Flax (also known as common flax or linseed) (binomial name: Linum usitatissimum) is a member of the genus Linum in the family Linaceae. It is native to the region extending from the eastern Mediterranean to India and was probably first domesticated in the Fertile Crescent. Flax was extensively cultivated in ancient Ethiopia and ancient Egypt.

Yet linseed is of increasing importance for the industry in highly developed consumer markets due to the specific non saturated fatty acids. In addition to referring to the plant itself, the word "flax" may refer to the unspun fibers of the flax plant.

Specifications