Corylus maxima

The filbert is in the birch or Betulaceae family and is native to southeastern Europe and southwestern Asia, from the Balkans to Ordu in Turkey. It is a deciduous shrub 6–10 m tall, with a stem up to 20 cm in diameter.

The filbert is similar to the related common hazel, C. avellana, differing in having the nut more fully enclosed by an elongated tubular involucre (husk). This feature is shared by the beaked hazel (C. cornuta) of North America.

The purple-leaved cultivar (Corylus maxima 'Purpurea') is a popular ornamental shrub in gardens. Leaves are deep red-purple in spring, turning to greenish-purple in summer.

• Leaves are alternate, simple, rounded, 5–12 cm long by 4–10 cm broad, with a coarsely double-serrated margin. The new growth is covered in sticky hairs.
• Flowers are wind-pollinated catkins produced in late winter; the male (pollen) catkins are pale yellow, 5–10 cm long, while the female catkins are bright red and only 1–3 mm long.
• Fruit is a nut produced in clusters of 1–5 together; each nut is 1.5–2.5 cm long, fully enclosed in a 3–5 cm long, tubular involucre (husk).