It is a
deciduous shrub tall, with
stems up to thick. The
leaves are rounded, long by broad, with a coarsely double-serrated margin. The
flowers are
wind-pollinated catkins produced in late winter. The
male (
pollen) catkins are pale yellow, long, while the
female catkins are bright red and only long. The
fruit is a
nut produced in clusters of 1–5 together. Each nut is long, fully enclosed in a long, tubular
involucre (
husk).
Similar species The filbert is similar to the related common hazel,
C. avellana, differing in having the nut more fully enclosed by the tubular
involucre. This feature is shared by the beaked hazel
C. cornuta of North America, and the Asian beaked hazel
C. sieboldiana of eastern Asia. ==Distribution and habitat==