Crops Flax and Linseed (Linum usitatissimum)

Summary Information



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Linseed, young plants

The plant is an erect annual, forming a short taproot: flax may grow to a height of 120 cm, but varieties grown for oil production are usually considerably shorter at maturity. The stems are thin and wiry, the degree of branching depending upon plant type and density; the leaves are unstalked, small, narrow and pointed and dark or greyish-green in colour.

Linseed, plants in flower

The flowers are produced near the top of the stems, each being separately stalked: while the flowering period may last for some weeks, individual flowers are short-lived. Linseed flowers are commonly bright blue, but may be pale blue or white, while most flax cultivars bear white flowers.

Linseed, ripening capsules

Each flower is succeeded by a rounded capsule in which the seeds develop, this ripening from green to light brown. For both crops, a fine and firm but uncompacted seedbed is essential for even establishment, sowing taking place when the soil is sufficiently warm in spring.

Flax, plants in bud

Flax is sown thickly in narrow rows, to obtain a close stand of up to 2000 plants per square metre, thus minimising basal branching and so improving fibre quality; sowing rates for linseed are lower, the objective being a plant density of about 500 plants per square metre. Soil phosphate and potash status should be good for both crops, but nitrogen requirements are low; 75 kg per ha, applied to a young crop, is sufficient for linseed, while flax is frequently given no nitrogen in order to discourage sappy growth. Crops are not very competitive with weeds; some herbicides are available, as are pesticides to control fungal diseases and insect pests. Flax crops intended for best quality fibre are pulled when the lower leaves have fallen; the pulled flax is then retted (this is a controlled rotting process), and scutched (to separate the loosened fibres from the bulk of the stem tissue), yields of fibre normally being in excess of 1 t per ha. Linseed is harvested when the capsules are ripe: often combining is facilitated by preceding chemical desiccation of the stems, seed yields of 2 t per ha or more often being obtained. Current development is proceeding in several different directions. Dual purpose crops are now being grown, from which, after combining, the dry straw is mechanically processed to produce relatively short flax fibres which may be used in the manufacture of specialist papers, composite materials, and biodegradable matting products. By-products of oil extraction such as protein flours and mucilage are finding increasing application in the food, cosmetic, and pharmaceutical industries. Winter-hardy varieties of linseed, and also yellow-seeded cultivars with altered fatty-acid profiles, are being introduced to commercial cultivation; the latter are intended for edible oil production but industrial uses are also likely