Mexico.
California is growing the most significant amount of pistachios in America, producing 99% of the total commercial crop.
For anyone wanting to grow pistachios outside of these three states, it is possible in zones 7 to 9, providing that summer conditions are hot, more than 100°F, and dry. Pistachios don’t like high humidity or prolonged rain.
A cool winter is also necessary to allow the trees to become dormant.
The trees were introduced to the United States by an American botanist called William E. Whitehouse. Mr. Whitehouse traveled to Persia (now called Iran) in 1929, returning in 1930 with approximately 20 pounds of seeds that he had personally selected.
Of all the nuts he planted, Mr. Whitehouse only succeeded in growing one that was useful. The tree this nut came from was unknown to him, as it had been selected from a pile left out to dry by the Agah family, pistachio farmers from Rafsanjan on the central Iranian plateau.
Mr. Whitehouse named the tree “Kerman,” which was a well-known carpet manufacturer close to Rafsanjan. This Kerman variety was improved by budding it onto a more vigorous rootstock.
The real commercial growth of pistachios didn’t begin in California until the 1960s and even later in New Mexico and Arizona.
How To Grow A Pistachio Tree From A Seed?
It’s very unusual to propagate pistachio trees from seed. This is because you don’t know if the resulting tree will be a male or a female. As only female trees produce nuts and all-female trees require a male tree to pollinate them, a minimum of one of each is needed to produce nuts.
If you’d like to grow some pistachio trees from seed, it is possible. You’ll need to find some raw nuts that have been dried but not cooked or salted.
Planting The Seeds
- Start by soaking the seeds for 24 hours.
- Next, wrap them in a moist kitchen towel, place this into a plastic bag or into a bag filled with damp sand, and store them in the refrigerator.
- The seeds need chilling between 33°F and 36°F for six weeks. This is to simulate the dormancy period of winter. This process is called stratification.
- Remove the seeds from the bag and place them in moist sand. Temperatures should be kept between 70°F and 90°F, and the seeds checked daily for signs of sprouting. Spray with water to keep the sand damp.
- Once the nuts have sprouted, transfer them to nursery pots with a mixture of 50% potting soil and 50% perlite. Put one seed in each pot, just below the soil surface. Ensure the root is pointing downwards.
- Water deeply, once every few days. This means adding water until it starts draining from the holes in the bottom of the pot. After a few minutes, the soil should feel slightly moist but not wet if you push your finger into it. Don’t allow the young seedling to dry out, as this may kill it.
Growing On The Pistachio Seedlings
Due to pistachio trees surviving in arid conditions, they establish a very deep root system that allows them to reach the water far underground.
Potted seedlings should only be kept in a pot for a maximum of two years, as the pot will otherwise restrict this root growth.
Once you’re ready to plant the seedling out, ensure you choose a position that is suitable where it can stay permanently. Pistachios are not movable once they have been planted out for more than a few months.
Each day, leave the pot in this position for a little longer, providing weather conditions are favorable until the seedling is fully hardened off, after about two weeks. Now it will be ready to plant.
- Soil – The best soil structure for pistachio trees is a sandy loam. Their roots cannot tolerate being wet for prolonged periods, so clay soils are not suitable.
- Space – Sufficient space must be provided to allow the trees to grow unencumbered to their full size. This can be 20 to 30 feet in spread and height once fully mature.
- Sun and Water – They require full sun to fruit well and deep but infrequent watering, allowing the soil to dry out in between. This establishes a deep root system.
- When to plant – Autumn is the best time to transplant the seedlings during their second growing season. Although they can also be planted in early spring before they start to leaf.
Be very careful when unpotting not to disturb the root ball, as this can be fatal to the tree.
Unfortunately, it isn’t possible to tell the sex of the tree until it is four to ten years old when it starts to flower. Regardless of the sex of the trees you grow, both males and females are attractive with ornamental silver-green leaves.
In this video, you’ll see how to propagate a pistachio tree from a seed:
How To Plant A Pistachio Tree
These trees will tolerate summer drought and a good degree of winter cold without trouble. To keep them looking at their best and to optimize health, growth, and fruiting, they need to be watered during the summer and winter.
Winter watering is necessary to allow the tree to recover from harsh summer conditions and when the tree starts producing nuts to help replenish strength.
Because female trees can cause a lot of nut litter once they mature, it’s best to plant them where this won’t cause any issues.
Make sure you space the trees according to their fully mature size. Twenty feet or more apart is best.
Plan out the positions you will plant your trees in, ensuring they will be far enough apart to prevent overcrowding once they mature. If you have fertile soil, you will need greater distances between trees and less for poorer soils.
The recommended spacing is 20 feet apart to plant 109 trees per acre. But 23 feet may be better if you’re planting for the longer term. Some farmers plant at 12 to 15 feet apart but will thin the trees as they mature.
Ratio of Male to Female
Males trees should be positioned equally among the females to ensure good pollen dispersal. Small orchards often place a male surrounded by seven to nine females.
In large commercial orchards where there are more than 600 trees, it’s common to have only one male to every 21 females.
Ensure you draw a diagram if you will be planting a lot of trees. Remember, when they mature, not only do the trees need space, but the machinery to harvest them and take the nuts away for processing will need room to maneuver and easy access to highways, etc.
Hole sizes for each tree should be dug to 1.5 feet square by 2 feet deep. Don’t forget that if the nursery’s soil ball is still attached, you shouldn’t remove it.
Young trees will also require stakes to protect them from the wind. Place two stakes on the prevailing wind side of the tree, and if you live in a particularly windy location, a third on the other side too. This should maintain the tree in an upright position.
When placing the saplings into the ground, ensure that you cover them to the same depth as when planted in their pot. Compress the added soil gently but firmly around the root system, ensuring there are no gaps or voids, as this can be disastrous to the tree.
Once planted, your young trees will require regular deep watering. Placing a good mulch and some well-rotted compost or manure around the base will be beneficial for retaining moisture. It will also help reduce weeds which will compete for nutrients.
Pistachio trees are a slow-growing species and won’t require excessive feeding. You can discover more about this in our article about how to care for pistachio trees.
How Do You Tell A Female Pistachio Tree From A Male?
It’s pretty hard to tell young male and female pistachio trees apart. This is one reason why commercial growers don’t raise them from seed but use grafting techniques instead.
Grafting on a female bud or scion to rootstock will still ensure a female can be produced. Growing from a pistachio nut is a potluck affair, as you won’t know what you have until the tree is several years old.
Not all is lost if you find you have a male tree. You can graft a female onto it, so it bears fruit.
The sex of mature pistachio trees is easier to tell apart. Males grow taller and fuller than females. You can also see some differences in the flowers they produce.
The flower clusters have 13 stems coming from them. Each of these has between five and nineteen small, greenish-brown flowers, which are very inconspicuous.
In male trees, the flowers grow in tight clusters, while on the females, they are a lot more open, and you can easily see the stem between each of them.
Flowering takes place in spring, and typically, the females will have more leaves visible when they start flowering than the males do.
Only the female trees will produce fruit, which is botanically known as drupes. These fruits are grown in heavy clusters where the flowers were, and the weight of the fruit, especially on young trees, can cause the branches to break if there is a strong wind.
How Long Does It Take A Pistachio Tree To Grow
Growing pistachio trees requires patience. Typically you won’t usually see many pistachios until the tree is about seven to ten years of age. Although there are some earlier fruiting varieties, they are often less hardy.
For your trees to produce their maximum yield, you’ll need to wait until they reach 15 to 20 years of age. Remember that as they mature, they will usually become alternate bearing and only give a significant amount of fruits every other year.
Things that will affect growth rate and nut yield include:
- Cultivar – different types mature at varying rates
- Soil type – trees grow faster in nutrient-rich soil
- Nutrients – Giving your trees the additional nutrients they need
- Sunshine – Insufficient sunshine makes growth and nut production slower
- Water – Too much or too little water will stress the tree and even kill it
- Pruning – Excessive pruning can slow growth and nut production
- Space – Cramped trees won’t produce well
- Exposure – Extreme, heat, cold, wind, or rain all have an effect
A healthy tree in a good location can live for 150 to 300 years.
The most important thing to consider when growing pistachios is climate. They must have a good amount of dry heat in the summer and a cool period to induce dormancy in the winter.
Their deep roots require soil that doesn’t meet with rock or a pan at less than 15 feet.
Only female trees produce fruit, and both sexes are required for pollination, so it’s beneficial to know what you have. This isn’t possible when growing trees from seed, and is why commercial farmers only use grafted trees.
Another benefit of a grafted tree is the ability to use hardier rootstock.
To discover more about growing pistachio trees and a huge variety of other farm and animal topics, take a look at our website.