enclosed in a 3–5 cm long, tubular involucre (husk).

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.

Uses
The Filbert nut is edible, and is very similar to the Common Hazel nut. Filberts are sometimes grown in orchards for the nuts, but much less often than the Common Hazel.

The purple-leaved cultivar Corylus maxima 'Purpurea' is a popular ornamental shrub in gardens.

Language
The word 'filbert' is used regionally in Oregon to refer to hazelnuts in general. Use in this manner has faded partly due to the efforts of Oregon's hazelnut growers to brand their product to better appeal to global markets and avoid confusion.