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.