The common hazel (Corylus avellana) is a deciduous woody plant native to Europe, Asia and North Africa. In many English-speaking countries it is referred to as the hazelnut. It is the principal species of the genus Corylus. The common hazel is a large tree growing to 20 m (66 ft) tall, with stout stems clad in smooth, brownish bark. The leaves are deciduous, rounded, 6–12 cm (2.4–4.7 in) long and across, softly hairy on both surfaces, and with a double-serrate margin. The flowers are produced early in spring on catkins 2–5 cm (0.79–1.97 in) long, the individual flowers pendulous, with no petals, and wind-pollinated.
Hazelnuts prefer well-drained soils with a pH in the range of 5.5 to 8.0. They also prefer a soil rich in organic matter. The optimum growing temperature for hazelnuts is between 15 and 20 °C (59 and 68 °F). In commercial hazelnut production, trees are generally spaced 4 m (13 ft) apart in the row. It is wind pollinated.
Specie: Corylus avellana
Common Names: Leska
Family: Betulaceae
Sub Family: Coryloideae