Nut (seed)

A nut is a seed that consists of a single soft portion known as the kernel surrounded by an indehiscent hard covering or shell. True nuts are produced by angiosperms (flowering trees) and can range in size from the small nutlets of the beech tree (also known as beechmasts) to the giant double coconuts of the coco de mer tree (Lodoicea maldivica[?]). Some nuts are borne within fruits, whose fleshy part may be called a husk or hull. Small nuts are called nutlets.

As large nuts are resource-intensive to produce, they are borne exclusively by trees, usually in forests. The large supply of energy in a nut allows a seedling tree to grow for a long time before reaching light, an adaptation to shady forests.

Nuts as food

Nuts as food are a more restrictive category than nuts in botany. The term is restricted to large oily or starchy seeds that are edible raw. It also includes some seeds that botanists do not consider nuts.

Nuts generally have a high oil content which makes them a prised food and energy source. A large number of nuts are edible by humans and used in cooking, eaten raw, sprouted, or roasted as a snack food, or pressed for oil that is used in cookery and cosmetics. Other nuts are a significant source of nutrition for wildlife. This is particularly true in temperate climates where animals such as the squirrel store acorns and other nuts during the autumn to keep them going during the winter and early spring.

Nuts of temperate climates are dominated by wind-pollinated trees of the order Fagales:

• acorn, the seed of the oak tree
• beech
• chestnut
• hazelnut[?] or filbert, the seed of the hazel and cob trees
• hickory
• pecan
• walnut, which includes English or Persian walnut, black walnut, heartnut, and butternut

Most types of acorns are too bitter to eat unless leached, on account of tannins. Despite this disadvantage, acorns are an important food in many regions.

Other temperate nuts:

• almond
• apricot (some varieties)
• pistachio

The nut of the horse-chestnut (Aesculus hippocastanum) is also known as a conker[?]. Conkers are inedible but are collected and used in an old children's game, also known as conkers[?], in which a nut is threaded onto a strong cord and then each child attempts to break their opponent's conker by hitting it with their own. Related species, Aesculus californica, was formerly eaten by the Native Americans of California in times of famine. It must be leached to remove poisonous constituents before eating.

Tropical nuts:

• areca (or betel nut)
• brazil nut[?]
• cashew
• coconut
• macadamia nut[?]

Some nuts that are not true nuts in the botanical sense:

• peanut, actually a bean, the seed of a legume
• pine put[?] or piñon, the seed of a gymnosperm[?]