The hazelnut is the fruit of the hazel tree and therefore includes any of the nuts deriving from species of the genus Corylus, especially the nuts of the species Corylus avellana. They are also known as cobnuts or filberts according to species. Hazelnuts are used as a snack food, in baking and desserts, and in breakfast cereals such as muesli. In confectionery, they are used to make praline, and also used in combination with chocolate for chocolate truffles and products such as chocolate bars and hazelnut cocoa spreads such as Nutella. They are also used in Frangelico liqueur. Hazelnut oil, pressed from hazelnuts, is strongly flavored and high in monounsaturated fat. It is used as a cooking oil and as a salad or vegetable dressing. In 2023, Turkey was the world's largest producer of hazelnuts, accounting for 57.7% of total production.
Description
A hazelnut cob is roughly spherical to oval, about 15–25 millimetres (5⁄8–1 inch) long and 10–15 mm (3⁄8–5⁄8 in) in diameter, with an outer fibrous husk surrounding a smooth shell, while a filbert is more elongated, being about twice as long as its diameter. The nut falls out of the husk when ripe, about seven to eight months after pollination. The seed is edible and consumed raw, roasted, or ground into a paste. The seed has a thin, dark brown skin, which is sometimes removed before cooking. Nuts make up between 33.2% to 49.5% of the fruit, depending on the cultivar grown. Cultivars close to the Mediterranean Sea have the largest nut to fruit ratio.
Cultivation
History In 1995, evidence of large-scale Mesolithic nut processing, some 8,000 years old, was found in a midden pit on the island of Colonsay in Scotland. The evidence consists of a large, shallow pit full of the remains of hundreds of thousands of burned hazelnut shells. Hazelnuts have been found on other Mesolithic sites, but rarely in such quantities or concentrated in one pit. The nuts were radiocarbon dated to 7720±110 BP, which calibrates to c. 6000 BCE. Similar sites in Britain are known only at Farnham in Surrey and Cass ny Hawin on the Isle of Man. This discovery provides insight into communal activity and planning during the period. The nuts were harvested in a single year, and pollen analysis suggests that all of the hazel trees were cut down at the same time. The scale of the activity and the scarcity of large game on the island suggest that Colonsay may have supported a community with a largely vegetarian diet during their time on the island. Originally, the pit was on a beach close to the shore and was associated with two smaller, stone-lined pits whose function remains obscure, a hearth, and a second cluster of pits. The traditional method to increase nut production is called brutting, which involves prompting more of the tree's energy to go into flower bud production by snapping, but not breaking off, the tips of the new year shoots six or seven leaf groups from where they 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.
Cultivars The many cultivars of the hazel include 'Atababa', 'Barcelona', 'Butler', 'Casina', 'Clark', 'Cosford', 'Daviana', 'Delle Langhe', 'England', 'Ennis', 'Halls Giant', 'Jemtegaard', 'Kent Cob', 'Lewis', 'Tokolyi', 'Tonda Gentile', 'Tonda di Giffoni', 'Tonda Romana', 'Wanliss Pride', and 'Willamette'. Some of these are grown for specific qualities of the nut, including large nut size or early or late fruiting, whereas others are grown as pollinators. The majority of commercial hazelnuts are propagated from root sprouts. Some cultivars are of hybrid origin between common hazel and filbert. In Ireland and the United Kingdom, hazelnuts are sometimes referred to as cobnuts, for which a specific cultivated variety – Kentish cobnuts – is the main variety cultivated in fields known as plats, hand-picked, and eaten green. According to the BBC, a national collection of cobnut varieties exists at Roughway Farm, near Plaxtol in Kent. They are called cobnuts because cob was a word used to refer to the head or "noggin," and children had a game in which they would tie a string to a hazelnut and use it to try to hit an opponent on the head.
Cropping system In Europe hazelnuts are traditionally grown as multi-trunk trees where the rootstock is formed by the variety itself. To enhance the possibility for mechanization and to prevent suckering, a single-trunk tree can be formed by grafting a scion of the desired variety on a Corylus colurna rootstock. There are different approaches in orchard floor management. Strong infestations of certain weeds can lower the yield. Therefore, to prevent yield loss by competition, herbicides are used to create bare soil. Using cover crops protects the soil and suppresses weed establishment without a yield reduction. Silvopastoral systems where animals like pigs are kept in the orchard or silvoarable systems where crops are grown between the rows could introduce new sources of revenue into the hazelnut production and may have beneficial effects on hazelnut yield by fertilizing the soil through nitrogen fixation or animal dung. These systems limit the plant protection measures, potentially impacting the yield quality and level. There are very few studies on these systems, leading to a higher uncertainty for the producer.
Harvesting
Hazelnuts are harvested annually in mid-autumn. As autumn comes to a close, the trees drop their nuts and leaves. Most commercial growers wait for the nuts to drop rather than using equipment to shake them from the tree. The harvesting of hazelnuts is performed either by hand or by manual or mechanical raking of fallen nuts. 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 (i.e., twigs and leaves), 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).
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