Pistacia vera L.
AnacardiaceaeCommon Names: Pistachio, Pistache.
Related Species: Mt. Atlas Pistache (Pistacia atlantica), Chinese Pistache (P. chinesis), Terebinth Pistache (P. terebinthus)
Distant Affinity: Cashew (Anacardium occidentale), Mango (Mangifera indica), Ambarella (Spondias cytherea), Yellow Mombin (Spondias mombin), Red Mombin (Spondias purpurea), Imbu (Spondias tuberosa) and others.
Origin: The pistachio tree is native to western Asia and Asia Minor,from Syria to the Caucasus and Afghanistan. Archaeological evidence in Turkey indicate the nuts were being used for food as early as 7,000 B.C. The pistachio was introduced to Italy from Syria early in the first century A.D. Subsequently its cultivation spread to other Mediterranean countries. The tree was first introduced into the United States in 1854 by Charles Mason, who distributed seed for experimental plantings in California, Texas and some southern states. In 1875 a few small pistachio trees, imported from France were planted in Sonoma, Calif. In the early 1900's the U.S. Dept. of Agriculture assembled a collection of Pistacia species and pistachio nut varieties at the Plant Introduction Station in Chico, Calif. Commercial production of pistachio nuts began in the late 1970's and rapidly expanded to a major operation in the San Joaquin Valley. Other major pistachio producing areas are Iran and Turkey and to a lesser extent, Syria, India, Greece, Pakistan and elsewhere.
Adaptation: Pistachios thrive in areas which have winters cool enough to break bud dormancy and hot, long summers. They are drought resistant and very tolerant of high summer temperatures, but cannot tolerate excessive dampness and high humidity. The tree has about the same cold resistance as almonds and olives but flowers later in spring than almonds. Chill requirements are estimated at 600 to 1,500 hours. In this country the pistachio is best adapted to the hot, drier regions of California and the Southwest, especially California's central valley and southern California inland areas. Pistachio trees are not particularly suitable as container plants.
Foliage: The large, grayish leaves have 3 to 5 roundish, 2 to 4 inch-long leaflets.
Flowers: Pistachios are dioecious with male and female flowers on separate trees. Male and female trees must be present for fruit to set, or a branch from a male tree may be grafted on a female tree. The small, brownish green flowers are without petals and borne on axillary racemes or panicles in early summer. Wind carries the pollen from the male to the female flowers.
Fruit: The reddish, wrinkled fruits are borne in heavy clusters somewhat like grapes. Although known as a nut, the fruit of the pistachio is botanically a drupe, the edible portion of which is the seed. The oblong kernel is about 1 inch in length and 1/2 inch in diameter and protected by a thin, ivory-colored, bony shell. Normally the shells split longitudinally along their sutures when mature. Under unfavorable conditions during nut growth, the shells may not split open. The color of the kernel varies from yellowish through shades of green, which extends throughout the kernel. In general the deeper the shade of green, the more the nuts are esteemed. Pistachio nuts are rich in oil, with an average content of about 55%. The trees begin bearing in 5 to 8 years, but full bearing is not attained until the 15th or 20th year. Pistachios tend toward biennial bearing, producing heavy crop one year followed by little or none the next. Production of nuts is also influenced by drought, excessive rain, heat or cold and high winds.
Soil: The trees do best on soils that are deep, friable and well drained but moisture retaining. It can, however, survive in poor, stony, calcareous, highly alkaline or slightly acid, or even saline soils. The root is deeply penetrating.
Irrigation: Pistachios will tolerate considerable drought but do best with deep, infrequent waterings.
Fertilization: Since pistachios grow slowly, they do not require large quantities of nitrogen fertilizer. A spring feeding of a complete fertilizer such as 10-10-10 NPK should be adequate.
Pruning: Pruning can be important to commercial growers in order to shape the trees for mechanical harvesting, but less so for the home orchardist. The trees should be trained to a modified central leader with 4 or 5 main scaffold limbs branching about 4 ft. from the ground. After initial training, little pruning is needed except to remove interfering branches. Heavy pruning reduces yield.
Propagation: The pistachio is usually propagated in California by budding or grafting selected scions onto seedling stocks of P. atlantica, P. terebinthus and P. integerrima. These rootstock species are used because of their vigor and resistance to nematodes and soil borne fungi.
Pests and Diseases: A number of fungi attack the pistachio. The most serious fungal disease in California is Verticillium wilt, which can quickly kill trees of varying age. Most pistachios are now grafted to Verticillium resistant P. integerrima rootstock. The trees are also sensitive to the oak root fungus, Armillaria mellea. Insect pests include the aphid, Anapleura lentisci and several species of leaf-footed bugs and stink bugs. The nuts are also very attractive to squirrels and some birds, including bluejays and woodpeckers.
Harvest: The nuts are harvested when the husk or hull covering the shell becomes fairly loose. A single shaking will bring down the bulk of the matured nuts, which can be caught on a tarp or canvas. A fully mature tree may produce as much as 50 pounds of dry, hulled nuts. The hulls should be removed soon after to prevent staining of the shells. To enhance splitting, the hulled nuts may then be dipped into water to moisten the shell and spread out in the sun to dry. One method of salting the split nuts is to boil them in a salt solution for a few minutes, then redry and store them. Stored in plastic bags pistachios will last for at least 4 to 6 weeks in the refrigerator. Frozen they will last for months.
The pistachio is unique in the nut trade due to its semi-split shell which enables the processor to roast and salt the kernel without removing the shell, and which at the same time serves as a convenient form of packaging. About 90% of California pistachios are consumed as in-shell snacks. Shelled pistachios are utilized commercially in confectionery, ice cream, candies, sausages, bakery goods and flavoring for puddings. They can also be added to dressings, casseroles and other dishes.
Commercial Potential: Pistachio nuts are considered one of the prime edible nuts, along with almonds, macadamias and cashews. The production of pistachio nuts in California has increased dramatically in recent years, from some 4-1/2 million pounds in 1977 to over 80 million today. With additional promotion, production is estimated to ultimately exceed 129 million pounds.
The Pistachio Tree
The scientific name for the pistachio is Pistacia vera L. It is a member of the family Anacardiaceae which contains such widely known plants as the cashew, mango and poison oak.
It is a deciduous tree, requiring approximately 1,000 hours of temperature at or below 45° F. in order to grow normally after its winter dormancy. Pistachio nut trees, generally, are suited for areas where summers are long, hot and dry, and the winters are moderately cold. A native desert tree, it does not tolerate high humidity in the growing season.
The trees are dormant from December through February and begin to bloom with the arrival of warmer weather in late March. The male pollinates the female via the April winds, and the shell of the nut is fully developed by mid-May. Before June ends, the seed inside the shell has begun its rapid expansion and by the first of August, the seed has filled the shell. The nuts, splitting at the seams, are usually ready to be harvested beginning September 10th.
Pistacia vera L. probably originated in Central Asia where large stands of wild trees are found in areas known today as Iran, Turkey and Afghanistan. The first commercial plantings in these countries were most likely started from seeds collected from the best wild trees. The tree was introduced into Mediterranean Europe at about the beginning of the Christian era. The climate in the Tularosa Basin is almost identical to the pistachio producing areas of Iran and Turkey. The altitude of both areas is identical.
Although the pistachio was first introduced into California by the US Department of Agriculture about 1904, very little interest was generated until the 1950’s. Since that time, pistachios have become a significant farm commodity in California.
Plantings have also been made in Arizona, New Mexico and Texas in those areas that meet the climate criteria. The tree flourishes and bears well in well-drained soils, but its root system will not tolerate prolonged wet conditions. It seems more tolerant to alkaline and saline conditions than most other commercial trees. The vigor and productive life of the tree is extremely long lasting. In the mid-East, there are trees on record of having productivity of several hundred years.
The pistachio is a small tree, reaching about 30 feet of height at full maturity. Usual commercial plantings are approximately 120 trees per acre. They begin to produce nuts in the 4th or 5th year after planting, and good production takes 8 to 10 years, with full bearing maturity occurring after 15 to 20 years. Average yield per tree is 1/2 lb the 5th year, increasing to up to 80 lb at maturity.
A large percentage of pistachios is marketed in the shell for eating-out-of-the-hand snack food. Pistachios are a rich source of essential nutrients, fiber and protein. Low in saturated fat and cholesterol free, increasing numbers of people are discovering how enjoyable this delicious nut can be.
Planting, Growing, and Caring For Pistachio Trees
Planting & Growing
Pistachio nut trees are suited for areas where summers are long, hot, and dry, and the winters are moderately cold. It is a small, slow growing tree, reaching about 30 feet of height at full maturity. Pistachio trees flourish and bear well in well-drained soils. They begin to produce nuts in the 4th or 5th year after planting, and good production takes 8 to 10 years, with full bearing maturity occurring at 15 to 20 years. Average yield per tree is ½ pound the 5th year, increasing to up to 80 pounds at maturity.
The trees are deciduous, being dormant from December through February and begin to bloom with the arrival of warmer weather in late March. The male pollinates the female via the April winds, and the shell of the nut is fully developed by mid-May. Before June ends, the seed inside the shell has begun its rapid expansion and by the first of August, the seed has filled the shell. The nuts, splitting at the seams, are usually ready to be harvested around Labor Day. One male tree will provide enough pollen for up to nine female trees.
Dig a hole a little larger than the dirt in the pot. The level of the dirt in the pot should be ground level after planting. Remove the bottom of the pot by tearing or cutting it away from the sides of the pot. Check to see if there are any long roots curled at the bottom. If there are, cut those off even with the dirt. This "root pruning" will actually stimulate more roots to form. Make a cut up the side of the pot, but do not remove it yet. Set the potted plant in the hole and fill in the hole loosely with dirt. Now remove the pot by gently pulling it up. "Heel in" or tamp the loose dirt around the tree. Water in well. Do not put fertilizer in the hole during the planting procedure, but do fertilize with a tree fertilizer containing nitrogen, phosphorus, and potassium each spring, following manufacturer’s instructions.
Keep the tree in good moisture content April through mid-September. Do not water October or November to aid the tree in going dormant. After the tree is dormant, a monthly watering during the winter months will
Pistachios ripen in the month of September almost exclusively around the world with the exception of Australia which harvests in February. In exceptionally hot summers, harvest may be early (last week of August).
How to tell when the pistachios are ripe
The hull of the pistachio is called the epicarp. It is about 1/16 of an inch thick and adheres tightly to the hard inner shell until the nut is ripe. Take your thumb and forefinger and squeeze the nut. If the epicarp has separated from the hard inner shell, the epicarp will easily come apart and can be peeled off.
Besides the epicarp coming off easily, the color also changes. The epicarp has a reddish/yellow color during development. The color lightens in August and when ripe, it is a rosy, light yellow.
Try to time harvest when most of the nuts are ripe.
How to harvest
The pistachios will fall off the tree when the branches are given a sharp shake. A rubber mallet hitting a branch, a fist or mechanical shaker can be used. Put sheets or tarps under the tree to catch the nuts. You don’t want to nuts to fall in the dirt (you will lose them or the epicarp will tear).
How to process
The epicarp should be removed within 24 hours after the nut comes off the tree. If left on longer, it will start to stain the hard, inner shell and will also add a bitter flavor to the nutmeat. If you cannot find the time to remove the epicarp within 24 hours, you can stretch the time needed by keeping the unhulled nuts under refrigeration.
The hull can be peeled off by hand or can be removed by abrasive action. Small growers commonly use an old commercial potato peeler than can rub the epicarp off. Some growers put the nuts in a sack and roll it around with their feet . . . dump the nuts and loose epicarp out on a table and sort the nuts from the hulls.
After removing the epicarp, the nuts should be washed quickly in cold, clean water. Remove the nuts from the water and dry.
A drying table can easily be made. Make a box using 1 x 6’s for the sides, and screen for the bottom. A lid can be made with 1 x 2’s for the sides and clear plastic for the top. The box can be set on saw horses (it needs to be up so the air can circulate). The nuts can be put 3" to 4" deep in the box, stirring them in the morning and evening. Usually, they dry in 3 to 4 days this way and the flavor is delicious. A 4 x 8 drying box will hold about 300 pounds of pistachios.
How to salt
Should you desire to salt the nuts, make a super saturated solution of salt and water (stir in salt until the water is so full of dissolved salt, it will no longer absorb any more and the salt you add doesn’t go into the solution). Dip the nuts in the solution. Remove and return to the drying table or put in oven to roast. Use a low oven (225° F) for 15 to 20 minutes.
How to store
Pistachios keep very well if just a few precautions are taken. In general, the lower the temperature, the longer the storage life of the nuts. Pistachios can be held at temperatures up to 68° F without significant quality deterioration for as long as one year. Prolonged heat turns the oil in any nut rancid. A cool cabinet, the refrigerator or freezer are all good storage locations.
2 cups Heart of the Desert shelled pistachios chopped
1 egg beaten with 2 ounces milk
4 6-ounce boneless, skinless chicken breasts
1/2 cup flour
Dredge 1 side of chicken in flour; shake off excess. Dip in egg wash. Press into pistachio nuts. Sauté in butter for 2 minutes nut side down. Turn and cook for 3 or 4 minutes or until done.
|Creamy Pistachio Soup
4 slices bacon, cut into 1/4-inch pieces
1 small onion, minced
1 bay leaf
6 cups chicken stock
1 tablespoon olive oil
1 cup heavy cream
1/4 cup parsley, minced (garnish)
1/2 cup celery, leaves included
1 garlic clove, minced
3/4 cup dry sherry
1/4 cup rice
3/4 cup shelled Heart of the Desert Pistachios
Salt and pepper, to taste
Sauté bacon in a large saucepan over medium high heat until crisp. Remove the pieces and drain. Add the celery, onion, and garlic to the pan, reduce heat, and sauté until the onion is translucent - about 5 minutes. Spoon the vegetables onto paper towels and blot away the bacon grease.
Wipe out the saucepan, then return the vegetables to it, along with the bacon, bay leaf, and sherry. Bring to a simmer and allow to reduce until all the sherry has evaporated. Stir in the chicken stock and the rice. Bring to a boil, then reduce heat and simmer for about 30 minutes, when the rice is very soft.
Meanwhile, heat the oil in a small skillet, add the pistachios, and toss until they are lightly browned - perhaps 2 or so minutes. Drain on paper towels.
When the rice is soft, discard the bay leaf and puree the pistachios and soup in a blender, solids first. When smooth, return to saucepan. Stir in the cream and reheat. Season to taste.
When ready to serve, ladle into bowls and garnish with minced parsley.
| Pistachio Brittle
2 cups sugar
1 cup light corn syrup
1/2 cup water
1 cup butter
2-1/4 cups Heart of the Desert shelled pistachios
1 teaspoon baking soda
In a 3-quart saucepan combine sugar, corn syrup, and water. Cook over low heat, stirring occasionally, until mixture comes to a full boil. Add butter and continue cooking, stirring occasionally, until candy thermometer inserted in mixture reaches 280°F. Stir in pistachios. Continue cooking, stirring constantly, until candy thermometer reaches 300°F.
Remove from heat. Stir in baking soda. Pour candy onto 2 buttered cookie sheets and spread about 1/4 inch thick. Cool completely and break into pieces.
Makes about 2 pounds.
|Pistachio Ice Cream
2 cups heavy cream, chilled
1 cup whole milk, chilled
1 cup coarsely chopped Heart of the Desert Pistachios nuts
1 cup sugar
1/2 teaspoon vanilla extract
1 drop green food coloring (optional)
Place ingredients in a medium mixing bowl and combine until well blended. Pour into freezer bowl, turn the machine on and let mix until mixture thickens, about 20-25 minutes. If desired, transfer ice cream to an airtight container and place in freezer until firm, about 2 hours. Makes 12 (1/2 cup) servings.