Hazel trees are found throughout most of Europe, including Scandinavia and the United Kingdom, east into Russia's Ural mountain range and south to Greece and Italy. They can also be found in the Caucasus region, Iran, Morocco and Turkey. Hazel belongs to the birch tree family, Betulaceae. Its genus is Corylus, which encompasses roughly 15 species. Hazel trees can reach up to 70 years old, and more if it is pruned, either through natural damage or when trimmed by humans.
Hazel trees are deciduous and have shiny, smooth bark that's a brownish-silver colour. Lichens and mosses often cover its trunks. Hazel turns yellow in autumn. They are thick and multi-stemmed. They form the lower tier of vegetation in the forest, beneath the taller trees. Some consider hazel more like a bush than a tree because of its multiple trunks that branch out from the ground. Its leaves are round and have a rough texture because they are serrated and covered with tiny hairs. Hazel's male flowers appear as light yellow furry clusters in February. The female flowers, tiny red tufts, become nuts once fertilised by pollen carried on the wind.
The tree is mentioned in Celtic myths for its alleged powers when its hazelnuts are eaten or used in potent brews. Early Irish literature often refers to the drinking of "hazelmead," and Scottish tales describe Druids eating hazelnuts to develop prophetic powers. The association of wisdom with hazel is also found in ancient Norse mythology and Roman and Greek lore. In Scandinavia, hazel was for centuries used as a protection against evil in the form of shields, fences or when woven into caps.
Hazel includes up to 15 different species, which has led to it being known by several different names: hazel, hazelnut, filbert or cobnut. Those names were used according to the length and size of the nut, which led to confusion. Hazel was previously considered the standard name for the genus, but today in the U.S., filbert is the usual name used. Cobnut is only used for one species' commercial variety.
These trees are not bothered by many insects, but they can draw several species of moths, which lay their larvae on the hazel leaves. Some flies and a few beetles, including weevils, feed on the tree. The nuts, however, do draw some insects, especially in those found in Europe.
Hazel trees produce their edible nuts and serve as a host for a number of lichens in the United Kingdom, including some endangered or rare varieties. Lichens that grow on smooth-barked trees, or Graphidion lichens, do well on hazel trees. The Graphis alboscripta lichen grows almost exclusively on hazel and is only found in Scotland.