Botanically, a nut is a one seeded fruit enclosed in a leathery or woody covering, or the pericarp. A nut is classified as an indehiscent fruit, at maturily the pericarp does not to release the seed. The single seed is sometime called as a kernel. The acorn (from oax trees), chestnut, filbert (or hazel nut), pecan and walnut are true nuts are considered nuts for commercial purposes as food. Look also on areca nuts.
Nut cultivation
Nut corps grow primarily in the temperate and tropical regions of the world. Many species form vigorously trees that even without cultivation can compete on marginal land. Some species have been improved through selection and breeding and are subjected to complex cultural systems. Most marketed nuts come from cultivated orchard trees, the Brazil nut, however, is produced only by wild trees, and wild trees contribute to the production of many other species, such as pecan and filbert.
The length of the growing season and the minimum winter temperature are two major limiting factors for nut crop production, because with a few exceptions, such as the Carpathian walnut, which bears even in New England, most commercially important nut trees are sensitive to frost and not survive harsh winters.
Nutrition Content
Green nuts contain 50% or more water when harvested, but must be cured or semidried for proper storage. Fat content varied from about 70% in Macadamia nuts and pecans to 4% in dried chestnuts. Carbohydrates are low in most tree nuts, although chest nuts are high in starch and, ground into a flour, are used in place of cereal in many Mediterranean countries.
Protein content range from approximately 3.4% in the coconut to 30% in the peanut. In general the food energy provided by nuts compares more than favorably with that of meat; about 600 - 700 calories per 100 grams from such nuts as walnuts, almonds, and pecans, compared with about 250 calories per 100 grams from a beefsteak with moderate fat content.