Linum usitatissimum aka Linseed

Linum usitatissimum is common flax, also known as linseed. It belongs to the flax family, Linaceae. Its native range runs from Türkiye to Iran. It has spread beyond gardens across Europe and parts of North America. Gardeners grow it as an annual, though NC State notes perennial growth in its native habitat. It grows at a medium rate and needs moderate upkeep.

One or more stems rise from the plant's base. These stems can stand upright or trail over the ground. They are slim and strong, with smooth, hairless surfaces. The narrow green leaves grow in an alternate pattern. Each leaf has a smooth edge and a lance-shaped outline. Leaves measure about 0.08–0.25 feet [0.025–0.076 metres] long. The sources give no clear mature height or spread.

Pale blue flowers appear from late spring through midsummer. Each flower has five broad petals that spread outward. Flowers reach about 0.08 feet [0.025 metres] across. They grow in cymes above the thin stems. Round brown capsules follow the flowers, with harvest noted in autumn. Each capsule holds ten flattened seeds within a divided chamber. The flowers suit borders, meadows, rock gardens, and cottage gardens. Gardeners can also grow flax in groups or naturalized areas.

Flax grows best in full sun with moist, well-drained soil. Humus-rich loam suits it well. PFAF gives a preferred soil pH of 5–7. NC State also reports tolerance of mildly alkaline soil. The plant withstands drought, dry ground, and strong winds. It does not suit sites exposed to sea winds. Cool, moist weather supports growth during the growing season. Dry weather can leave plants short and woody. Very light, rich soils can promote tall growth that falls over. NC State lists USDA zones 4–8, but notes poor cold tolerance. Cutworms and grasshoppers may attack the plant.

People use stem fibre to make linen, paper, nets, and insulation. Seeds supply linseed oil and serve as food in breads and cereals. They can also be sprouted for salads. Traditional remedies use seeds and oil, chiefly for their laxative effects. Food use does not mean all plant material is safe. Flax contains cyanogenic glycosides, which can release cyanide after damage. Large amounts can cause severe poisoning in people and animals. Cornell reports poisoning risks for cattle and sheep. Pet Poison Helpline also warns of danger to pets. Linseed oil can irritate skin on contact.