If you are looking for a perennial nut tree to produce a tasty, crunchy snack full of healthy vitamins and minerals, you may consider planting a pistachio tree. Pistacia vera, a member of the cashew family, requires very specific growing conditions but can be successfully grown and harvested in some regions of the U.S. These fruit trees can grow up to 30 feet tall, with taproots just as long. Their flowers are not showy and lack petals altogether. But what they lack in looks they make up in tasty nut production.
Pistachio trees grow in arid, hot climates that get plenty of sunshine and the seedlings are best planted from potted nursery specimens in late fall. Pistachios contain several acidic compounds that are toxic to horses, but which are harmless to other pets and humans.
|Common Name||Pistachio tree|
|Botanical Name||Pistacia vera|
|Plant Type||Tree, fruit|
|Mature Size||25–30 ft. tall, 15-30 ft. wide|
|Soil Type||Well-draining, sandy, loamy|
|Soil pH||Neutral, alkaline|
|Flower Color||Green, red|
|Hardiness Zones||7–11 (USDA)|
|Native Area||Central Asia|
|Toxicity||Toxic to horses|
Where Pistachio Trees Can Grow
Pistachio trees require a unique climate where summers are very hot but winters have extended periods where temperatures are between 32 and 45 degrees Fahrenheit. In the U.S., the vast majority of pistachio production occurs in central California and certain portions of Arizona and New Mexico that share similar conditions. Because these trees are wind-pollinated, breezy conditions in the spring and early summer are also essential.
Outside these ideal locations, pistachio trees are very difficult to grow.
Planting a Pistachio Tree
Growing pistachios isn’t an option for everyone because of their specific climate needs. The biggest factor to consider is the temperature, humidity, and rainfall of your area. Pistachio trees require very hot temperatures during the day and don't appreciate high humidity or wet soil. It does best in sandy, well-draining, loamy soil. Infrequent, deep waterings are best. Space multiple trees at least 20 feet apart.
Pistacia vera is a dioecious variety of fruit tree. In simple terms, this means that they are not self-pollinating. A tree will either have male or female flowers, and you'll need one of each if you want to actually produce pistachio nuts, which are the product of female trees. Commercial nurseries will identify male and female trees.
Gusty winds in the spring and summer are crucial for a healthy pistachio harvest. The pollen from the male trees must have enough wind to blow from the male flowers to the female tree’s flowers. To ensure their success, male trees should be planted so that prevailing winds will carry their pollen toward the female trees. Typically, trees planted within 50 feet of each other will be able to pollinate. In fact, one male tree can pollenate up to 10-15 female trees.
The pistachio tree needs full sun (a minimum of eight hours daily) and thrives in hot, arid climates.
Though the pistachio tree will grow in almost any soil type, it does best in light, sandy, loamy soils that are well-draining. Wet, heavy soil is not an option for these trees. Because of their long taproots, it is important that the soil reaches deep into the ground.
The pistachio tree is very drought-tolerant and prefers arid landscapes. However, do not allow this reputation to think it gives you an excuse to deprive your pistachio tree of water. They still require plenty of water to produce an abundant nut harvest.
Your tree will appreciate deep, infrequent waterings, allowing the water to saturate the soil. In the heat of summer, extra water is appreciated. Allow the water to drain before watering again; the pistachio does not do well in soggy soil or standing water. For large orchards, many people use irrigation systems.
Temperature and Humidity
These trees like it hot—at least in the summer. Optimal temperatures for the pistachio tree hover at around 100 degrees Fahrenheit. Despite loving such hot temperatures, it does require some winter cold (between 32 and 45 degrees Fahrenheit) for at least 900 cumulative hours in order to initiate new leaf and bud production. However, pistachio trees can't tolerate frozen ground. This very particular temperature requirement—very hot summers with cool winters—means that pistachio is suitable for a relatively small region of the U.S.
Unlike tropical plants that like hot temperatures and humidity, the pistachio tree does not like too much moisture. It does not do well in humid climates.
Before adding any fertilizer, it is important to know what your soil may lack by having a soil test done. If it is lacking in nitrogen, phosphorous, or potassium, you can tailor the fertilization to fit the nutrient needs of your tree.
It is best to apply the fertilizer in the late winter to early spring to help produce a good harvest.
Pistachio Tree Harvest
It typically takes a tree five to seven years to bear nuts, usually in October. Maximum fruiting may not occur until the tree is 12 to 20 years old.
When pistachio nuts are ready for harvesting, the hulls will turn a beautiful pink-yellow color and the epicarp (the outer husk of the nut) will separate from the inner husk. Once this occurs, simply rap the branches to dislodge the nuts and collect your bounty.
For an easy harvest, try placing a sheet or tarp below the tree before dislodging the nuts. After collection, be sure to remove the epicarps within 24 hours for the best flavor and freshness.
Potting and Repotting Pistachio Trees
These trees can be kept in containers for the first three to five years as potted nursery specimens. After this, they should be planted in the garden to allow the tree to mature. This is crucial because of this species' long taproot, which would be stunted with long-term container growth.
Growing pistachio trees long-term in pot,or as indoor plants, is not practical.
Like other nut-bearing trees, the Pistacia vera is classified as a fruit tree. This makes pruning vital to getting the best nut harvest.
When the tree is young, identify branches to act as the main branches for the growing tree. It is best to choose ones that are spaced evenly around the trunk. Avoid branches that are directly across from each other. After choosing the main branches, trim away all branches below the lowest main branch—this should be 24 to 32 inches above the soil. All other branches should be pruned to approximately 4 to 6 inches in length.
Pruning your pistachio tree mid summer will help encourage the tree to branch and grow thicker. To stimulate ongoing growth, you may want to prune your tree two or three times a year.
Propagating Pistachio Trees
Pistachio trees are normally propagated through budding scion plant tissue onto rootstock from a disease resistant species in the fall. This is a complicated, tricky procedure that is rarely done successfully by amateurs. Pistachio trees are not suitable for propagation by rooting stem cuttings, as the resulting tree will not have the same performance as the parent tree.
How to Grow Pistachio Trees From Seed
While it is possible to grow a pistachio tree from a seed, it is not recommended, as it is impossible to guarantee you will get a nut-producing female tree rather than a male tree. Further, the resulting tree will have the genetic characteristics of the grafted scion plant tissue and will be lacking the disease resistance of the parent tree's rootstock.
If you do want to try it, though, is is quite possible to split the shells of pistachio fruit, extract the seeds and place them in a sealed plastic bag with a damp paper towel, then plant them in small containers filled with potting soil when you see the seeds begin to sprout.
But be aware that you will nurse these seedlings for many years before they approach anything like a mature tree, and even then you will probably not be rewarded with a tree that looks or performs like the parent tree.
Common Pests and Plant Diseases
If your pistachio tree is kept in overly moist conditions (whether through irrigation, spacing or climate), this can lead to a disease called Alternaria Late Blight (Alternaria alternata) where black spores can develop on foliage lesions. Botrytis can also be a problem in wet springs, particularly for male trees.
Verticillium wilt (Verticillium dahliae) can be particularly destructive, even causing the death of the tree. Planting a specimen with resistant rootstock can help ensure you will not face this problem.
Pistachio. Horse DVM.