# Hazel

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{{Short description|Genus of trees}}
{{Other uses}}
{{Automatic taxobox
|name = Hazels
|image = Corylus avellana 0001.JPG
|image_caption = [Common hazel](/source/Corylus_avellana) (''Corylus avellana'')
|taxon = Corylus
|authority = [L.](/source/Carl_Linnaeus)
|type_species = ''[Corylus avellana](/source/Corylus_avellana)''
|type_species_authority = [L.](/source/L.)
|subdivision_ranks = Species
|subdivision = See text for species.
|synonyms_ref = <ref>{{cite web |title=''Corylus'' L. |url=https://powo.science.kew.org/taxon/urn:lsid:ipni.org:names:13489-1 |date=2025 |website=Plants of the World Online |publisher=Royal Botanic Gardens, Kew |access-date=17 November 2025 }}</ref>
|synonyms = ''Lopima'' <small>Dochnahl</small>
}}
[[File:Catkins Corylus avellana-Mont Bart-5124~2015 12 26.JPG|thumb|right|Young male catkins of ''[Corylus avellana](/source/Corylus_avellana)'']]

'''Hazels''' are plants of the genus '''''Corylus''''' of [deciduous](/source/deciduous) [tree](/source/tree)s and large [shrub](/source/shrub)s native to the [temperate](/source/temperateness) Northern Hemisphere. The genus is usually placed in the [birch](/source/birch) family, [Betulaceae](/source/Betulaceae),<ref name=grin>Germplasmgobills Information Network: [http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?2962 ''Corylus''] {{Webarchive|url=https://web.archive.org/web/20090114213945/http://www.ars-grin.gov/cgi-bin/npgs/html/genus.pl?2962 |date=2009-01-14 }}</ref><ref>{{Cite journal|last1=Chen|first1=Zhi-Duan|last2=Manchester|first2=Steven R|last3=Sun|first3=Hai-Ying|date=August 1999|title=Phylogeny and evolution of the Betulaceae as inferred from DNA sequences, morphology, and paleobotany|journal=American Journal of Botany|volume=86|issue=8|pages=1168–1181|doi=10.2307/2656981|issn=0002-9122|jstor=2656981|pmid=10449397|doi-access=free}}</ref><ref name=rushforth>{{cite book |last=Rushforth |first=K. |year=1999 |title=Trees of Britain and Europe |publisher=Collins |isbn=0-00-220013-9}}</ref>{{pn |date=November 2025}}<ref name=rhs>{{cite book| editor-last=Huxley |editor-first=A. |year=1992 |title=New RHS Dictionary of Gardening |publisher=Macmillan |isbn=0-333-47494-5}}</ref>{{pn |date=November 2025}} though some botanists split the hazels (with the [hornbeam](/source/hornbeam)s and allied genera) into a separate family Corylaceae.<ref>{{Cite book|title=Trees and Shrubs Hardy in the British Isles|last=Bean|first=William Jackson|date=1976|publisher=J. Murray|others=Taylor, George|isbn=0719517907|edition=8th|volume=1|location=London|oclc=103403}}</ref><ref>{{cite journal|last1=Erdogan |first1=V. |last2=Mehlenbacher |first2=S. A. |year=2002 |title=Phylogenetic analysis of hazelnut species (Corylus, Corylacae) based on morphology and phenology |journal=Sist. Bot. Dergisi |volume=9 |pages=83–100}}</ref> The fruit of the hazel is the [hazelnut](/source/hazelnut).

== Botany ==
Hazels have simple, rounded [leaves](/source/leaves) with double-serrate margins. The [flower](/source/flower)s are produced very early in spring before the leaves, and are [monoecious](/source/monoecious), with single-sex [catkin](/source/catkin)s. The male catkins are pale yellow and {{Convert|5–12|cm|abbr=off|frac=4}} long, and the female ones are very small and largely concealed in the buds, with only the bright-red, 1-to-3&nbsp;mm-long [styles](/source/Carpel) visible.<ref name=rushforth/>{{pn |date=November 2025}} 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 granular [exine](/source/exine)s bearing three conspicuous pores.<ref>{{Cite journal | doi=10.1038/010355b0| title=Pollen-grains in the Air| journal=Nature| volume=10| issue=253| pages=355| year=1874| last1=Airy| first1=Hubert| bibcode=1874Natur..10..355A| s2cid=4077214| url=https://zenodo.org/record/1429213| doi-access=free}}</ref>

The fruits are [nuts](/source/Nut_(fruit)) {{Convert|1–2.5|cm|abbr=on|frac=4}} long and 1–2&nbsp;cm diameter, surrounded by an [involucre](/source/involucre) (husk) which partly to fully encloses the nut. The shape and structure of the [involucre](/source/involucre), and also the growth habit (whether a tree or a suckering shrub), are important in the identification of the different species of hazel.<ref name=rushforth/>{{pn |date=November 2025}} Kernels of nuts from various cultivars make up between 33.20% to 49.5% of the fruit, especially cultivars grown close to the [Mediterranean Sea](/source/Mediterranean_Sea)<!-- Romana in Italy, Negret & Portet in Spain, Çakıldak & Tombul in Turkey -->.<ref>{{cite journal |last1=Król |first1=Katarzyna |last2=Gantner |first2=Magdalena |title=Morphological Traits and Chemical Composition of Hazelnut from Different Geographical Origins: A Review |journal=Agriculture |date=August 2020 |volume=10 |issue=9 |pages=375–391 |doi=10.3390/agriculture10090375 |bibcode=2020Agric..10..375K |doi-access=free }}</ref>{{rp|377-378}}

Fossils date back to the [Cretaceous](/source/Cretaceous),<ref>{{cite journal |last1=Norton J.H.;Hall, N.J. |title=Palynology of the Upper Cretaceous and Lower Tertiary in the type locality of the Hell Creek Formation, Montana, USA |journal=Palaeontographica Abteilung B |date=1969 |volume=125}}</ref> and it was likely part of the diet of certain [dinosaurs](/source/dinosaurs).<ref>{{cite web |title=A triceratopsian diet |url=https://www.mcgill.ca/redpath/article/triceratopsian-diet |website=Mcgill.ca}}</ref>

==Species==
''Corylus'' has around 14–18 species. The circumscription of species in [eastern Asia](/source/eastern_Asia) is disputed, with [World Flora Online](/source/World_Flora_Online) <!-- replaced ''WCSP''--> and the ''Flora of China'' differing in which taxa are accepted, within this region. WFO accepts 17 species while Flora of China accepts 20 species (including ''Corylus mandshurica'').

Only those taxa accepted by both sources are listed below.<ref name="WorldFloraOnline">{{cite web |title=''Corylus'' L. |url=https://www.worldfloraonline.org/taxon/wfo-4000009390 |access-date=19 October 2023}}</ref><ref name=foc>{{cite web |title=''Corylus'' in Flora of China @ efloras.org |url=http://www.efloras.org/florataxon.aspx?flora_id=2&taxon_id=108088 |website=www.efloras.org |access-date=19 October 2023}}</ref><ref name=fna>Flora of North America: [http://www.efloras.org/florataxon.aspx?flora_id=1&taxon_id=108088 ''Corylus'']</ref>

The species are grouped as follows:
* Nut surrounded by a soft, leafy [involucre](/source/Involucral_bract), multiple-stemmed, suckering [shrub](/source/shrub)s to 12 m tall
** Involucre short, about the same length as the nut
*** ''[Corylus americana](/source/Corylus_americana)'' – American hazel, eastern [North America](/source/North_America)
*** ''[Corylus avellana](/source/Corylus_avellana)'' – Common hazel, [Europe](/source/Europe) and [western Asia](/source/western_Asia)
*** ''[Corylus heterophylla](/source/Corylus_heterophylla)'' – Asian hazel, [Asia](/source/Asia)
*** ''[Corylus yunnanensis](/source/Corylus_yunnanensis)'' – Yunnan hazel, central and southern [China](/source/China)
** Involucre long, twice the length of the nut or more, forming a 'beak'
*** ''[Corylus colchica](/source/Corylus_colchica)'' – Colchican filbert, [Caucasus](/source/Caucasus)
*** ''[Corylus cornuta](/source/Corylus_cornuta)'' – Beaked hazel, North America
*** ''[Corylus maxima](/source/Corylus_maxima)'' – Filbert, [southeastern Europe](/source/southeastern_Europe) and [southwest Asia](/source/southwest_Asia)
*** ''[Corylus sieboldiana](/source/Corylus_sieboldiana)'' – Asian beaked hazel, [northeastern Asia](/source/northeastern_Asia) and [Japan](/source/Japan) (syn. ''C. mandshurica'')
* Nut surrounded by a stiff, spiny involucre, single-stemmed [tree](/source/tree)s to 20–35 m tall
** Involucre moderately spiny and also with glandular hairs
*** ''[Corylus chinensis](/source/Corylus_chinensis)'' – Chinese hazel, western China
*** ''[Corylus colurna](/source/Corylus_colurna)'' – Turkish hazel, southeastern Europe and [Asia Minor](/source/Asia_Minor)
*** ''[Corylus fargesii](/source/Corylus_fargesii)'' – Farges' hazel, western China
*** ''[Corylus jacquemontii](/source/Corylus_jacquemontii)'' – Jacquemont's hazel, [Himalaya](/source/Himalaya)
*** ''[Corylus wangii](/source/Corylus_wangii)'' – Wang's hazel, [southwest China](/source/southwest_China)
** Involucre densely spiny, resembling a chestnut burr
*** ''[Corylus ferox](/source/Corylus_ferox)'' – Himalayan hazel, Himalaya, [Tibet](/source/Tibet) and southwest China (syn. ''C. tibetica'').

Several [hybrids](/source/Hybrid_(biology)) exist, and they can occur between species in different sections of the genus, e.g. ''[Corylus × colurnoides](/source/Corylus_%C3%97_colurnoides)'' (''C. avellana'' × ''C. colurna'').  The oldest confirmed hazel species is ''[Corylus johnsonii](/source/Corylus_johnsonii)'' found as [fossil](/source/fossil)s in the [Ypresian](/source/Ypresian)-age rocks of [Ferry County, Washington](/source/Ferry_County%2C_Washington).<ref name=Pigg2003>{{cite journal |last1=Pigg |first1=K.B. |author2=Manchester S.R. |author3=Wehr W.C. |year=2003 |title=''Corylus'', ''Carpinus'', and ''Palaeocarpinus'' (Betulaceae) from the Middle Eocene Klondike Mountain and Allenby Formations of Northwestern North America |journal= International Journal of Plant Sciences |volume=164 |issue= 5 |pages=807–822 |doi=10.1086/376816|bibcode=2003IJPlS.164..807P |s2cid=19802370 }}</ref>

Chilean hazel (''[Gevuina avellana](/source/Gevuina_avellana)''), despite its name, is not related to this genus.<ref>{{cite book |last1=Crawford |first1=Martin |title=Shrubs for Gardens, Agroforestry and Permaculture |date=2020 |publisher=Permanent Publications |isbn=978-1-85623-342-2 |language=en}}</ref>

== Ecology ==
At least 21 species of [fungus](/source/fungus) have a mutualistic relationship with hazel. ''[Lactarius pyrogalus](/source/Lactarius_pyrogalus)'' grows almost exclusively on hazel, and hazel is one of two kinds of host for the rare ''[Hypocreopsis rhododendri](/source/Hypocreopsis_rhododendri)''. Several rare species of ''Graphidion'' [lichen](/source/lichen) depend on hazel trees. In the UK, five species of [moth](/source/moth) are specialised to feed on hazel including ''[Parornix devoniella](/source/Parornix_devoniella)''. Animals which eat hazelnuts include [red deer](/source/red_deer), [dormouse](/source/dormouse) and [red squirrel](/source/red_squirrel).<ref>[https://treesforlife.org.uk/forest/species-profiles/hazel/ Trees for Life - Hazel]</ref>

[Myzocallis coryli](/source/Myzocallis_coryli), a European species of aphid uses this genus exclusively as its host plant, and has caused major agricultural damage in Oregon to Hazel farms after its introduction to the United States.<ref>{{Cite web |date=2015-10-22 |title=Hazelnut-Aphid |url=https://pnwhandbooks.org/insect/nut/hazelnut/hazelnut-aphid |access-date=2026-01-06 |website=Pacific Northwest Pest Management Handbooks |language=en}}</ref>

== Uses ==
{{Further|Hazelnut}}[[File:Hazel coppice, Bubbenhall Wood. - geograph.org.uk - 1709242.jpg|thumb|right|Hazel [coppice](/source/coppice) in winter at [Bubbenhall](/source/Bubbenhall) in [Warwickshire](/source/Warwickshire), [England](/source/England)]]
The nuts of all hazels are edible. The [common hazel](/source/common_hazel) is the species most extensively grown for its nuts, followed in importance by the [filbert](/source/Corylus_maxima). Nuts are also harvested from the other species, but apart from the filbert, none is of significant commercial importance.<ref name=rhs/>

A number of [cultivar](/source/cultivar)s of the common hazel and filbert are grown as [ornamental plant](/source/ornamental_plant)s in [garden](/source/garden)s, including forms with contorted stems (''C. avellana'' 'Contorta', popularly known as "Corkscrew hazel" or "[Harry Lauder](/source/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 making [wattle](/source/Wattle_(construction)), [withy](/source/withy) fencing, baskets, and the frames of [coracle](/source/coracle) boats.  The tree can be [coppiced](/source/coppicing),<ref>{{cite web |title=Coppicing |url=https://www.smallwoods.org.uk/en/advice-and-information/the-economics-of/coppicing/ |website=Small Woods |access-date=19 October 2023}}</ref> and regenerating shoots allow for harvests every few years. There is a seven-year cycle (cut and grow) for [hurdle](/source/hurdle) (fence) making.<ref>{{cite web |title=TYPES OF WOODLAND MANAGEMENT |url=https://www.woodlandtrust.org.uk/plant-trees/managing-trees-and-woods/types-of-woodland-management/ |access-date=19 October 2023}}</ref>

Hazels are used as food plants by the [larva](/source/larva)e of various species of [Lepidoptera](/source/Lepidoptera) including ''[Eriocrania chrysolepidella](/source/Eriocrania_chrysolepidella)''.<ref>{{cite web |title=''Paracrania chrysolepidella'' [Lepidoptera: Eriocraniidae] in Leaf and stem mines of British flies and other insects |url=http://www.ukflymines.co.uk/Moths/Eriocrania_chrysolepidella.php |website=www.ukflymines.co.uk |access-date=19 October 2023}}</ref>

==Culture==
{{See also|Salmon of Wisdom|The Boyhood Deeds of Fionn}}
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 by [salmon](/source/salmon) (a fish sacred to [Druid](/source/Druid)s), which absorbed the wisdom. A Druid teacher, in his bid to become [omniscient](/source/Omniscience), 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 called [Fionn Mac Cumhail](/source/Fionn_Mac_Cumhail) (Fin McCool) and went on to become one of the most heroic leaders in [Gaelic mythology](/source/Irish_mythology).<ref name=flz>Floriz: [http://www.floriz.co.uk/knowledge/26-trees/4-mythology-and-folklore-of-the-hazel-tree Mythology and Folklore of the Hazel Tree] {{Webarchive|url=https://web.archive.org/web/20120331024128/http://www.floriz.co.uk/knowledge/26-trees/4-mythology-and-folklore-of-the-hazel-tree |date=2012-03-31 }}</ref>

"The Hazel Branch" from ''[Grimms' Fairy Tales](/source/Grimms'_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.<ref>Pitt.edu https://www.pitt.edu/~dash/grimm021.html June 1, 2011</ref>

The Russian [Oreshnik](/source/Oreshnik_(missile)) ({{langx|ru|Орешник|lit=Hazel tree}}) missile is named for the Hazel tree.<ref>{{cite news |last1=Faulconbridge |first1=Guy |last2=Bobrova |first2=Marina |last3=Rodionov |first3=Maxim |date=21 November 2024 |title=Putin says Russia fired High-hypersonic ballistic missile at Ukraine in warning to the West |url=https://www.reuters.com/world/europe/putin-says-russia-fired-hypersonic-ballistic-missile-ukraine-warning-west-2024-11-21/ |access-date=21 November 2024 |work=[Reuters](/source/Reuters)}}</ref>

==Gallery==
<gallery>
File:Corylus fargesii, Arnold Arboretum - IMG 6165.JPG|Form (Farges' hazel)
File:Hazel Catkins.jpg|Male catkins (common hazel)
File:Hazel Flower Female.jpg|Female flower (common hazel)
File:TurkHazel.jpg|Leaves and nuts with spiny husks (Turkish hazel)
File:Hazelnuts.jpg|[Hazelnuts](/source/Hazelnuts)
File:Hazelnut (male flower), overlay of 7 channel autofluorescence microscopy (30458886372).jpg|Closeup of a male hazelnut flower using [autofluorescence](/source/autofluorescence) microscopy
</gallery>

==References==
{{Reflist}}

==External links==
{{Commons category|Corylus}}
* {{cite web|last=Eichhorn|first=Markus|title=The Hazel Tree|url=http://www.test-tube.org.uk/trees/video_hazel.htm|work=Test Tube|publisher=[Brady Haran](/source/Brady_Haran) for the [University of Nottingham](/source/University_of_Nottingham)|date=December 2010}}

{{Nuts}}
{{Woodworking}}
{{Taxonbar|from=Q145889}}
{{Authority control}}

Category:Corylus
Category:Edible nuts and seeds
Category:Botanical taxa named by Carl Linnaeus

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Adapted from the Wikipedia article [Hazel](https://en.wikipedia.org/wiki/Hazel) by Wikipedia contributors ([contributor history](https://en.wikipedia.org/wiki/Hazel?action=history)). Available under [Creative Commons Attribution-ShareAlike 4.0 International](https://creativecommons.org/licenses/by-sa/4.0/). Changes may have been made.