Nut cultivation requires long-term planning and investment before the first harvest. This process involves plant biology, soil science, and specialized mechanical technology. Understanding the journey of these crops, from planting material selection to final processing, reveals a diverse field of modern farming. The methods used to grow these crops vary widely because the term “nut” is used loosely in commerce to describe several different botanical structures.
Defining the Types of Nut Crops
The agricultural category of “nuts” includes three distinct botanical groups, each with unique growing requirements. True nuts are indehiscent fruits with a hard shell that does not naturally open to release the seed, a group that includes hazelnuts and chestnuts. In contrast, many popular tree nuts like almonds, pecans, and walnuts are botanically classified as drupes, which are fruits with a fleshy exterior and a hard inner shell encasing the seed. This difference means the outer layer, known as the hull, must be removed during the post-harvest stage.
Other commercially important crops are simply edible seeds, such as pistachios and cashews, which develop differently on the tree. The final major group is the ground nut, best exemplified by the peanut, which is a legume whose seed pod matures underground. These differences in physical structure and growth habit dictate the necessary cultivation techniques, from planting depth to harvesting methods.
Establishing the Nut Orchard or Field
Nut tree orchards require years of preparation before a commercial crop can be produced. Most modern orchards do not start with seeds because this leads to unpredictable yields and quality. Instead, growers rely on propagation techniques like grafting, which involves joining a desired variety, called the scion, onto a hardy rootstock. This ensures the resulting tree is a genetic clone of a known, productive cultivar and may also confer resistance to certain soilborne diseases.
Two common grafting techniques are the Whip and Tongue graft and T-budding. Once the young trees are ready, they are planted according to a calculated density to optimize sunlight interception and equipment access. Almond orchards, for example, often use a spacing of 21 to 22 feet between rows and 12 to 16 feet down the row to maximize early yields and facilitate mechanical harvesting. This initial planting phase typically takes three to seven years for most grafted nut trees to begin producing a commercial yield.
Cultivation and Ongoing Care
Maintaining a healthy, high-yielding nut orchard requires year-round, specialized care focusing on tree structure and resource management. Pruning is done to shape the trees, often utilizing a Modified Central Leader system. This technique promotes a strong trunk while limiting height for easier maintenance, ensuring sunlight penetrates the lower branches to maximize the total fruiting area. Growers must also remove non-productive growth like water sprouts and suckers to direct the tree’s energy toward nut production.
Water management is precise, particularly in drought-prone regions where trees like almonds require irrigation. During the period of hull split, growers often employ Regulated Deficit Irrigation (RDI) to intentionally reduce water application by up to 50% for a short time. This calculated water stress helps to synchronize the hull split and reduces the incidence of fungal diseases like hull rot. Soil health is maintained through regular testing and targeted fertilization, with potassium often being a focus nutrient, as it is difficult to incorporate once the trees are established.
Pest and disease management involves a multi-pronged approach. Major pests like the Navel Orangeworm and Peach Twig Borer can damage the maturing nuts, while diseases such as Verticillium Wilt and Phytophthora Crown Rot affect tree health. Sanitation is a primary defense, which includes removing and destroying “mummy” nuts left on the tree after harvest to eliminate overwintering habitat for pests. Planting trees on elevated soil berms can also help prevent crown rot by improving drainage and avoiding standing water around the base of the trunk.
Harvesting and Preparation for Market
The agricultural cycle concludes with the harvest, which is largely mechanized for most commercial tree nuts. For almonds and walnuts, specialized tractor-mounted shakers clamp onto the trunk and vibrate the entire tree, causing the nuts to fall onto the orchard floor. The nuts are then swept into windrows and picked up by a harvester, minimizing the time they spend on the ground to prevent moisture absorption and spoilage.
Post-harvest handling is time-sensitive for achieving shelf stability and quality. The first step involves hulling, which removes the outer fleshy or fibrous covering from the shell, a process done immediately for drupes like almonds and pistachios. Drying is the most important step, as it reduces the nut’s moisture content to a low level necessary to prevent mold growth and rancidity during storage. This is accomplished using heated air dryers or by spreading the nuts in thin layers on the ground for natural curing before they are cleaned, sorted, and graded for distribution.