Common hazel ( Corylus avellana ), illustration
The European hazel ( Corylus avellana ), and hazel or hazel called, is a plant type from the family of Birch Family (Betulaceae). It is a deciduous shrub that usually reaches a height of around five meters and is native to Europe and Asia Minor and very common in Central Europe. It is known for its edible fruit, hazelnuts , which have been used by humans for thousands of years . The majority of the hazelnuts available on the market, however, come from the closely related Lambert's hazel ( Corylus maxima ).
The epithet avellana refers to the ancient Italian city of Abella , today Avella , in today's province of Avellino in Campania near Mount Vesuvius . The region has been known for its hazelnut cultivation since ancient times.
The hazel usually grows as a multi-stemmed, upright shrub five to six meters high. The branching is sympodial . In rare cases it grows as a tree and then reaches a height of ten meters. It is summer green and forms stick rashes . At the base of the trunk, saplings develop that can grow to several meters high in the first year, but only branch out in the second year and even later bend to the side. These shoots ensure the bush-like growth, as the branching of the hazel is otherwise acrotonic (at the tip). The trunk diameter ( BHD ) can reach 15 to 18 centimeters. The maximum age of the hazel is 80 to 100 years.
Buds and shoots
The winter buds are bluntly egg-shaped, five to seven millimeters long and slightly compressed on the sides. The buds are ciliate on the edge. On the light side they are red-brown, in the shade they are green. The apparent terminal buds are broadly ovate and only barely larger than the side buds.
Young shoots are round in cross-section and have a small, round pith . The shoots are densely covered with short hairs and also have several large, bright lenticels . The shoot tip is characterized by red-brown glandular hairs. Five vascular bundles are visible in the leaf scars. The young shoots are relatively thin and grow somewhat zigzag.
The leaves are alternating in two rows on the shoots, but spiral on upright shoots. The petiole is half to two inches long and hairy glandular. The leaf blade is wrinkled, seven to thirteen inches long and six to ten inches wide. The shape is round to obovate. The spade tip is a short tip, the leaf base is often somewhat asymmetrical and heart-shaped. The leaf margin is roughly double serrated. The upper side of the leaf is hairy and distinctly darker than the underside. The two small, egg-shaped stipules soon fall off after the leaves emerge.
Sun and shadow leaves differ in their anatomy. The less light a leaf receives, the shorter the palisade cells are . In autumn the leaves turn yellow from the edge before they fall off.
Wood and bark
The hazel does not form a bark . Its finishing tissue, even on old twigs, is smooth, glossy gray-brown bark . On top of it sit transverse, bright lenticels . The bark develops longitudinal cracks with age.
The hazel is monoecious , i. H. one plant has female and male inflorescences . These are in dichasial partial inflorescences. The latter are either too many and form catkins (male flowers) or there are several and remain enclosed by the bud (female flowers). The hazel has its flowering time in February / March before the leaves shoot and, as an early bloomer, is an important supplier of pollen for honey bees. On warm, sunny winter days, however, only the male kittens are flown to, as the female flowers neither smell nor offer nectar. Pollination is always done by the wind ( anemophilia ), so the flowers are quite inconspicuous. A single kitten contains around 2 million pollen grains. The bushes bear fruit for the first time when they are around ten years old. With the hazel blossom that is easy to observe, it is a phenological indicator plant .
The male inflorescences emerge in autumn of the previous year and overwinter naked. Usually there are two to four inflorescences at the tip or in the leaf axils of last year's shoots. When they bloom, they stretch to eight to ten centimeters in length. The single flowers are in the axilla of a downy, hairy bract , and two bracts are attached to the peduncle . A perianth is missing, so that the flower consists of four stamens with two anthers each. The pollen of the hazel has three germination pores.
The female flowers are in two-flowered dichasias . Several of these form the female inflorescence, which, however, remains enclosed by the bud scales even during flowering. Only the red scars protrude from the bud. The dichasium consists of the bract, the two pre-leaves of the missing central flower, and the two side flowers that are developed. The side flowers are surrounded by two intergrown bracts, which later become the fruit envelope. The flower consists of the pistil , which consists of two fused carpels . The ovary is divided by partition walls (septa) into two compartments each of which an ovule contains. Usually only one ovule develops.
The climate change affects the heyday of hazel. Under the influence of the progressive overheating of the earth's climate system, the hazel blossom tends to set in earlier and earlier. For example, in 2018 the hazel was already in bloom at the end of January, 22 days earlier than in the early 1950s.
|Nutritional value per 100 g of hazelnut kernels|
|Calorific value||2685 kJ (650 kcal)|
|- of which sugar||1 g|
|- fiber||8.6 g|
|- saturated fat||4.5 g|
|- monounsaturated||46 g *|
|- polyunsaturated||8 g *|
|Vitamins and minerals|
|Vitamin A||5 µg|
|Vitamin B 1||0.6 mg *|
|Vitamin B 2||0.11 mg *|
|Vitamin B 3||1.8 mg *|
|Vitamin B 6||0.6 mg *|
|Vitamin B 9||113 μg *|
|vitamin C||3 mg|
|Vitamin E.||26.6 mg|
|Calcium||114 mg *|
|iron||4.7 mg *|
|phosphorus||290 mg *|
|potassium||680 mg *|
After fertilization , the partitions of the ovary are reduced, a single-seeded nut fruit develops . Both ovules rarely develop into seeds. The two pre-leaves of the flower develop into the fruit envelope, the cupula , which is bell-shaped in the common hazel and has a torn, toothed edge. The rounded mark on the underside of the fruit is the former attachment point to the cupula. The side of the nut is slightly compressed. There is a slight, longitudinally oriented depression on the flat side. These are the commissures, the places where the two carpels meet. Each nut half has a slight elevation on the narrow side: this is the median of each carpel. This is the easiest place to split the nut.
Inside the nut there is a single large seed with no endosperm . The seed coat (testa) is thin and membranous. The columella rests on one narrow side: this is the central column of the ovary, which in the ripe fruit extends from the basal attachment point to the tip of the seed. It is the link between the mother plant and the seed. The axial body of the embryo is accordingly located on the tip side of the seed, the cotyledons fill the remaining part of the seed. They are storage organs that mainly store fatty oils.
The seeds of the hazelnut contain around 60% fatty oil. 100 grams contain around 2700 kJ of energy. See also the information box on the right.
Studies on the ingredients of raw Italian hazelnuts or a roasted hazelnut material made from them found 37 odor-active compounds in the raw nuts, while 46 flavor compounds were detected in the roasted nut material. Filberton , for example, is one of the most important aromatic substances.
The nuts are spread by small mammals ( squirrels , dormice , mice ) and birds ( nuthatches and jays ). These animals use the nuts as food, through lost nuts and forgotten hiding places for food, they also ensure that the seeds spread. Harvest time is usually September / October.
Roots and mycorrhiza
The hazel has a very intensely branched root system. In addition to a taproot , it forms strong side roots that are close to the surface, but not very far. The densest rooting is at a depth of 30 to 40 centimeters. The mean root length of hazels in field hedges is three, a maximum of four meters. Therefore, the hazel has hardly any negative influence on neighboring crops. The hazel forms an ecto mycorrhiza with the following fungi : black truffle ( Tuber melanosporum ), summer truffle ( Tuber aestivum ), winter truffle ( Tuber brumale ); but also pearl mushroom ( Amanita rubescens ), boletus ( Boletus edulis ) and Cenococcum geophilum . The hazel milkling also forms a mycorrhiza with the hazel.
The number of chromosomes is 2n = 22, less often 44.
Distribution and flora history
The area of the hazel covers large parts of Europe as well as Anatolia and the Caucasus . A high density of hazelnut plantations can be found predominantly on the Black Sea coast in northern Anatolia - in the provinces of Zonguldak to Giresun . In the north the distribution area extends to the Orkney Islands and in Norway to the Arctic Circle . In Sweden the hazel occurs up to the 64th, in Finland up to the 63rd parallel. It is not entirely certain whether the hazel occurs naturally in North Africa and Syria .
The hazel occurs in the south of the distribution area up to much higher altitudes than in the north. The altitude limit in the Ore Mountains and in the Vosges is 800 m, in the northern Alps mostly 1200 m, in Carinthia 1600 m and in North Macedonia 1500 m. In the Allgäu Alps, it rises in the Tyrolean part on the Heuberg near Häselgehr up to 1500 meters above sea level.
The hazel has been known as a fossil since the Pliocene . She survived the last ice age in a retreat in south-west Europe, u. a. in northern Portugal. At the beginning of the early warm period ( Boreal ) it migrated from there to Central Europe . It replaced the pine and birch here . From 7000 to 6000 BC During the Middle Stone Age , the hazel was the dominant wood in Central Europe. Then it was pushed back in Central Europe by mixed oak forests . Around 5000 BC The hazel reached southern Sweden, 2000 BC. The upper Volga .
The hazel grows preferentially in oceanic and sub- oceanic climates in warm summer locations. It grows in sparse forests, on forest edges and field hedges . It is a light plant , but also tolerates moderate shade. According to the Ellenberg classification, it is indifferent to moisture, soil reaction and nitrogen demand. It achieves its optimum on moist, well-ventilated, warm soils that have a high humus content and a neutral to alkaline reaction . It does not thrive on nutrient-poor sands or on acidic, wet locations.
In terms of plant sociology, it occurs in Central Europe mainly in oak-hornbeam forests ( Carpinion betuli ) and in alluvial forests ( Alno-Ulmion ). It has optimal conditions in older sloe bushes (Prunetalia stages) on potential beech forest sites (Fagion or Fagetalia). It also forms its own Corylus avellana (Tilio-Acerion) societies on open block rubble, the hazel bush forest: they were described from Carinthia, for example.
There are a myriad of different insect species that feed on the leaves, fruits or the juice of the common hazel, among other things. This also includes some species that live exclusively on this plant monophag . Examples are the hazelnut borer ( Curculio nucum ), cicadas such as the hazel mask cicada ( Oncopsis avellanae ), ox leaf cicada ( Edwardsiana avellanae ) or the thorn leaf cicada ( Edwardsiana spinigera ) and plant lice such as Myzocallis coryli or the hazelnut aphid ( Corylobium ).
The powdery mildew Phyllactinia guttata lives on leaves of hazelnut. The rust fungus Melampsoridium carpini , which normally occurs on hornbeam, is also said to occur on the hazel in the Caucasus. The hazel bran- cupling lives on dead branches of the hazel, while the hazel sprout ( Dichomitus campestris ) lives on dead branches and trunks .
One can distinguish between two varieties:
- Corylus avellana var. Avellana : It occurs from Europe to the Caucasus.
- Corylus avellana var. Pontica (K.Koch) HJPWinkl .: It occurs in northern Turkey and in western Transcaucasia.
The common hazel is not of great importance for forestry . Their high demands on soil strength make them unsuitable for filling the gaps in the crops on poorer soil. Only as mixed wood in the oak coppice forest (oak peeling forest) does it often serve well; Their heavy leaf loss leads to abundant humus in the soil.
Until the beginning of the 20th century, the hazelnut wood was used by hoop cutters to make the hoops. Strong young rods are used as sticks, latticework, flower sticks, etc., in the past also for bird loops, knocking sticks and basket hangers, and stronger branches for walking sticks and crossbow bows. The wood is soft and easy to split, but not very durable. It is used for carpentry work , earlier also for throwing spear shafts . It is more often split and the shavings used for braiding. The charcoal is used as drawing charcoal , but also for the production of gunpowder .
|Harvest quantities 2018 (in t, with shell)
hazelnuts and lambert nuts
|People's Republic of China||24,790|
Even in the early Mesolithic , the hazelnut made an important contribution to human nutrition. The extremely rapid spread in this age is associated with the immigration of humans, who consciously or unconsciously accelerated this by building up hazelnut stocks.
The "hazelnuts" available in stores nowadays are mostly the nuts of the Lambert's rabbit ( Corylus maxima ). In trade, the name hazelnut is used for the fruits of both types, the common hazel and the Lambert hazel. Therefore there are no separate harvest statistics. Since genetic analyzes do not allow a differentiation between Corylus avellana and Corylus maxima (as well as the Corylus pontica Koch. And Corylus colchica Alb., Which some authors also differentiate ), the morphological features merge seamlessly and the forms can be freely crossed with one another, most recent authors consider all of these forms, however, as variants of a single broad species Corylus avellana . The Turkish varieties and cultivars differ from the Mediterranean and Western European mostly in their rather prostrate, ascending growth and a continuous fruit shell that envelops the ripe nut.
In 2018 the world harvest of hazelnuts was 863,888 tons. The ten largest producers (see table) produced 96.7% of the total harvest. In Europe, Italy, France and Spain produced the largest quantities.
Within a 10-year period, the largest harvest was achieved in 2008 with 1,068,329 tons. The harvest in 2014, according to the World Food Organization (FAO) totaling 707,894 tons, was the lowest in this period. This year, unfavorable climatic conditions with frost in the Turkish Black Sea region, the main cultivation area, led to a significant harvest decline to around 450,000 tonnes and the subsequent, sometimes violent, price increases. For 2015, 646,000 tons of nuts were harvested here again, significantly increasing the harvest. In 2016, even fewer hazelnuts (420,000 t) were harvested there than in 2014.
Due to the fluctuating yields, Turkey reintroduced price guarantees for the best qualities without quantity restrictions in 2016 . In Turkey, small plots on slopes that were hardly suitable for machine cultivation were still common in 2017.
The largest hazelnut exporters in 2017 were the USA , France and China . With a share of 71.4% of the global export volume, US hazelnut exports determine the world market price. The largest consumers of hazelnuts are the Swiss with a consumption of 2.1 kilograms per capita per year.
For industrial processing ( roasting ), round cores with a diameter between 9 and 13 mm are required. Industrial nuts can also be roasted and easily dissolve the skin. The chopped nuts or the hazelnut oil obtained from them are used for baked goods, sweets ( nougat , brittle ) and for ice cream.
The roasting enhances the nougat taste; for white nougat the core layers are removed.
There are numerous cultivars that have emerged from selected clones from wild populations and are propagated vegetatively. Some cultivars are also the result of sexual crosses between such varieties, and some are the result of crosses of different species. The cultivars of the Black Sea and Caucasus region and those of the Mediterranean region are genetically (and also morphologically) clearly separated from each other and go back to independent domestication events. Among the Turkish cultivars, the national Hazelnut Research Institute in Giresun distinguishes 16 main varieties and numerous other local cultivars and regional varieties , these are divided into three groups according to the shape of the nuts, those with round, with pointed and with almond-shaped nuts. The round shapes are particularly important for industrial use and export. The most important variety is Tombul , other common varieties are Cakildak , Cavcava , Fosa , Kan , Karafindik , Kargalak , Mincane , Palaz . The pointed varieties that are considered to be of lesser quality are Aci , Incekara , Kalinkara , Kus and Sivri . Important varieties in Oregon (USA) are Ennis , Butler and Barcelona , in Viterbo (Italy) Tonda Romana and in Germany the Hallesche giant nut or the Zeller nut . There are also differences between the varieties in terms of ecological requirements, disease resistance ( Xanthomonas arboricola ), possible uses and yields. The propagation usually takes place via vegetative propagation, mainly by rooting cuttings , subsidence and grafting . For the latter, the tree hazel ( Corylus colurna ) is often used as a base, as it is easy to care for and harvest with its trunk.
In addition, some varieties are grown in gardens:
- The corkscrew hazel ( Corylus avellana 'Contorta') - presumably a spontaneous mutation , discovered in England around 1900, is characterized by its corkscrew-like twisted branches, which are used for cutting vases in winter. It becomes 3 to 5 m high and 2 to 4 m wide, the nuts are smaller and not as numerous as in the species.
- The leaves of the 'Aurea' variety are yellow when they shoot and later turn yellow-green.
- Corylus avellana 'Red Majestic' - red-leaved form of the corkscrew hazel, growing slightly weaker than this.
Hazelnut leaves ( Folia Coryli avellanae ) are used as medicinal products . They contain 0.04% essential oil , palmitic acid , paraffin , myricitroside , sucrose , taraxerol and β-sitosterol . They are used in tea mixtures as a substitute for leaves of Hamamelis virginiana .
The bud deformations caused by the hazelnut gall mite ( Phytoptus avellanae ) are remarkable . On nutrient-rich soils, the roots are occasionally occupied by the fully parasitic scale root ( Lathraea squamaria ). The nuts are often attacked by the larvae of the hazelnut borer ( Curculio nucum ), which eat the seeds.
The hazel is a symbol of the fertility of life and love; Immortality; Spring and happy beginning; Wish fulfillment; Luck. Like the black elder, it has a long cultural tradition in Central Europe. Hazel branches were often part of both pagan and Christian grave finds.
As a very old food, the hazel was likely to have had a high priority in Stone Age cultures. At least from Germanic times it has been handed down that "Frau Haselin" was not allowed to be felled. Strangers were not allowed to take more than a handful of nuts from hazel bushes.
In ancient Rome , the hazel was a symbol of peace. Negotiators in armistice and peace negotiations had a hazel branch in hand as a sign of their good intentions. Even in historical times were in Germany grinding and Gerichtsstätten with the "Summer battens", the Johannis instincts of hazel, staked. Hazel branches also served as boundary markers. The wisdom staff of judicial and forest sovereignty was made of hazel wood.
Hazelnuts was and is ascribed the ability to allow currents of force to flow. Therefore, hazel rods are used as a dowsing rod . The shrub is also said to protect against lightning strikes and divert disruptive earth and water jets. Hazel magic was banned in early Franconian times ( Lex Ripuaria ), but it continued to exist for centuries. Belief in the divining rod remained widespread until the 17th century. They wanted to track down treasures, metal veins and springs with it. This use is illustrated in Georgius Agricola's “ De re metallica ” from 1556. Its use as a divining rod has survived to this day. A more prosaic use of the hazel is hidden behind the phrase "refresh someone with hazel juice" : as a whipping stick . The hazel was not held in high esteem by Saint Hildegard von Bingen : the hazel tree is a symbol of lust and is hardly suitable for healing purposes . Nuts have been associated with sexuality and fertility . This sexual connotation of the hazel can be seen in the folk song:
- The nightingale does not sing on a Christmas tree,
- Beat in the hazelnut tree ...
The nightingale only sings while looking for a female, not after mating. The phrase go into the hazelnut stands for a rendezvous. The folk sayings of a lot of hazel, a lot of children without a father and who arose from a hazel bush, point to the extramarital character of such connections. The custom in many areas of placing a birch tree in front of the window for one's loved one on May 1st was modified by planting a hazel bush and the girl in question was ridiculed. From the Normandy this practice is already used from 1393. Because of this sexual symbolism hazel was used as an aphrodisiac used: to powder blown hazel bark was mixed with food or it was used hazelnut oil.
As a lucky charm and symbol of fertility, in Rome, England and Southwest Germany the bride was given a basket of hazelnuts at the wedding, or hazelnuts were thrown at the bride and groom. In ancient Rome, the bridegroom threw nuts among the guests.
The folk song Black Brown is the hazelnut is also widely used .
For the common hazel, the other German-language trivial names Augstnuss ( Swabia ), Drateln, Frau Hasel, Hagnuss ( Bern ), Hasel ( Northern Germany ), Haselbaum (Northern Germany), Haselbusch, Haselbusk ( northwest Germany ), Haselnot, Haselstude ( Middle High German) exist or existed ), Hasesnot ( Middle Low German ), Hasliboum, Haslen (Bern), Hasliholz ( St. Gallen ), Haslistuda (St. Gallen), Hassel ( Unterweser ), Hasselboum, Hasselbusch (Northern Germany), Hasselnäss ( Transylvania ), Hasselstrach (Transylvania), Hassel perennial Hasselnot, Hassel structural (Northwest Germany, low German ), Haxelnuss, Hesele (medium high German), Heselinholz (medium high German), Heslinholz (medium high German), Hesse, Hüselte, Klaeterbusk ( Bremen ), Kätzlein, Klöterbusch ( Hamburg ) March, noodles, Nööthbusch ( Mecklenburg ) , Nut blossom, nut bush and nut bush.
- Antiquity - late antiquity: Dioscurides 1st century --- Pliny 1st century --- Galen 2nd century
- Arab Middle Ages: Avicenna 11th century --- Pseudo-Serapion 13th century
- Latin Middle Ages: Hildegard von Bingen 12th century --- Konrad von Megenberg 14th century --- Herbarius Moguntinus 1484 --- Garden of Health 1485 --- Hortus sanitatis 1491 --- Hieronymus Brunschwig 1500
- Modern times: Otto Brunfels 1537 --- Leonhart Fuchs 1543 --- Hieronymus Bock 1546 --- Mattioli / Handsch / Camerarius 1586 --- Nicolas Lémery 1699/1721 --- Onomatologia medica completa 1755
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The following books were used for the Cultural Significance section:
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- Packaging information for Delta hazelnut kernels ---- * = Archived copy ( Memento of the original from March 3, 2015 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. - see also: en: Hazelnut
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- Avicenna , 11th century: Canon of Medicine . Translation and adaptation by Gerhard von Cremona , Arnaldus de Villanova and Andrea Alpago (1450–1521). Basel 1556, Volume II, Chapter 43: Avellana (digital copy )
- Pseudo-Serapion 13th century, print. Venice 1497, sheet 120r (No CLXII): Nux avellana (digitized)
- Charles Victor Daremberg and Friedrich Anton Reuss (1810–1868). S. Hildegardis Abbatissae Subtilitatum Diversarum Naturarum Creaturarum Libri Novem. Physica , Book III, Chapter 11: Hazel Tree . Migne, Paris 1855. Sp. 1225 (digitized version ) - Translation: Herbert Reier: Hildegard von Bingen Physica. Translated into German after the text edition by JP Migne, Paris 1882. Kiel 1980, p. 115: The hazel tree is more cold than warm and is not suitable for medicine; he symbolizes the opulence. But take its buds when its flowers are about to burst, dry them in the sun, pulverize them, and where there is scrofula in a person, sprinkle the powder on them, and he will be cured. A man whose seeds melt away so that he does not father a child would eat the fruits of the hazel tree, plus the third part of earth pepper and the fourth part of earth pepper, grape and some common pepper, cook it with the liver of a young deer that is sexually mature, and served with raw and fatty pork. He throws away those herbs and eats this meat, also dip bread in the water in which this meat is boiled and chew it. If he does this often, a child will blossom for him unless the righteous judgment of God prevents it. The nuts are neither useful nor harmful to a healthy person who eats them. They harm a sick person because they demphent him in the chest.
- Konrad von Megenberg , 14th century: Book of nature. Output. Franz Pfeiffer . Aue, Stuttgart 1861, p. 334 (IVa / 32): Haselnuzz (digitized version )
- Herbarius Moguntinus , Mainz 1484, Part II, Chapter 45: Avellane (digitized version)
- Gart der Gesundheit . Mainz 1485, Chapter 280: Nux avellana. Hazelnut (digitized version )
- Hortus sanitatis 1491, Mainz 1491, Part I, Chapter 313: Nux avellana (digitized version)
- Hieronymus Brunschwig : Small distilling book , Strasbourg 1500, sheet 58r: Hazel nut (digitized version )
- Otto Brunfels : Ander Teyl des Teütschen Contrafayten Kreüterbůchs . Johann Schott, Strasbourg 1537, p. 155: Hazelnut (digitized version )
- Leonhart Fuchs : New Kreütterbuch… Michael Isingrin, Basel 1543, Chapter 151: Hazelnut (digitized version )
- Hieronymus Bock : New Kreütter Bůch . Wendel Rihel, Strasbourg 1546, Part III, Chapter 67: Hazelnut (digitized version )
- Pietro Andrea Mattioli : Commentarii, in libros sex Pedacii Dioscoridis Anazarbei, de medica materia. Translation by Georg Handsch, edited by Joachim Camerarius the Younger , Johan Feyerabend, Franckfurt am Mayn 1586, sheet 98v – 99v: hazelnut (digitized version )
- Nicolas Lémery : Dictionnaire universel des drogues simples. , Paris 1699, p. 228: Corylus (digitized) ; Translation. Complete material lexicon. Initially designed in French, but now after the third edition, enlarged by a large one [...] translated into High German / by Christoph Friedrich Richtern, [...]. Leipzig: Johann Friedrich Braun, 1721, Sp. 356: Corylus (digitized version)
- Albrecht von Haller (editor): Onomatologia medica completa or Medicinisches Lexicon which clearly and completely explains all names and artificial words which are peculiar to the science of medicine and the art of pharmacy [...]. Gaumische Handlung, Ulm / Frankfurt am Main / Leipzig 1755, Sp. 487: Corylus (digitized version )
- Translation of the text by Franz Unterkircher. Tacuinum sanitatis … Graz 2004, p. 57: Hazelnuts. Lambert nuts (tree hazelnuts): Complexion: warm in the first degree. Prefer large and juicy ones. Benefit: they promote sexual potency and brain activity. Harm: they harm the stomach. Prevention of harm: with barley sugar. What they produce: sharp and not good blood. Particularly beneficial for people with cold complexion, the weak and old, in winter, in northern areas.
- Common hazel. In: FloraWeb.de.
- Common hazel . In: BiolFlor, the database of biological-ecological characteristics of the flora of Germany.
- Profile and distribution map for Bavaria . In: Botanical Information Hub of Bavaria .
- Corylus avellana L. In: Info Flora , the national data and information center for Swiss flora . Retrieved October 3, 2015.
- Distribution in the northern hemisphere according to Eric Hultén
- Thomas Meyer: Data sheet with identification key and photos at Flora-de: Flora von Deutschland (old name of the website: Flowers in Swabia )
- Brief description at baumkunde.de
- Goods information hazelnut from Transport-Informations-Services (TIS) the Gesamtverband der Deutschen Versicherungswirtschaft e. V. (GDV).
- Bochum Botanical Association V .: Differences between common hazel, Lamberthasel and tree hazel
- Corylus avellana inthe IUCN 2013 Red List of Threatened Species . Posted by: Participants of the FFI / IUCN SSC Central Asian regional tree Red Listing workshop, Bishkek, Kyrgyzstan (July 11-13, 2006), 2007. Accessed December 12, 2013.