Cashews are a popular snack, but their journey from flower to edible nut is often a mystery. They grow in a unique way, attached to a fleshy, colorful fruit. This process involves distinct stages, from tree growth to the formation of its unique fruit structure and initial processing.
The Cashew Plant
The cashew tree, scientifically known as Anacardium occidentale, is a tropical evergreen species native to northeastern Brazil. These trees exhibit a low-branching, spreading growth habit, forming a dense canopy. While wild cashew trees can reach heights of up to 14 meters (46 feet), cultivated varieties are often dwarf, growing around 6 meters (20 feet) tall for easier harvesting and increased yield.
Cashew trees thrive in warm, tropical, and subtropical climates, ideally with temperatures between 24-28°C (75-82°F). They are sensitive to frost and require a well-defined dry season, which is crucial for flowering and fruit development. While adaptable to various soil types, cashews grow best in well-drained, sandy loams with a slightly acidic pH between 5.5 and 7.5.
Cultivation and Growth Cycle
Cashew trees can be propagated through seeds, though this method often leads to genetic variation in the offspring. For commercial cultivation, vegetative propagation techniques like grafting or cuttings are often used to ensure desirable traits from a parent plant are maintained. Grafting involves joining a chosen cultivar onto a hardy rootstock, which can lead to earlier maturity and higher yields.
After planting, a cashew tree begins to flower and produce nuts within three to five years. Optimal growth occurs with ample sunlight, ideally receiving at least 6-8 hours of direct sun daily. While mature trees are drought-tolerant, consistent moisture is beneficial during fruit development. The trees accumulate nutrients during the rainy season, preparing for the dry season when flowering and fruiting predominantly occur.
The Cashew Apple and Nut Formation
The development of the cashew fruit is distinctive, beginning with small, star-like flowers that appear in clusters. These flowers are a mix of male and hermaphroditic types, with pollinators like bees playing a role in transferring pollen. Once a hermaphrodite flower is fertilized, the true fruit, which is the kidney-shaped cashew nut, starts to develop.
This “nut” is botanically a single-seeded drupe, encased in a hard, two-layered shell that contains a caustic oil. As the true nut develops, the flower stalk, or pedicel, begins to swell and enlarge. This swollen stalk transforms into the fleshy, pear-shaped structure known as the “cashew apple.”
The cashew apple is considered a pseudofruit or accessory fruit because it does not develop from the flower’s ovary. It ripens into a vibrant yellow or red color, weighing 10-15 times more than the nut itself. The nut remains firmly attached to the bottom of the cashew apple, creating a unique fruit structure. The time from flowering to nut maturity is approximately 50 to 60 days, with the cashew apple maturing about 20 to 30 days after the nut.
Harvesting and Initial Processing
Cashew nuts and apples are harvested when the apple ripens and falls naturally from the tree. Farmers often keep the area beneath the trees clear to easily collect the fallen fruits. The cashew apple is highly perishable, spoiling rapidly within a day or two after falling, which limits its distribution.
After collection, the first step is to separate the cashew nut from the apple. This can be done manually by twisting the nut from the apple or using specialized machines for efficiency. While the cashew apple is edible and used locally for juices, jams, or fermented beverages, the primary focus for global trade is the nut.
Following separation, the raw cashew nuts, still in their shells, undergo initial drying. This process, often done by sun-drying for several days, reduces the moisture content to below 9%, preventing mold growth and preparing them for storage and further processing. This preliminary handling prepares the nuts for industrial steps like roasting, shelling, and peeling, which remove the toxic shell and reveal the edible kernel.