The cashew tree, Anacardium occidentale, is a tropical evergreen species native to the coastal regions of northeastern Brazil. This plant is unique because it yields two distinct marketable components attached to a single structure. The fleshy, pear-shaped body is the cashew apple, which is technically a swollen flower stem or pseudocarp. The true fruit is the kidney-shaped drupe, or nut, which hangs from the bottom of the apple, containing the edible seed.
Establishing the Cashew Tree
Successful cultivation requires a tropical or subtropical environment. Cashew trees thrive in warm conditions, preferring temperatures between 20°C and 35°C, and they cannot tolerate frost. While mature trees are drought-tolerant, they require annual rainfall between 1,000 and 2,000 millimeters.
Cashew trees are adaptable to soil conditions, but drainage is non-negotiable. They perform best in well-drained sandy loam, lateritic, or coastal sandy soils. Waterlogging is detrimental to the roots, and the soil should maintain a slightly acidic pH, ideally between 5.5 and 6.5.
Growers use two primary methods for starting an orchard. Planting seeds is the traditional method, resulting in trees with prominent taproots but also leading to genetic variability. Seedling trees take longer to reach maturity, typically requiring three to five years before they produce fruit.
Commercial growers favor vegetative propagation methods, such as grafting or air-layering, which ensure the new tree is “true-to-type” and preserves the desirable traits of the mother plant. Grafted trees offer a faster path to production, often yielding nuts within 18 months to three years. This accelerated maturity and predictable yield make vegetative methods the standard for commercial plantations.
Ongoing Cultivation and Maintenance
Once established, water management shifts to a cycle that encourages fruit production. Young saplings need regular, deep watering to ensure a robust root system develops, especially during dry spells in the first year. Mature trees are mostly rainfed, but supplemental irrigation can be beneficial during the flowering and fruit development stages, applied roughly every seven to ten days.
The cashew tree’s reproductive cycle requires a defined dry period to trigger flowering. A drought of three to four months is required for the tree to initiate bloom. Irrigating the tree during this time disrupts the natural cycle and inhibits flower and fruit set.
Fertilization should be timed to coincide with growth cycles, typically applied twice yearly after monsoon rains. Young trees benefit from a balanced NPK fertilizer blend to support rapid growth. As the tree matures, the ratio shifts, emphasizing potassium to aid in fruit and nut quality. A general annual recommendation for a mature tree is approximately 600 grams of nitrogen, 200 grams of phosphorus, and 200 grams of potassium, applied around the tree’s drip line.
Pruning is essential for shaping young trees and maintaining mature tree health. Formative pruning involves removing low-lying branches and selecting three to five strong, well-spaced scaffold branches to create an open canopy. Maintenance pruning occurs after harvest, focusing on removing dead, diseased, or crossing branches. This improves air circulation and light penetration, minimizing disease and maximizing flowering for the next season.
Pest management is a concern, with two insect species posing the greatest threat. The Tea Mosquito Bug (Helopeltis antonii) feeds on new shoots, flowers, and young nuts, leading to blighting and potential yield losses up to 100 percent in severe infestations. The Stem and Root Borer (Plocaederus ferrugineus) is destructive, as its larvae tunnel into the trunk and roots, often killing the entire tree. Control involves cultural practices, such as maintaining orchard hygiene and proper tree spacing, combined with targeted chemical applications.
Harvesting the Fruit and Preparing the Nut
Harvest begins when the cashew apple turns a vibrant color, typically yellow or red, and the attached nut reaches full size. For commercial purposes, the best quality nuts are collected directly from the ground after the apple naturally drops. This ensures the nut is fully mature, confirmed by its dense weight and hard shell.
Once collected, the nut must be separated from the fleshy cashew apple. While the apple is highly perishable and often processed into juice or liquor, the nut requires careful processing before consumption. The shell of the raw nut contains a dark, oily, and caustic substance known as Cashew Nut Shell Liquid (CNSL).
CNSL is a potent irritant containing anacardic acid, which is chemically related to the toxin found in poison ivy. Direct contact can cause severe skin burns and blistering. Due to this toxicity, raw cashews are never sold in the shell to consumers, and home processing is inadvisable.
Commercial processing neutralizes this caustic liquid through intense heat, usually by roasting or steaming the raw nuts. The heat treatment volatilizes the toxins and makes the double shell brittle enough to be cracked open safely. Only after this detoxification is complete can the protective shell be removed to reveal the edible cashew kernel inside.