Hazelnut trees, scientifically known as Corylus avellana, are deciduous trees or large shrubs that produce edible nuts called hazelnuts. They typically grow to a height of 10 to 20 feet and thrive in temperate climates. These trees prefer well-drained soil and can often be found in woodlands or cultivated orchards. The hazelnut tree has distinctive round leaves with serrated edges and produces small, yellow catkins in early spring. The nuts mature in late summer to early fall, encased in a hard shell and surrounded by a leafy husk. Hazelnuts are popular for their rich flavor and are commonly used in various culinary dishes, including desserts and spreads like Nutella.