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Linum usitatissimum L.

Linaceae
Flax

Source: James A. Duke. 1983. Handbook of Energy Crops. unpublished.


  1. Uses
  2. Folk Medicine
  3. Chemistry
  4. Description
  5. Germplasm
  6. Distribution
  7. Ecology
  8. Cultivation
  9. Harvesting
  10. Yields and Economics
  11. Energy
  12. Biotic Factors
  13. References

Uses

Flax is cultivated for its fiber and oil. Linen is the most important product made from the fiber of the flax plant. Flax is soft, lustrous and flexible, although not so flexible or elastic as cotton or wool. It is stronger than cotton, rayon or wool, but weaker than ramie. Special skill is needed for spinning fine linen yarns and for weaving these yarns into fine linen fabrics. This work is done in limited areas of Ireland, Scotland, N. France, and Belgium, where a high degree of skill has been developed by many generations of workers. Lower quality fiber is used in manufacturing of towelling, matting, rugs, twines, canvas, bags, and for quality papers, as for printing currency notes. Seeds contain 20–30% protein, and are the source of linseed oil, a drying oil, one of the oldest to have been used commerically. Paint and varnish industries consume about four-fifths of the linseed oil produced. It is also used in enamels, linoleum, oilcloth, and patent leather, and as waterproofing for raincoats, slickers, and tarpaulins. In some countries it is used as edible oil, and in soap manufacture. Linseed oil is also used in printers ink, for making sand forms for metal casting, and as spray on concrete roads to prevent ice and snow from sticking; linseed oil also preserves the concrete and prevents surface cracking and wear. Linseed cake or linseed meal is the flaxseed with most of the oil pressed out; 3–6% of oil remains in the cake. It is used as feed for livestock and is prized for its high protein content. Cake is prepared for feeding by grinding to linseed meal or by making pellets suitable for feeding in outdoor feed lots or on the range. Flax straw from seed flax varieties is used in the manufacture of upholstery tow, insulating material, rugs, twine, and paper. Some of the better quality straw, produced in the more humid sections or under irrigation, is used in manufacture of cigarette and other high-grade papers. Flax straw is rarely fed to livestock. If mature and of good quality, it is about equal to oat or barley straw in feed value. It can be used safely as the only roughage for cattle. The fibers are digested like other fibrous materials and do not accumulate in the stomach to form indigestible balls.

Folk Medicine

Considered anodyne, astringent, cyanogenctic, demulcent, diuretic, emollient, expectorant, laxative, suppurative and vulnerary, Linum finds its way into folk remedies for boils, bronchitis, burns, cancer, carbuncles, cold, conjunctivitis, corns, coughs, diarrhea, gonorrhea, gout, inflammation, intoxication, labor, rheumatism, scalds, sclerosis, sores, spasms, swellings, tumor. Since linen has a long anticancer folk history, it is interesting to see that Linum contains the anticancer agents 3'-demethylpodophyllotoxin, podophyllotoxin and b-sitosterol. Seeds are considered emollient, demulcent, pectoral, diuretic, and astringent. Crushed seeds make a good poultice, either alone or with mustard; lobelia seed added in the poultice for boils. Sometimes seed are roasted and used in a poultice. Sometimes employed as an addition to cough medicines. Linseed tea used for colds, coughs, irritation of the urinary tract (when honey and lemon juice may be added). Internally, oil given as a laxative. Linseed oil mixed with an equal quantity of lime water, known as carron oil, is applied to burns and scalds. Oil mixed with honey is used as a cosmetic for removing spots from the face. In veterinary medicine, oil is used as a purgative for sheep and horses, and a jelly formed by boiling seeds is often given to calves. Hartwell notes that flax is a folk remedy for such cancerous conditions as apostemes, cancer of the breast, and mouth; condylomata, indurations of the breast, cervix, limbs, liver, spleen, stomach, testicles, uterus, and viscera; sycosis; tumors of the abdomen, fauces, feet, glands, intestines, neck, parotids, testicles, uterus, and uvula; warts, and whitlows.

Chemistry

Per 100 g, the seed contains 498 calories, 6.3–6.6% H2O, 18.0–20.3% protein, 34.0–37.1% fat, 33.6–37.2 total carbohydrate, 4.8–8.8% fiber, 2.4–4.5% ash, 170–271 mg Ca, 370–462 mg P, 2.7–43.8 mg Fe, 0–30 mg b-carotene equivalent, 0.17 mg thiamine, 0.16 mg riboflavin, and 1.4 mg niacin. The hay (ZMB) contains 7.8% protein, 3.3% fat, 81.7% total carbohydrate, 46.2% fiber, 7.2% ash, 0.72% ca, and 0.11% P. Crude linseed oil contains 0.25% phosphatides, the component fatty acids being 11% palmitic, 11% stearic, 4% hexadecenoic, 34% oleic, 20% linoleic, 171 linolenic, and 3% unsaturated C20–22. There is some wax in the crude oil containing 18.7% stearic acid, 32.5% cerotic acid, 43.1% ceryl alcohol, and 7.0% hydrocarbons. The essential amino acids are (g/16 g N) 8.4 g arginine, 1.5 histiding, 2.5 lysine, 1.5 tryptophan, 5.6 phenylalanine, 2.3 methionine, 5.1 threonine, 7.0 leucine, 4.0 isoleucine, and 7.0 valine. The ash of linseed contains 30.6% K2O, 2.1% Na2O, 8.1% CaO, 14.3% MgO, 1.1% Fe2O3, 41.5% P2O5, 2.3% SO3, 0.2% Cl, and 1.2% Si. The tough hulls of linseed contain 7.9% moisture, 3.2% N, 1.8% oil, and 3.0% ash. The cake (97% DM) contains 30.5% protein, 6.6% fat, 43.2% NFE, 9.5% CF, and 7.0% ash, with per 100 g 0.57 mg thiamine, 0.33 riboflavin, 4.1 thiamine, 1.2 mg pantothenic acid, plus a little Vit. E. Lacking Vit. A, C, and D, the cake contains 0.37% Ca, 0.86% P, 1.24% K, 0.11% Na, 0.04% Cl, 0.38% S, 0.58% Mg, 0.017% Fe, and 3.95 mg/100 g Mn and 2.65 mg/100 g Cu (CSIR, 1948–1976). Seeds also contain 15% mucilage, along with wax, resin, sugar, Phosphates, acetic acid, and a small quantity of HCN-glucoside, linamarin. Flowers with immature seeds contain 0.69% HCN; 0.22 kg (half pound) of flowers will cause death of bullocks.

Description

Erect glabrous annual herb; stems 7.5–12 dm tall, corymbose-branched above, terete, grayish-green; leaves gray-green, alternate, linear-lanceolate, numerous, flat, 2–3.5 cm long, 2–4 broad, acute to acuminate, gradually and slightly narrowed at base, glaucous; flowers borne in loose, terminal, leafy racemes or open cymes, on long erect pedicels, 2–4 cm long; sepals five, long-acuminate, ovate-oblong, 5–7 mm long, entire, eglandular, 3-nerved, margins serrulate, about half as long as the petals; petals blue, or white or pale pink, 1 cm or more long, obovate; stigmas linear, decurrent along the inner side of styles; fruit a 5-celled capsule, on long erect pedicels, globose-ovoid, 7–10 mm high, about 7 mm across, surrounded by the persistent calyx, indehiscent; seeds up to 10 per capsule, yellow or light brown to dark brown, shining, varying in size, weighing from 3–12 gm per 1,000 seeds, flat, oval, one end rounded, the other pointed. Fl. June–Sept. in United States; June–August in Japan (Reed, 1976).

Germplasm

Reported from the Central Asian, Near Eastern and Mediterranean Centers of Diversity, flax or cvs thereof is reported to tolerate disease, drought, fungi, grazing, herbicides, hydrogen fluoride, high pH, pesticides, rust, virus, and weeds (Duke, 1978). Over 300 flax cultivars are known in the world. In any area, they should be selected for the best over-all performance in the growers locality and purpose, (fiber, seed, or both). For fiber production, long-stemmed varieties that are sparsely branched are best. For seed production, shorter, branching varieties should be selected. For fiber-seed production, a combination of these factors are necessary. Those grown in Oregon are: 'Cascade', 'J.W.S.', and 'Cirrus'. Nearly all cvs now grown commerically in the United States belong to the wilt-resistant, short-fiber type. In India, 'Himalini-I' yielded 910 kg linseed compared to 534 for the standard cv 'LC 185'. (2n = 30)

Distribution

Native to Central Asia and Mediterranean Region. Remains of flax plants have been found in refuse of stone age dwellings in that region. Cultivated in Mesopotamia, Assyria and Egypt for over 5,000 years; now cultivated in many countries around the world.

Ecology

Requires a cool temperate or subtropical region where the temperature is favorable for production of spring-sown small grains. Seed flax is raised under a fairly wide range of conditions, but fiber flax requires abundant moisture and cool weather during the growing season, and warm dry weather during harvesting of seed and fiber, especially where water-retting is practiced. In some areas dew-retting is practiced. Relative humidity at noon should be about 60–70%. Crop requires 15–20 cm of rainfall if spread evenly over growing season, with 2.5 cm falling just before or after planting. Needs a relatively long ripening period between flowering and harvesting. Warm, dry weather desirable at heading stage to cause plants to branch and produce seed; after vegetative growth, dry weather required for curing the seed. Needs abundant moisture; dry conditions make plants short and woody. Waterlogging detrimental. Regions with heavy storm or wind incidence are unsuitable. More sensitive to salt than most field crops. Well-drained, loamy soils overlying a clay subsoil are best, with pH 5–7. Very light highly fertile soils not desirable as they produce tall rank growth tending to lodge. Flax is reportedly grown in Boreal Moist to Wet through Tropical Very Dry Forest life zones, where pH ranges from 4.8–8.2 (mean of 66 cases = 6.6), annual precipitation from 3–13 dm (mean of 76 cases = 7.1), and annual mean temperature from 6 to 27°C (mean of 76 cases = 12.0). Lolium and Phleum have allelopathic effects on Linum, reducing its carbohydrate synthesis (Fabian et al., 1976).

Cultivation

Propagation is usually by seed. Flax may also be propagated vegetatively from stem cuttings. Seed is recovered from fiber crop. Plump and disease-free (resistant to flax wilt) seed should be selected. All dirt, chaff, and shrunken seeds must be removed as they may carry disease. Chemicals may be used to treat the seed before planting. Sow seed 15–20 days before the last average killing frost data of the area, which is the same date as for sowing spring wheat. In Minnesota and North Dakota, flax seed sown in April or early May yields best. In Texas, flax is fall-sown in November or early December, and fits well into rotations with cotton, sudangrass, grain sorghum or vegetables. Rate of sowing seed varies from 3 kg/ha for seed production to 160 kg/ha for fiber production. Seed sown in rows 11.5 to 75 cm apart in various countries, depending on whether plant is grown for fiber (closer) or seed (each plant given more room). In some sections flax and spring wheat are seeded together and the resulting threshed crop separated by screening with a fanning mill. Yields are increased and weeds are better controlled by seeding with a mixture of 2 or 3 pecks of wheat seed with 28–45 kg of flaxseed per hectare. Flax germinates at a lower temperature than many of the grassy weeds that may become troublesome later. A well-prepared firm seedbed will ensure sowing at the proper depth and this will result in prompt and uniform germination. Flax should be sown at depth of 2.5–3.2 cm with a grain drill rather than with a broadcast-seeder. However, in some countries, seed is broadcast and harrowed in. Fall plowing flax fields is preferable as it allows soil to settle. Soil should be packed by rolling, disking, harrowing and surface leveled before planting. In Texas fall-sown flax is used to eradicate Johnsongrass from fields as the flax grows while the Johnsongrass is dormant and takes over the area so the Johnsongrass cannot get a foothold. Flax responds well to irrigation, especially light irrigations as it is a shallow-rooted crop. When crop begins to ripen, irrigation should be withheld to hasten maturity. If soil is kept wet, blooming,may continue indefinitely. Total water applied usually 9,000–12,000 cu m/ha; 1–10 irrigations may be necessary per season. Very little added N is needed, only 20 kg/ha, except in irrigated California crops where need for all fertilizers in higher. Compared with other crops, flax requires relatively small amounts of nutrients. In other countries, such as Sweden, a complete NPK fertilizer is used, 300–400 kg/ha; in The Netherlands, 20–40 kg/ha of N used, and P and K added as required. Heavy manuring can produce heavy yields, but there is an accompanying fall in the quality of the fiber. The aim in fertilizing is to improve the yield without causing corresponding fall in quality. Direct organic manuring should be avoided when fiber flax is grown on well-cultivated soils that are amply supplied with nutrients. Organic manures, such as farmyard manure, are best applied to the preceding crop. Microelements may be needed on a particular soil, and should be added after a soil test. Various rotation plans are followed in different countries in which 6–11 years intervene between flax plantings on a given piece of land.

Harvesting

Most flax cvs mature in 90–120 days, but some winter-planted cvs require more than 200. Flax seed may be harvested in the same manner as wheat. Probably two-thirds of the crop is combined, and may be harvested with a grain binder, with a swather (windrower) or by direct combining which is the cheapest method and is entirely satisfactory, when the flax is thoroughly dry and free of weeds. Care in threshing necessary to prevent cracking of seed for propagation. Maturity of flax is judged by the color of the bolls (seed capsules) rather than by the color of the straw. Crop ripe enough to harvest when 90% of bolls have turned brown, although crop can be pulled at beginning of seed ripening, since immature seed bolls mature after harvest and produce viable seed. Static electricity is sometimes a problem in harvesting, and may occur at high temperatures (38°C) and low humidities. Seeds cling together and to combine; screens may get clogged and serious seed loss can result. Harvest must be delayed until humidity increases slightly or temperature is low enough to prevent it. For storage, seed must have a low moisture content, 8–10%. When crop is grown for the fiber, it is harvested with a special pulling machine or may be pulled by hand as is done in Europe; machines are still not entirely satisfactory. The pulled flax is shocked in the field until dry, when the seed is threshed in such a way as to prevent the breaking of the straw. Stems are harvested when the lower two-thirds of stem have turned yellow and the leaves have fallen from it, about 1 month after the appearance of first flowers. Straw is then retted, by bacterial fermentation, to remove gums and resins from the fiber. Retting may be simple exposure of the straw to the weather for 2–3 weeks, depending, on weather; it may take up to 8 weeks, or until the dew and rains have removed the resins and the fiber is loosened, or more complicated methods of soaking in water for about a week under specific regulation of time and temperature. It can also be done chemically, but these methods cost more. When straw has been properly retted, it is dried, broken and scutched to separate the fiber from the bark and stems, after which it is baled and is then ready to be manufactured. Fibers are about 50 cm long average, but may vary from up to 1 m. Flax fibers are in the cambium layers of the plant, and are bast or phloem fibers. They occur in bundles in the pericycle; each bundle containing about 10–40 individual fibers. Each stem contains about 30 fiber bundles forming a ring around the stem. Retted flax contains about 64% cellulose, 17% hemicellulose and 2% lignin. Before straw is retted, seed capsules are removed, (called "rippling"), usually by machine. One ton of fiber flax yields 100 kg of seed. It is possible to extract fiber from flax straw without retting, (called "green flax"). After straw is deseeded, it is taken directly to the breaker and the scutcher. This fiber has a considerable amount of extraneous matter attached, making it necessary to degum before spinning the fiber. This method usually results in a higher production of short tow fiber than there is with retted flax fiber.

Yields and Economics

Fiber yields run 200–1200 kg/ha. Seed production figures underate seed yields of 220 to 2820 kg/ha, but locally yields can be much higher. Record seed yields in the U.S. range from 2460 kg/ha in the northern States to 4390 kg/ha for winter sowings in Arizona/California (Dybing and Lay, 1981). According to Agricultural Statistics 1981, yields of flaxseed per harvested acre range between 7.9–13.7 bushels per acre (roughly 25.4 kg/bushel) with the average farmers price of $2.38 to $9.67 per bushel. Production figures for most countries fall under 1 MT/acre = 2.5 MT/ha, but in 1980 Mexico, Uruguay, and Egypt exceeded this. Flax straw average yields range from 5–7 MT/ha. As indicated by the use of flax for fiber and linseed oil, this crop is and has been for a long time, a very important crop in the economics of many nations. It is grown in many countries as an important crop. In the United States it is grown in the North Central States and in the Imperial Valley of California. For flax seed, the main producers are Argentina, United States, Canada, USSR, India, and Uruguay; for flax fiber, USSR (65–70% of world production), France, Poland, Belgium, The Netherlands. The major consumers are United Kingdom (imported 37,000 tons of flax fiber and tow in 1968), West Germany, Italy, France, and Belgium. Present world production 725 thousand MT fiber grown on 1,729,000 ha.

Energy

With seed yields of 1000–4000 kg/ha quite feasible, and reported oil content of 34–37%, we can see oil yields of 1500 kg/ha with slight agronomic improvements. At VODF Seminar II, it was concluded that linseed oil has caused so many problems in engine tests as to be totally rejected by several investigators as a candidate fuel oil.

Biotic Factors

When grown for seed, flax is self-pollinating. Cross-pollination does not seem to increase seed yield consistently. Advisable to isolate different varieties by at least 100–300 m when producing seed for propagation. Many fungi have been found on flax, but the most serious diseases are flax wilt, several rusts, seedling blights, and Pasmo. Causative agents are: Alternaria brassiceae, A. lini, A. linicola, A. solani, A. tenuis; Ascochyta linicola, Botrytis cinerea, Colletotrichum lini, C. linicola, Corticium solani, Diplodia lini, Erysiphe cichoracearum, E. polygoni, E. polyphaga, Fusarium acuminatum, F. avenaceum, F. lini, Kabatiella lini, Leveillula linacearum, Melampsora lini, Mycosphaerella linorum, M. tulasnei, Oidiopsis lini, Oidium lini, Phoma lini, P. linicola, Polyspora lini, Pythium spp., Rhizoctonia solani, Sclerotinia fuckeliana, S. libertiana, S. minor, S. sclerotiorum, Sclerotium rolfsii, Septoria linicola, Sphaerella linorum, Thielaviopsis basicola and Trichothecium roseum. Important viruses causing disease in flax are: Aster yellows (Chlorogenus callistephi), Beet curly top and Yellows. Flax may be parasitized by Cuscuta epilinum, C. epithymum, C. indecora, C. pentagona and Striga lutea. The bacteria Agrobacterium tumefaciens and Pseudomonas atrofaciens also cause diseases. Insects are not a serious problem in flax production. Nematodes isolated from flax include the following species: Ditylenchus dipsaci, Helicotylenchus erythrinae, H. spp., Heterodera schachtii, Meloidogyne arenaria, M. hapla, M. incognita., M. incognita acrita, M. thamesi, M. javanica, Paratylenchus sp., Pratylenchus coffeae, P. penetrans, Tylenochorhynchus spp., and Xiphinema spp.

References

Complete list of references for Duke, Handbook of Energy Crops
Last update Wednesday, January 7, 1998 by aw