Technically, linen is a vegetable. Linen fabric is made from the cellulose fibers that grow inside of the stalks of the flax plant, or Linum usitatissimum, one of the oldest cultivated plants in human history.

Flax is an annual plant, which means it only lives for one growing season. From seed-planting, it is ready to be harvested in about a hundred days. Unless the weather is particularly warm and dry, flax requires little watering or attention during this time. It grows to about three or four feet tall, with glossy bluish-green leaves and pale blue flowers, though on rare occasions, the flowers bloom red.

Flax is cultivated around the world not only for its fine, strong fibers, but also for its seeds, which are rich in nutrients such as dietary fiber and omega-3 fatty acids. Flax oil is also a popular drying oil among oil painters.

Flax fibers vary in length from about 25 to 150 mm (1 to 6 in) and average 12-16 micrometers in diameter. There are two varieties: shorter tow fibers used for coarser fabrics and longer line fibers used for finer fabrics. Flax fibers can usually be identified by their “nodes” which add to the flexibility and texture of the fabric.

The cross-section of the linen fiber is made up of irregular polygonal shapes which contribute to the coarse texture of the fabric.

The quality of the finished linen product is often dependent upon growing conditions and harvesting techniques. To generate the longest possible fibers, flax is either hand-harvested by pulling up the entire plant or stalks are cut very close to the root. After harvesting, the plants are dried, and the seeds are removed through a mechanized process called “rippling” (threshing) and winnowing.

The fibers must then be loosened from the stalk. This is achieved through retting. This is a process which uses bacteria to decompose the pectin that binds the fibers together. Natural retting methods take place in tanks and pools, or directly in the fields. There are also chemical retting methods; these are faster, but are typically more harmful to the environment and to the fibers themselves.

After retting, the stalks are ready for scutching, which takes place between August and December. Scutching removes the woody portion of the stalks by crushing them between two metal rollers, so that the parts of the stalk can be separated. The fibers are removed and the other parts such as linseed, shive, and tow are set aside for other uses. Next the fibers are heckled: the short fibers are separated with heckling combs by 'combing' them away, to leave behind only the long, soft flax fibers.

After the fibers have been separated and processed, they are typically spun into yarns and woven or knit into linen textiles. These textiles can then be bleached, dyed, printed on, or finished with a number of treatments or coatings.

An alternate production method is known as “cottonizing” which is quicker and requires less equipment. The flax stalks are processed using traditional cotton machinery; however, the finished fibers often lose the characteristic linen look.

Flax is grown in many parts of the world, but top quality flax is primarily grown in Western European countries and Ukraine. In very recent years bulk linen production has moved to Eastern Europe and China, but high quality fabrics are still confined to niche producers in Ireland, Italy and Belgium, and also in countries including Poland, Austria, France, Germany, Sweden, Denmark, Lithuania, Latvia, the Netherlands, Spain, Switzerland, Britain and Kochi in India.