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Almonds, Brazil nuts, cashews, hazelnuts, macadamia nuts, pecans, pistachios, and walnuts are all tree nuts. Though many consumers lump all nuts into one category, peanuts are not considered tree nuts, as they are a legume, and cashews are actually part of a drupe. While chestnuts are tree nuts, this commodity is covered in a separate Know Your Commodity profile.
Grown on only a small percentage of the nation’s agricultural cropland, the United States still harvests a vast amount of tree nuts each year. Georgia, New Mexico, and Texas dominate in pecan production while California continues to produce the lion’s share of almonds, pistachios, and walnuts. Tree nuts are also among California’s top exports.
Types & Varieties
California is the only U.S. state that grows almonds commercially, and most production is exported across the globe. There are several varieties of almonds including Mission, Nonpareil, Price, Butte, and Padre.
As the nut forms on the tree, it is enclosed in a sturdy hull and inner hard shell. Although almonds are sometimes sold in-shell, they are more often shelled during processing. The product may be further processed through blanching, dry roasting, chopping, or converted into a paste called marzipan (a confection made from honey, sugar, and almond meal).
Brazil nuts grow on the Bertholletia excelsa tree native to the South American Amazon forest. Growing up to 160 feet high with a trunk diameter of 3 to 6 feet wide, the Brazil nut is the largest tree in the Amazon forest. Most Brazil nuts are produced in Bolivia, followed by Peru and Brazil.
Generally eaten raw, Brazil nuts are a good source of protein, magnesium, and Vitamin E, and rich in selenium, a powerful antioxidant. However, people who regularly eat too many Brazil nuts can suffer from selenium poisoning. For this reason, it is recommended consumers eat just a few nuts per day.
Cashews (anacardium occidentale) are the fruit of tropical evergreen trees. The curve-shaped “nut” sprouts from the plant’s drupe, referred to as the cashew apple.
Native to Brazil, cashews were originally exported by Portuguese missionaries to East Africa and India during the sixteenth century. Today, India and Vietnam lead the world in cashew production.
Although the cashew apple is used in beverages, jams, and jellies, the seed is the most consumed element of the plant, often eaten on its own or processed into cashew butter.
Like all tree nuts, cashews are nutrient dense foods with ample protein but also fat. Because cashews are in the same family as poison ivy, the raw nut shells and the resin they excrete can cause dermatitis.
Also called filberts, hazelnuts originated from the Black Sea and Mediterranean regions in Turkey, Italy, and Spain. This area is still the center of production, with Turkey producing more than half of the world’s hazelnuts. The United States ranks third in production after Turkey and Italy.
Although a small portion of hazelnuts are grown in Washington State, Oregon is responsible for nearly all U.S. production. The only tree nut produced commercially in Oregon, hazelnuts are an important crop and frequently featured in confections such as chocolate truffles, cookies, pralines, and chocolate hazelnut spreads.
A popular part of the snack food industry, hazelnuts are sold whole, diced, ground, unshelled, or as a paste or oil.
Macadamia nuts originated in Australia in the mid-1800s and were later introduced to Hawaii in 1881. Though found in tropical and subtropical countries across the world, the round nuts are only commercially produced in Australia and Hawaii.
Two primary species, Macadamia integrifolia and Macadamia tetraphylla, are both native to Australia. Also known as the “smooth shell” species, the integrifolia is grown in Hawaii and produces a round, small nut with high oil content—a characteristic that makes it better for roasting and salting.
Tetraphylla, the “rough shelled” species, is less tolerant of extreme temperatures but produces a sweeter tasting nut. Considered a gourmet nut, whole macadamias are sold salted in glass jars or used in cookies and candies.
Native to North America, the pecan tree belongs to the same family as English and black walnuts and hickory nuts. The pecan tree, which originated in the Mississippi flood plain, was a prominent food source for Native Americans long before European settlers arrived.
Georgia, New Mexico, and Texas are the top three pecan-producing states, with Georgia leading production. Arizona also grows a small amount.
Pecans rank third in consumption behind almonds and English walnuts, and are a top export. They are sold in-shell or shelled, and grade standards are tied to this designation.
Nuts in the shell are graded by size or kernel color, while shelled nut grades are determined by size in halves or pieces.
It is believed that pistachios originated in the Middle East, where the trees have grown for thousands of years. The green nuts eventually reached Greece, Italy, and Spain, then the United States in the 1880s where they grew in popularity.
California is responsible for the bulk of U.S. production, though Arizona, New Mexico, Texas, and Utah also grow in lesser quantities.
Most are sold in the shell, primarily roasted, salted, and sold as a snack food. Some are also used in ice cream, confections, baked goods, and dressings. A single ounce serving includes 6 grams of protein, 3 grams of fiber, and 286 milligrams of potassium.
The oldest known tree food, walnuts date back to 7000 BC and are believed to have originated in ancient Persia. Although walnut trees were first cultivated in California in the 1700s, commercial production did not begin until 1867 and went on to become the nation’s top walnut-producing state.
There are two major varieties grown in the United States: the English walnut and the black walnut. Often called the American walnut, the black walnut tree is native to North America and grows wild across the central and eastern parts of the country.
California black walnuts have a rich, bold flavor and thick, hard-to-crack shells. Because English walnuts feature a milder taste and thinner shells, the latter variety has much broader appeal. A newer variety, the Livermore, is a unique red walnut introduced to the commercial market by the University of California, Davis in 2012. Demand for this mellow, creamy-tasting walnut continues to climb.
Tree nut cultivation and harvesting greatly depends on the variety and growing region.
Almond trees require mild winters followed by a long, warm growing season. Trees should be planted in moist soil 15 to 20 feet apart, and the orchard floor should be smooth, bare, and firm. Between late February and early March, buds burst into light pink and white blooms.
Because most almond trees are not self-pollinating, growers must bring in bees to complete the process. In March and June, the almond shell hardens and the kernel begins to form. By July, the hulls start to split, allowing the shell to dry. When the hulls open completely, it is time to harvest.
Cashew trees require tropical environments with well-drained sandy or loamy soil. Healthy root systems can withstand drought, but adequate rainfall is needed for optimal development. Trees with yellow to gray-brown apples are more resistant to disease and have higher yields.
Trees do not produce fruit until 3 to 5 years after planting, with full production occurring after 10 years. Harvesting season runs from February to May. Cashews are harvested after the nuts fall from the tree. Drying in the sun for 2 or 3 days reduces moisture levels and prevents spoilage. In hotter climes, nuts should be gathered every day.
Pecan trees grow best on hilltops and thrive in warmer climates, often growing more than 70 feet tall with a trunk diameter of up to 6 feet. Unlike almond trees, pecan trees are wind pollinated. For the first 2 years, pecan trees may require double-digit gallons of water a day depending on the season and conditions.
Once mature, a pecan tree will not be damaged by lack of irrigation, although drought can negatively impact yield and nut quality.
Pistachio trees grow best in an arid semi-desert climate with long, dry, hot summers and cool winters. These trees, which begin bearing fruit in 5 to 7 years, are biennial—offering a heavy crop one year and a lighter crop the next.
When it comes to viability, there does not seem to be a maximum lifespan for pistachio trees as they can live for more than a century. In the western United States, pistachios are generally harvested in September or October once the shells have split.
Walnut trees do not produce nuts until they’re about 10 years old, with most production after the age of 30. Typically, heavy nut crops only occur every 2 out of 5 years.
Walnut trees should be planted with 200 to 300 square feet of space around the base of the tree. Trees grown in the open with large canopies generally produce more nuts than those growing in the forest.
Hazelnut shrubs flourish in areas with cool summers and mild winters. These relatively fast-growing plants expand at a rate of 13 to 24 inches a year and reach a maximum height of 18 feet at maturity.
Hazelnut shrubs do best with ample sunlight: a minimum of 4 hours of direct, unfiltered sunlight every day. Hazelnuts are typically ready for harvesting in September or October.
Macadamias, as subtropical plants, grow best in coastal areas where temperatures range between 50 and 80°F. Mature trees are more resistant to extreme temperatures of up to 100°F. Trees typically begin bearing fruit at 6 to 7 years of age. In Hawaii, macadamias typically drop 8 to 9 months out of the year, generally from July to March. In large-scale operations, mechanical sweepers are used to collect fallen nuts, which are then husked and allowed to air dry or sent to processors.
Brazil nuts grow in lowland subtropical humid regions up to altitudes of 500 meters. These massive trees can live up to 1,000 years. Brazil nut pods are round, hard, coconut-like shells, and each fruit contains 10 to 25 seeds.
Between December and March, the pods start to fall from the trees. Nuts are either allowed to fall naturally or mechanically shaken from trees. If the former, they are collected by castañeros, who crack open pods with a machete, place seeds in sacks, and take them to processing plants in nearby cities.
Pecans are typically harvested in a two-step process. In the fall, a mechanical tree shaker is used to knock about half of the nuts from the tree. Then, after the first hard freeze of winter, when most of the foliage has fallen, the mechanical shaker is used again to remove the remainder of the nuts.
Pistachios are harvested differently. Because these nuts split before harvesting, they should never touch the ground to avoid contamination. Instead, a harvester shakes nuts out of the tree into a catch-frame and receiving bin. Nuts are then sent to processing mills to be hulled and dried.
Pests & Diseases
Navel orangeworm is a major insect pest of California almonds, walnuts, and pistachios. Worms bore holes and feed on nutmeat, causing food safety issues. Black pecan aphids attack foliage, causing premature leaf drop, poor nut quality, and reduced bloom in subsequent seasons.
Codling moths attack and feed on walnuts, damaging the kernel. Leaffooted plant bugs can cause severe damage to almond orchards, leading to malformed nuts, internal damage, and stained shells.
Depending on the variety and location, tree nuts can be vulnerable to numerous diseases, including eastern filbert blight, lethal to hazelnuts; botrytis blossom and shoot blight, which can cause tender shoots in pistachios to wither and die; and bacterial spot, also called bacterial leaf spot or shot hole, which affects almond leaves, twigs, fruit, and flowers. All of the above can cause serious damage if not controlled.
Storage & Packaging
Typically, lower temperatures will result in longer storage: in-shell pecans stored at 70°F can keep for up to 4 months, but can last up to 18 months at 32 to 36°F. When stored at 0°F, storage can extend to 5 or more years. Shelled nuts do not last as long as in-shell nuts due to moisture absorption.
References: Almond Board of California, American Pistachio Growers, California Walnut Board, National Pecan Growers Council, University of California Division of Agriculture & Natural Resources, University of Florida/IFAS Extension, University of Hawaii, USDA.
GRADES & GOOD ARRIVAL
There are many U.S. grades for tree nuts: U.S. Fancy, U.S. Extra No. 1, U.S. No. 1, U.S. No. 1 Pieces, U.S. No. 1 Halves, U.S. No. 1 Halves and Pieces, U.S. Select, U.S. Artificially Opened, U.S. Non-Split, U.S. Commercial Halves, U.S. Commercial Halves and Pieces, U.S. Commercial Pieces, U.S. No. 2, U.S. No. 3, U.S. Commercial, U.S. Select Sheller Run, U.S. Standard Sheller Run.
Quality defects include badly misshapen nuts, insect injury, physical damage, rancid product, foreign material, mold, discoloration, perforated shells, etc.
There are no good arrival guidelines specific to tree nuts (individually or collectively).