Corylus maxima, the filbert, is a species of hazel native to southeastern Europe and southwestern Asia, from the Balkans to Ordu in Turkey.It is a deciduous shrub 6–10 m (20–33 ft) tall, with stems up to 20 cm (8 in) thick. The leaves are rounded, 5–12 cm long by 4–10 cm broad, with a coarsely double-serrated margin.