A hazelnut is the nut of the hazel and is also known as cobnut or filbert nut according to species. A cob is roughly spherical to oval, about 15–25 mm long and 10–15 mm in diameter, with an outer fibrous husk surrounding a smooth shell. A filbert is more elongated, being about twice as long as it is round. The nut falls out of the husk when ripe, about seven to eight months after pollination. The kernel of the seed is edible and used raw or roasted, or ground into a paste. Hazelnuts are also used for livestock feed, as are chestnuts and acorns. The seed has a thin, dark brown skin, which is sometimes removed before cooking.

Hazelnuts are produced in commercial quantities in Turkey, Italy, Greece, Georgia, in south of the Spanish region of Catalonia, in the UK county of Kent and in the American states of Oregon and Washington. Turkey is the largest producer of hazelnuts in the world with approximately 75% of worldwide production.

Hazelnuts are used in confectionery to make praline, and also used in combination with chocolate for chocolate truffles and products such is Nutella and Frangelico liqueur. Hazelnut oil, pressed from hazelnuts, is strongly flavored and used as cooking oil.

Hazelnuts are rich in protein and unsaturated fat. Moreover, they contain significant amounts of thiamine and vitamin B6, as well as smaller amounts of other B vitamins.

Because hazelnuts do not generally need to be toasted, indeed Kentish Cobnuts are still traditionally sold fresh, it has been speculated this was done to make them more digestible for children. Toasting the nuts also was thought to increase how long they would keep, and they have historically been a useful food for mariners because they keep well.

Hazel has been grown historically in coppices for use in wattle and daub buildings, and in hedges. The Romans cultivated hazelnuts including in Britain, although there is no evidence that they spread specific cultivars. Cultivated varieties have been grown since at least the 16th century, with a great increase in varieties during the 1800s; in particular, the first really widespread cultivar, the Kentish Cobnut, was introduced in 1830.

The traditional method to increase nut production is called 'butting', which involves prompting more of the trees' energy to go into flower bud production, by snapping but not breaking off the tips of the New Year’s shoots six or seven leaf groups from the join with the trunk or branch, at the end of the growing season. The traditional term for an area of cultivated hazelnuts is a plat.

Hazelnuts are harvested annually in midautumn. As autumn comes to a close, the trees drop their nuts and leaves. Most commercial growers wait for the nuts to drop on their own, rather than use equipment to shake them from the tree.

Four primary pieces of equipment are used in commercial harvesting: the sweeper, the harvester, the nut cart and the forklift. The sweeper moves the nuts into the center of the rows, the harvester lifts and separates the nuts from any debris, the nut cart holds the nuts picked up by the harvester, and the forklift brings a tote to offload the nuts from the nut cart and then stacks the totes to be shipped to the processor (nut dryer). The sweeper is a low-to-the-ground machine that makes two passes in each tree row. It has a 2 m belt attached to the front that rotates to sweep leaves, nuts, and small twigs from left to right, depositing the material in the row's center as it drives forward. On the rear of the sweeper is a powerful blower to blow material left into the adjacent row with air speeds up to 90 m/s. Careful grooming during the year and patient blowing at harvest can eliminate the need for hand raking around the trunk of the tree, where nuts can accumulate. The sweeper prepares a single center row of nuts narrow enough for the harvesting tractor to drive over without driving on the center row. It is best to only sweep a few rows ahead of the harvesters at any given time, to prevent the tractor that drives the harvester from crushing the nuts that may still be falling from the trees. Hazelnut orchards may be harvested up to three times during the harvest season, depending on the quantity of nuts in the trees and the rate of nut drop as a result of weather.

Uses

 

Hazelnuts have a significant place among the types of dried nuts in terms of nutrition and health because of the special composition of fats (primarily oleic acid), protein, carbohydrates, vitamins (vitamin E), minerals, dietary fibers, hazelnuts are currently eaten raw, roasted, blanched, minced, sliced, powdered and pureed. Hazelnuts are also used as a premium ingredient in chocolates, biscuits, confectionary products, sweets, pastries and ice cream and in meals and salads. Hazelnuts have not yet reached their full potential in the United States. With much wider sustainable production, they could be a main component of a healthy diet. Many top chefs are choosing to include hazelnuts in more and more recipes and dishes because of their excellent flavor and health value.