- Name also: Common Hazel, Cob-nut
- Family: Birch Family – Betulaceae
- Growing form and height: Shrub with several erect trunks. 2–5 m (6.5–16 ft.).
- Flower: Small, lacking perianth. Male and female flowers in separate inflorescences. Male flowers yellow, borne in a pendent catkin. Bud-like female inflorescence erect. Stigmas thread-like, deep red. Wind-pollinated.
- Leaves: Alternate. Obovate (broadest near the tip), base cordate (heart-like), apex acuminate (with a short, slender tip), hairy, soft. Margins doubly serrate.
- Buds: Egg-shaped–round, blunt at top. On shadowy side green and red, on sunny side reddish-brown.
- Fruit: Fairly large nut enclosed in an incised, bell-shaped husk.
- Habitat: Dryish broadleaf woods, especially on slopes. Favours calcareous sites (is a calciphile).
- Flowering time: Mars–April. Flowers before coming into leaf.
Hazel is a southern species of warm, sheltered wooded hillsides. It flowers before coming into leaf in spring. One individual usually has 10 to 20 main stems which regenerate efficiently through suckering. Northern distribution is limited by frost, especially spring frosts. As a light-demanding species hazel benefits from human activities, e.g. forest cuttings and cattle grazing. Over-growing by spruce is the most severe threat to a hazel grove.
Hazelnuts were formerly economically important and they were commonly gathered. Also wood mice, squirrels, and jays like to eat the nuts. Where hazel is common, ‘vihtas’ (bath whisks used in the sauna) have been made from its soft-leaved twigs.