Boehmeria nivea (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Vegetable
Medicinal
Forage / feed
Fibre
Food security

Boehmeria nivea (L.) Gaudich.

Protologue: Voy. Uranie, Bot.: 499 (1830).

Family: Urticaceae

Chromosome number: 2n = 24, 28, 42, 56

• Boehmeria tenacissima Gaudich. (1830).

• Ramie, rhea, China grass (En).
• Ramie, ramie de Chine (Fr).
• Rami, urtiga branca (Po).

Ramie probably originated in western and central China and has been cultivated in China since antiquity. Cultivation spread from China to other Asian countries. Ramie plants and products were brought to Europe in the 18^th Century and experimental plantings were established in many tropical, subtropical and temperate countries. With the advent of synthetic fibres, however, the cultivation of ramie plummeted, though it is still grown in many tropical and subtropical countries. In tropical Africa small-scale cultivation has taken place in Sierra Leone, Cameroon, Equatorial Guinea, Gabon, DR Congo, Kenya, Uganda, Tanzania, Mozambique, Madagascar and the Mascarene Islands but it has not become successful and its present distribution in tropical Africa is unclear. Ramie has occasionally escaped from cultivation and naturalised.

Fibre from the stem of ramie is one of the oldest textile fibres, used since prehistoric times, especially in China, India and Indonesia. In China it has also been used for paper making for many centuries. The fibre can be spun and the cloth (‘grass cloth’, ‘grass linen’ or ‘Chinese linen’) is used for clothing, tablecloths, napkins, sheets, pillow cases, towels, handkerchiefs, mats, sails, etc. Ramie fibre is processed into a range of other products, including canvas, mosquito nets, fire-hoses, upholstery, filter cloths, gas mantles, shoe laces, marine packings and carpet backing. Ramie is often blended with polyester, wool, silk or cotton. In Brazil undegummed ramie serves as a substitute for jute, for instance in the production of sacks. Residues remaining after fibre extraction, and also the short fibres, are used for the production of high-quality paper, such as banknotes and cigarette paper. Processing waste is also blended with cotton or rayon and made into lower-grade fabrics. Ramie fibre serves locally for the production of ropes, strings, fishing lines and nets, sewing thread and fabrics.

Ramie plants may be fed to cattle, sheep, goats, pigs, rabbits and chickens. The main parts used as fodder are the leaves and stem tops. Ramie may also be grown specifically for forage, in which case it is harvested before the fibres have fully developed. It can be given fresh, dried as a hay, ensiled with molasses or as a dried meal. The leaves and tops are also applied as green manure. In Vietnam ramie leaves are utilized in the preparation of a cake which is considered a delicacy.

In traditional medicine in DR Congo the whole plant is crushed and soaked in water to obtain a maceration which is rubbed on the body for the treatment of rheumatism, leprosy, skin diseases and wounds, instilled into the eyes to treat eye affections, instilled into the nose against rhinitis, and drunk for the treatment of diarrhoea and helminthiasis. In Malaysia ramie leaves are used to poultice boils and against flatulence; a decoction of roots and leaves is taken as a tonic in the case of dysentery and the root is applied on ulcers. In Indo-China the roots and leaves are considered to be cooling, diuretic, emollient and resolvent, and are prescribed in a number of disorders including dysuria, urogenital inflammation and prolapse of the uterus. In China and Taiwan the plant is used for diuretic, antipyretic and hepatoprotective purposes.

According to FAO estimates the world ramie fibre production in the period 2004–2008 was about 277,000 t per year, cultivated on about 132,000 ha, with more than 98% produced in China (272,000 t from 129,000 ha). In this period Laos produced 2100 t per year, the Philippines 1600 t and Brazil 1100 t. Most of the ramie produced is used in the producing countries and only a small proportion enters international trade (on average about 1100 t per year for the period 2004–2008). The main exporters in this period were China (about 900 t per year), the Philippines (70 t/year) and Indonesia (50 t/year). The major importer is Japan (800 t per year in 2004–2008). The highest quality ramie available on the world market is produced in the Philippines, mainly because of the superior processing equipment employed. Small quantities of undegummed ribbon were exported from Kenya to the United Kingdom just after the Second World War.

The ramie fibre strands of commerce are single cells (5–)40–250(–620) mm long and (10–)25–60(–126) μm wide. They are flattened in cross-section, irregular in shape, have thick walls and a well-defined lumen, and taper to rounded ends. The fibre walls show pronounced longitudinal striations. The fibre contains 69–91% α-cellulose, 5–13% hemicelluloses, 1% lignin, 2% pectin and 2–4% ash. Fibres extracted from ramie stems by decortication contain a high amount of gums, so special methods must be used to separate them. The gums are mainly composed of hemicelluloses and pectin, which are relatively insoluble in water but fairly soluble in alkaline solutions. Properly degummed fibre contains 96–98% α-cellulose.

Ramie fibre is white, lustrous, strong and durable. The tensile strength, absorbency, drying properties and dyeing qualities of ramie fibre are often indicated as superior to those of cotton and flax fibre, but measured values vary widely and with respect to these characteristics ramie is rather similar to cotton and flax. However, wetting does cause less shrinkage in ramie than in other fibres, and a mixture of wool and ramie shrinks much less than pure wool. On the other hand ramie lacks the elasticity of wool and silk and the flexibility of cotton, which makes ramie cloth rather harsh, with a tendency to crease and to crack and break when bent. The tensile strength, elongation at break, and Young’s modulus of ramie fibre are 400–1270 N/mm², 3.6–4.2% and 23,000–128,000 N/mm², respectively. Its resistance to bacterial action and its increased strength when wetted make ramie fibre particularly suitable for marine applications.

The nutritional value of ramie as fodder is high. Per 100 g dry matter the whole aboveground plant contains: crude protein 11–28 g, crude fibre 9–29 g, ash 15–17 g, Ca 3.7–4.5 g and P 0.13–0.31 g. The leaves contain about 25 g protein per 100 g dry matter, whereas total plant residues after fibre extraction contain about 13 g. Meal made of ramie leaves and tops contains 21–22% crude protein.

Aqueous root extracts showed in-vivo hepatoprotective and anti-inflammatory activity in rats, in-vitro anti-oxidant effects in rat liver homogenate, and free radical scavenging activity. Ethanol root extracts showed in-vitro and in-vivo activity against hepatitis B virus. Methanol root extracts showed in-vivo antidiabetic, antihyperlipidaemic and antioxidant effects in rats. An aqueous leaf extract showed antimicrobial properties against the fungus Acremonium kiliense and the bacteria Bacillus cereus and Bacillus subtilis, but was not effective against the fungi Alternaria brassicicola, Fusarium udum, Macrophomina phaseolina and Phytophthora parasitica. Ethylacetate leaf extracts showed free radical scavenging activity, inhibitory effects on angiotensin I-converting enzyme, and in-vitro anticancer activity.

Because of its high price ramie may be adulterated with other fibres, e.g. flax (Linum usitatissimum L.) or cotton (Gossypium spp.).

Monoecious, perennial, erect herb or small shrub 0.5–2(–3) m tall, with long rhizome and tuberous storage roots; stem usually unbranched and hollow, 8–16 mm in diameter, initially green and hairy, turning brownish and woody. Leaves alternate, simple; stipules intrapetiolar, connate at base, linear-lanceolate, up to 1.5 cm long; petiole 2.5–12 cm long, pubescent; blade broadly ovate, triangular to suborbicular, 5–20 cm × 3.5–18 cm, base cuneate to subcordate, apex usually abruptly long-acuminate, margin coarsely dentate to dentate-serrate or crenate, upper surface green and scabrid, lower surface glabrous and green or white appressed-pubescent, basal veins 3. Inflorescence axillary, racemose, paniculate, 3–8 cm long, each branch bearing several crowded or well-separated flower clusters, mainly female with a few male branches towards base; male clusters small, usually with 3–10 flowers, female clusters larger, usually with 10–30 flowers. Flowers unisexual; male flower shortly pedicelled, perianth 3–5-lobed, stamens as many as lobes and incurved with persistent rudiment of pistillode; female flower sessile, perianth tubular, 2–4-lobed, greenish to pinkish, pistil with 1-celled ovary with 1 ovule, style exserted, slender and hairy on one side, stigma filiform. Fruit a subglobose to ovoid achene c. 1 mm in diameter, enclosed by the persistent perianth, hairy, crustaceous, brown-yellow. Seed subglobose to ovoid, slightly less than 1 mm in diameter, dark brown.

Boehmeria comprises about 65 species, distributed mainly in tropical and subtropical regions, rarely in temperate regions. Considerable variation exists within Boehmeria nivea and usually two varieties are distinguished, although these have also been described as different species, subspecies or forms:

– var. nivea (‘White ramie’, ‘Chinese ramie’ or ‘China grass’) originates from China and Japan, and is characterized by a thick, white felt of hairs on the lower surface of the leaves. It appears better suited to temperate and subtropical climates. This taxon is cultivated on a commercial scale.

– var. tenacissima (Roxb.) Miq. (‘Green ramie’ or ‘Indian ramie’; synonym: Boehmeria tenacissima Gaudich.) is believed to originate from Malaysia, and has smaller leaves which are green on both sides. It appears better suited to tropical climates. Green ramie might be a derivative of a cross between white ramie and an unknown species.

Ramie is grown as a perennial crop. The rhizome starts to grow 5–20 days after planting. The storage roots are produced in early stages of growth. Harvesting may start 3–10 months after planting out the rhizomes, but the first harvest of a new plantation is often not used for fibre because of uneven growth and low fibre quality. Ramie is cross-pollinated. The male flowers open first and pollination is by wind.

Ramie is grown at average temperatures ranging from 20°C during the cropping season in temperate regions to 28°C in the tropics. Frost may destroy the rhizomes; this can be prevented by mulching with leaves or compost. To grow properly, ramie requires a minimum of 100–140 mm rainfall per month. Short days promote flowering and ramie tolerates partial shade. For optimal fibre production ramie requires rich, well-drained, sandy loams, with a pH of 5.5–6.5. With heavy manuring it can also be grown on less favourable soil types. Ramie is extremely sensitive to waterlogging.

Ramie can be propagated by seed, but the resulting plants take 1–2 years to become productive and are often inferior to their parents. Therefore, ramie is usually propagated vegetatively by means of rhizome cuttings 15–30 cm long, taken from plants at least 3 years old. To ensure optimal growth, the rhizomes should be planted out as soon as possible after being cut. If immediate planting is impossible, they should be kept moist and covered and in a shaded place. The rhizome cuttings are usually planted manually in a well-prepared seed-bed at a depth of 5–7.5 cm. Planting distances vary widely, depending on soil fertility, cultivar and availability of planting material. The spacing between rows is 25–140 cm and that within the row 5–60 cm. Ramie can also be propagated by division, air layering and stem cuttings. In-vitro propagation is possible, as complete plants have been regenerated from callus produced from ramie cotyledons, leaves, stem segments, leaf segments and hypocotyls.

Ramie needs regular weeding until the canopy is closed. Weeding of ratoon crops usually starts during the harvest of the preceding crop, when not only the ramie but also the weeds are cut. Because of its high productivity ramie rapidly depletes soil nutrients. Fertilization with manure or inorganic fertilizer, especially with nitrogen, is important for satisfactory yields. Leaving or returning leaves and other residues on or to the field is beneficial, because these materials contain a large proportion of the nutrients removed. The production of 45 t fresh plant material (1.5 t fibre) on a peat soil in Florida (United States) resulted in the removal of about 206 kg N, 19 kg P, 100 kg K, 230 kg Ca and 52 kg Mg. A general recommendation in the Philippines is to fertilize a plantation of 50,000 plants/ha with 90 kg N, 26 kg P and 50 kg K per harvest per ha on sandy or clay loams and with 60 kg N, 13 kg P and 25 kg K on soils rich in organic matter, and to return all plant waste to the field after fibre extraction. In some countries, replanting is done every 7 years whereas in parts of China the crop is maintained as long as 20 years.

No information is available on the diseases and pests affecting ramie in tropical Africa. The most serious disease of ramie in Asia is ‘white fungus disease’ caused by Rosellinia necatrix. Other diseases known to attack ramie include angular leaf spot caused by Pseudocercospora boehmeriae, stem rots caused by Corticium rolfsii (synonym: Sclerotium rolfsii), Macrophomina phaseolina, Phoma boehmeriae and Rhizoctonia solani, and leaf spots caused by Cercospora spp. Many insects feed on ramie leaves, but there are few serious pests. The most widespread are leaf rollers (Sylepta spp.), found in almost every country where ramie is grown.

The root-knot nematode Meloidogyne incognita occurs regularly in ramie. It can be detected by the presence of galls on the roots. Severely infected plants are stunted and have yellow leaves. Other nematodes harming ramie include the lesion nematode (Pratylenchus sp.), stunt nematode (Tylenchorhynchus sp.) and reniform nematode (Rotylenchulus sp.).

The timing of the harvest of ramie is crucial: if stems are immature, the fibre yield is reduced; if stems are too mature, it is difficult to remove the fibre. Harvesting is usually carried out when the stems start turning brown and growth slows down. In temperate regions ratoon crops can be harvested 2–3 times a year, in subtropical areas 4–5 times, and in tropical areas up to 7 harvests a year are possible. However, the yield per harvest is usually higher in temperate regions, and it is possible that more fibre is obtained per ha per year from 2–3 harvests in temperate regions than from more harvests in tropical areas. The plants are usually harvested manually with a sickle close to the ground to prevent new stalks arising from the old stump. In some areas the stems are bent over to break the core and the cortex is stripped from plants in the field. Mechanical harvesters have been developed but are not used commercially. At harvesting, the tops and the leaves may be removed from the stems and used as animal feed or green manure.

The fresh stem yield of ramie is normally 45–60 t per ha per year, giving about 2000 kg dried fibre and 1500 kg degummed fibre. For the Philippines yields have been recorded of 2000 kg dried fibre per ha in the first year after planting and 3500 kg in subsequent years. Yields start to decline when plantings become overcrowded; at this point the rhizomes may be pruned, e.g. by ploughing, or the area may be replanted.

When grown for fodder, the yield may amount to 300 t fresh material or 42 t dry matter per ha per year in up to 14 cuts.

Ramie is processed into fibre in one or two steps: the first being extraction, the second being degumming. Extraction is usually done manually by defoliating the stems and removing the entire raw bast ribbon, which is then scraped to remove the outer bark, non-fibrous parenchyma and much of the gummy material. Manual extraction is very labour intensive, and in Brazil, Japan and parts of the Philippines ramie is decorticated mechanically using machines based on the same principles as those used for kenaf (Hibiscus cannabinus L.) or sisal (Agave sisalana Perrine). Ramie fibre cannot be extracted satisfactorily by retting, because of the presence and nature of large amounts of gums in the bark, though some bacteria have been found to decompose the gums. The fibres are extracted when the stems are still fresh, because the bark is more difficult to remove when the plant dries. If extraction cannot be done immediately after harvesting, the stems are kept in water to keep them fresh. Extracted fibres are hung over poles for 1–3 days to dry and bleach in the wind and sun. Drying is done as soon as possible, to prevent attack by fungi and bacteria. After being dried, the fibres may be brushed to reduce the gum content. Undegummed ramie fibre may be used for coarse ropes for marine applications, sacks and other containers and rugs and carpets. There are no universally accepted grades, and each country has its own way of grading.

Degumming is necessary to remove the gums contained in the raw ramie fibre. The presence of gums makes the fibre stiff and brittle, and they must be removed before the fibre can be combed and spun into fine yarns. In areas where processing is manual, this may be done by repeated soaking, scraping, washing and sun-drying. Other methods include treatment with soap solution, lime or chemicals. Many chemical degumming methods have been developed, but they are usually kept secret by the textile mills using them. Usually they contain the same basic steps: boiling in an aqueous alkaline solution; washing with water; bleaching with an oxidizing agent; washing with water; and oiling with a sulphonated hydrocarbon. If carried out incorrectly, degumming can reduce the strength of ramie fibre and increase its brittleness. The chemical degumming process produces polluting effluents. Combined microbial and chemical degumming processes have been proposed to reduce the use of chemicals and energy, and to improve the resulting fibre quality, but they have not yet been applied on industrial scale.

In industrialized regions, ramie is commonly spun on machinery developed for silk, wool or cotton. The results are often less satisfactory, however. When a short-fibre spinning system like the one used for cotton is used, ramie fibre has to be cut short (‘stapling’).

The Institute of Bast Fiber Crops of the Chinese Academy of Agricultural Sciences (CAAS) in Yuanjiang, China, has a collection of about 1300 ramie accessions, and characterizes and evaluates botanical and agronomical characters, fibre yield, quality and stress resistance. More than 1000 accessions have been planted in the field in Yuanjiang to create the ‘National Ramie Germplasm Field Genebank’. Germplasm collections are also available at the Instituto Agronômico de Campinas (IAC), São Paulo, Brazil and the Institute of Plant Breeding of the University of the Philippines Los Baños.

Ramie is a clonal crop, so the breeding methods applied are similar to sugar cane or potato. Seedlings are mostly very inferior in quality and to obtain improved cultivars initial recombination crossing has to be followed by a long programme of clonal selection. Selection work on ramie has been carried out in various countries, including the Philippines and Indonesia. In China, the Institute of Bast Fibre Crops has selected and distributed more than 30 elite accessions. In India 5 cultivars were selected on the basis of yield, gum content, fertilizer response and resistance to stress, and the most popular of these (‘R 67–34’) has been released. Important considerations in ramie selection are: adaptation to ecological conditions, decortication characteristics, leafing and branching characteristics, resistance to diseases and pests, tendency to lodge and fibre characteristics (uniformity, strength, fineness and colour).

In Brazil a protocol has been developed for the genetic modification of ramie and experiments are being carried out to improve the amino acid composition and thus the fodder value of ramie through genetic modification. In China genetic transformation of ramie plants has been achieved by Agrobacterium-mediated methods.

Because of the difficulties and costs involved in the production and processing of ramie, it is unlikely that the crop will become a major trade commodity and challenge the established major natural and synthetic fibres. However, the excellent properties of its fibre and the wide range of possible uses make ramie a promising cash crop for the local market in many tropical and subtropical countries. The development of new technologies such as decorticating and stripping machines and degumming processes suitable for medium- and small-scale operations, may improve the chances of ramie becoming more important as a fibre crop. The medicinal properties of Boehmeria nivea seem to justify more research.

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• M. Brink, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Brink, M., 2011. Boehmeria nivea (L.) Gaudich. [Internet] Record from PROTA4U. Brink, M. & Achigan-Dako, E.G. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 22 December 2024.

• See the Prota4U database.