Hazels have simple, roundedleaves with double-serrate margins. Theflowers are produced very early in spring before the leaves, and aremonoecious, with single-sexcatkins. The male catkins are pale yellow and 5–12 centimetres (2–4+3⁄4 inches) long, and the female ones are very small and largely concealed in the buds, with only the bright-red, 1-to-3 mm-longstyles visible.[4][page needed] The pollen of hazel species, which are often the cause for allergies in late winter or early spring, can be identified under magnification (600×) by their characteristic granularexines bearing three conspicuous pores.[8]
The fruits arenuts1–2.5 cm (1⁄2–1 in) long and 1–2 cm diameter, surrounded by aninvolucre (husk) which partly to fully encloses the nut. The shape and structure of theinvolucre, and also the growth habit (whether a tree or a suckering shrub), are important in the identification of the different species of hazel.[4][page needed] Kernels of nuts from various cultivars make up between 33.20% to 49.5% of the fruit, especially cultivars grown close to theMediterranean Sea.[9]: 377–378
Corylus has around 14–18 species. The circumscription of species ineastern Asia is disputed, withWorld Flora Online and theFlora of China differing in which taxa are accepted, within this region. WFO accepts 17 species while Flora of China accepts 20 species (includingCorylus mandshurica).
Only those taxa accepted by both sources are listed below.[12][13][14]
The species are grouped as follows:
Nut surrounded by a soft, leafyinvolucre, multiple-stemmed, suckeringshrubs to 12 m tall
The nuts of all hazels are edible. Thecommon hazel is the species most extensively grown for its nuts, followed in importance by thefilbert. Nuts are also harvested from the other species, but apart from the filbert, none is of significant commercial importance.[5]
A number ofcultivars of the common hazel and filbert are grown asornamental plants ingardens, including forms with contorted stems (C. avellana 'Contorta', popularly known as "Corkscrew hazel" or "Harry Lauder's walking stick" from its gnarled appearance); with weeping branches (C. avellana 'Pendula'); and with purple leaves (C. maxima 'Purpurea').
Hazel is a traditional material used for makingwattle,withy fencing, baskets, and the frames ofcoracle boats. The tree can becoppiced,[18] and regenerating shoots allow for harvests every few years. There is a seven-year cycle (cut and grow) forhurdle (fence) making.[19]
The Celts believed hazelnuts gave one wisdom and inspiration. There are numerous variations on an ancient tale that nine hazel trees grew around a sacred pool, dropping into the water nuts that were eaten bysalmon (a fish sacred toDruids), which absorbed the wisdom. A Druid teacher, in his bid to becomeomniscient, caught one of these special salmon and asked a student to cook the fish, but not to eat it. While he was cooking it, a blister formed and the pupil used his thumb to burst it, which he naturally sucked to cool, thereby absorbing the fish's wisdom. This boy was calledFionn Mac Cumhail (Fin McCool) and went on to become one of the most heroic leaders inGaelic mythology.[21]
"The Hazel Branch" fromGrimms' Fairy Tales claims that hazel branches offer the greatest protection from snakes and other things that creep on the earth. In the Grimm tale "Cinderella", a hazel branch is planted by the protagonist at her mother's grave and grows into a tree that is the site where the girl's wishes are granted by birds.[22]
The RussianOreshnik (Russian:Орешник,lit. 'Hazel tree') missile is named for the Hazel tree.[23]
^abcRushforth, K. (1999).Trees of Britain and Europe. Collins.ISBN0-00-220013-9.
^abHuxley, A., ed. (1992).New RHS Dictionary of Gardening. Macmillan.ISBN0-333-47494-5.
^Bean, William Jackson (1976).Trees and Shrubs Hardy in the British Isles. Vol. 1. Taylor, George (8th ed.). London: J. Murray.ISBN0719517907.OCLC103403.
^Erdogan, V.; Mehlenbacher, S. A. (2002). "Phylogenetic analysis of hazelnut species (Corylus, Corylacae) based on morphology and phenology".Sist. Bot. Dergisi.9:83–100.
^Norton J.H.;Hall, N.J. (1969). "Palynology of the Upper Cretaceous and Lower Tertiary in the type locality of the Hell Creek Formation, Montana, USA".Palaeontographica Abteilung B.125.{{cite journal}}: CS1 maint: multiple names: authors list (link)
^Pigg, K.B.; Manchester S.R.; Wehr W.C. (2003). "Corylus,Carpinus, andPalaeocarpinus (Betulaceae) from the Middle Eocene Klondike Mountain and Allenby Formations of Northwestern North America".International Journal of Plant Sciences.164 (5):807–822.Bibcode:2003IJPlS.164..807P.doi:10.1086/376816.S2CID19802370.
^Crawford, Martin (2020).Shrubs for Gardens, Agroforestry and Permaculture. Permanent Publications.ISBN978-1-85623-342-2.
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