Hazelnut oil is obtained by first cold pressing the fruit of the botanical species Corylus avellana L. belonging to the Betatulaceae family.
It is a tree that normally reaches between 3 and 8 m in height, although at times it can reach 15 m with a very extended crown of irregular shape, generally branched from the base. With pale brown or gray bark and deeply striated, its wood is hard, flexible and very resistant. The rounded leaves are between 6 and 12 cm long and wide and are smoothly pubescent on both sides, with doubly serrated edges.
The flowers are born before the leaves, in early spring. They are monoecious and with catkins of differentiated sex; the male ones pale yellow in color and between 5 and 12 cm long, the female ones very small and practically hidden in the buds from which the bright red styles emerge, in number from 1 to 3.
The fruit is the hazelnut, which is produced in groups of 1 to 5, each one contained in a small and leafy involucre that encloses about 3/4 of the nut. The maturation takes 7 to 8 months and then the envelope opens releasing the hazelnut.