Cashew

Cashew is a frost-tender perennial always raised as transplanted seedlings, since it can only be grown where freezing weather never occurs. Trees grow best between about 20°C and 30°C, with growth slowing below 20°C and fruit set harmed if temperatures exceed 36°C during flowering and fruiting; the crop tolerates annual rainfall from as little as 400 mm to as much as 4,000 mm and can be sited anywhere from sea level to 1,000 m elevation, aided by a deep taproot and wide-spreading lateral roots that carry it through dry spells.

Flowering: Flowering runs from December to April north of the equator and from June to December south of it, peaking between September and November in the Southern Hemisphere. The tree is cross-pollinated and produces three to four separate flushes of flowers and fruit within a three- to four-month span, so a single planting yields fruit over an extended period rather than in one narrow season.

Nuts are picked only once the cashew apple beneath them has fully ripened, and picking is timed to dry weather since damp conditions spoil the crop. Because flowering and fruiting occur in three or four separate flushes across three to four months, harvesting is repeated through the season rather than done in a single pass, and since the nut stays firmly fixed to the apple, cashew apples make up the bulk of what is physically gathered.

Storage: The cashew apple bruises and spoils quickly, which confines its fresh use mainly to producing regions such as Brazil, Mozambique, and Indonesia, while the harder-shelled true nut is kept until it can be processed and shelled for its kernel.

Culinary: The kernel is the crop's principal product, eaten roasted or steamed as a snack, ground into cashew butter, or used in confectionery and cooking. The cashew apple is pressed for fresh or fermented juice and cooked down into jams, jellies, syrups, and preserves in the areas where it is grown.

Fodder: Kernels rejected after roasting, along with cashew apple pulp and bagasse left from juice extraction, oil cake from kernel oil pressing, and the red kernel skins removed during confectionery preparation, are all fed to livestock.

Industrial: The caustic liquid drawn from inside the nut's shell, cashew nut shell liquid, is used to make varnishes, lubricants, cements, and friction materials, drawing on the polymerizing phenolic compounds anacardic acid, cardol, and cardanol that it contains.

Medicinal: Traditional ethnomedicine has drawn on nearly every part of the cashew tree, according to historical accounts, though the specific conditions or preparations involved are not detailed in that record.

Cashew originated in tropical South America, native to Brazil's northeastern moist forests, the savannas of the Amazon Basin, and the grassland plains of Colombia and Venezuela. Portuguese traders carried the crop from Brazil to their colonies in Africa and Asia alongside coffee and tea, introducing it to Goa, India between 1560 and 1565, while Spanish colonizers are credited with spreading it northward into Central America. Early cultivators in Goa valued the tree for its fruit and for its usefulness against coastal soil erosion, but cashew did not develop into a large-scale commercial industry until the 1930s.