The hazels (Corylus) are a genus of deciduous trees and large shrubs native to the temperate northern hemisphere. The genus is usually placed in the birch family Betulaceae, though some botanists split the hazels (with the hornbeams and allied genera) into a separate family Corylaceae. They have simple, rounded leaves with double-serrate margins. The flowers are produced very early in spring before the leaves, and are monoecious, with single-sex catkins, the male pale yellow and 5–12 cm… (More on Hazel)