Flax have been domesticated just once from the wild species "Linum bienne", called pale flax. Several other species in the genus "Linum" are similar in appearance to "L. usitatissimum", cultivated flax, including some that have similar blue flowers, and others with white, yellow, or red flowers. Some of these are perennial plants, unlike "L. usitatissimum", which is an annual plant. Cultivated flax plants grow to tall, with slender stems. The leaves are glaucous green, slender lanceolate, 20–40 mm long, and 3 mm broad. The flowers are pure pale blue, 15–25 mm in diameter, with five petals. The fruit is a round,
Flax not be useful, and the fiber will be underdeveloped. The fiber degrades once the plants turn brown. Flax grown for seed is allowed to mature until the seed capsules are yellow and just starting to split; it is then harvested in various ways. A combine harvester may either cut only the heads of the plants, or the whole plant. These are then dried to extract the seed. The amount of weeds in the straw affects its marketability, and this, coupled with market prices, determines whether the farmer chooses to harvest the flax straw. If the flax straw is not harvested,