Boehmeria nivea (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

Boehmeria nivea (L.) Gaudich.

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

Family: Urticaceae

Chromosome number: 2n= 24 (cv. group Green Ramie), 28 (cv. group White Ramie).

Synonyms

Urtica nivea L. (1753), Boehmeria tenacissima Gaudich. (1830), B. utilis Blume (1853).

Vernacular names

• Ramie, rhea, China grass (En). Ramie (Fr)
• Indonesia: rami (Indonesian), haramay (Sundanese)
• Malaysia: rami, rami-rami
• Philippines: amirai (Tagalog), labnis (Ilokano), lipang-aso (Tagalog)
• Cambodia: thmey
• Laos: pan
• Thailand: po-paan (central), po-bo (northern), taan khamoi (southeastern)
• Vietnam: cây gai.

Origin and geographic distribution

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 18th 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, including the Philippines, Indonesia, Malaysia, Thailand, Vietnam, Cambodia and Laos. It has occasionally escaped from cultivation and naturalized.

Uses

Fibre from the stem of ramie is one of the oldest textile fibres, used since prehistoric times in China, India and Indonesia, and mentioned and praised in Sanskrit poems. In China it has been used for paper making for many centuries. Nowadays ramie fibre serves locally for the production of ropes, strings, fishing lines and nets, sewing thread and fabrics. Its traditional use in South-East Asia is mainly for fishing lines and nets which are durable in sea water. 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, e.g. for 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 may be fed to cattle, sheep, goats, pigs, rabbits and chickens. The main parts used as fodder are the leaves and stem tops that are by-products of fibre extraction. 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 ("banh gai") which is considered a delicacy. 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.

Production and international trade

Despite its high fibre quality and diverse uses, ramie has not become a major world textile, because the difficulties and high costs of production and processing lead to irregular supply, uneven quality and high prices. Commercial production in the Philippines started in the 1930s, when China prohibited ramie exports temporarily, and peaked at about 5500 t per year in the 1960s. In the late 1960s and 1970s Brazil expanded its production, reaching a peak of about 30 000 t from about 20 000 ha in 1970 and 1971. Production in the Philippines declined to about 3000 t per year in the early 1970s, but recovered in the 1980s; in the late 1980s up to 10 000 ha were planted with ramie there. According to FAO estimates the world ramie fibre production in the period 1996-2000 was about 140 000 t per year, cultivated on about 90 000 ha, with more than 90% produced in China. In this period Brazil produced 2400 t per year, the Philippines 1600 t and Laos 1400 t.

Most of the ramie produced is used in the producing countries and only a small proportion enters international trade (on average about 3000 t per year for the period 1996-2000). The main exporters in this period were China (about 2000 t per year), Indonesia (300 t/year) and Brazil (100 t/year). The major importer is Japan (1800 t per year in 1996-2000). The highest quality ramie available on the world market is produced in the Philippines, mainly because of the superior processing equipment employed.

Properties

Ramie fibres, classified as nonlignified soft fibres, lie in bundles in the bast layer of the stem and can be stripped in the form of ribbons. The ultimate fibre cells are (10-)40-250(-600) mm long and (10-)25-60(-100) 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 fibres contain 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 fibres contain 96-98% α-cellulose.

Ramie fibre is strong, lustrous and durable. The tensile strength, absorbency, drying properties and dyeing qualities of ramie fibre are often indicated as being 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. Typical values of the tensile strength, elongation at break, and Young's modulus of ramie fibre are 400-940 N/mm², 3.6-3.8% and 61.4-128.0 GPa, 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 weight 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 weight, whereas total plant residues after fibre extraction contain about 13 g. The digestible protein contents of 4- and 6-week-old ramie (stems and leaves) in Thailand were 86 g and 52 g per kg dry matter, respectively. The net energy contents of 4- and 6-week-old plants were 381 and 331 starch equivalent per kg dry matter. Meal made of ramie leaves and tops contains 21-22% crude protein.

Adulterations and substitutes

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

Description

A monoecious, erect, fast-growing perennial herb or small shrub, 1-2(-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, the bast layer yielding the ramie fibre. Leaves alternate, simple, with 3 prominent basal veins; stipules axillary, connate at base, linear-lanceolate, up to 1.5 cm long; petiole 6-12 cm long, pubescent; blade broadly ovate, triangular to suborbicular, 7-20 cm × 4-18 cm, base cuneate to subcordate, margin coarsely dentate to dentate-serrate or crenate, apex usually abruptly long-acuminate, green and scabrid above, glabrous and green or white appressed-pubescent below. Inflorescence axillary, racemose, paniculate, 3-8 cm long, each branch bearing several crowded or well-separated clusters of unisexual flowers, 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; 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 one ovule, style exserted, slender and hairy on one side, stigma filiform. Fruit a subglobose to ovoid achene, about 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.

Growth and development

The rhizome of ramie 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. In Java flowering is year-round.

Other botanical information

Considerable variation exists within B. nivea and this variation has been described as different species, subspecies, varieties or forms. For the cultivated forms it is, however, most appropriate to distinguish the following 2 cultivar groups:

• cv. group White Ramie (also named Boehmeria nivea (L.) Gaudich. var. nivea , Chinese ramie or China grass). This group, originating from China and Japan, 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 group is cultivated on a commercial scale.

• cv. group Green Ramie (also named Boehmeria nivea (L.) Gaudich. var. tenacissima (Roxb.) Miq., B. tenacissima Gaudich., B. utilis Blume, Indian ramie or rhea). This group, believed to originate from Peninsular Malaysia, 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 a White Ramie cultivar and an unknown species.

There are numerous ramie cultivars, many originating from Japan, where ramie research started in the early 1900s. The most popular and widely used cultivar in the Philippines is "Seikeiseishin", introduced from Japan, maturing in 45-60 days and yielding on average 3 t/ha of a strong, fine fibre, suitable for spinning fine yarns. Other cultivars grown in the Philippines are "Miyazaki 112", "Chuma", "Everglades", "Formosa" and "Guiran Taipan No 1". Indonesian cultivars include "Pudjon 10", "Bandung A", and "Lembang A", developed in Java, and "Pantjur Batu", developed in Sumatra.

B. holosericea Blume is occasionally grown as a fibre plant in Korea, whereas B. grandis (Hook & Arnott) Heller has been cultivated in Hawaii as a source of barkcloth.

Ecology

Ramie is found from almost equatorial conditions in Indonesia and the Philippines to about 38N in Japan and South Korea. It 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 (4.8-5.6 for peat soils). With heavy manuring it can also be grown on less favourable soil types. Ramie is extremely sensitive to waterlogging. In Philippine experiments it was most sensitive to flooding immediately after cutting and least sensitive during the middle vegetative stage (20 days after cutting). The duration of flooding significantly affected the height, stem weight and dry fibre yield, but had no significant effect on the fineness or diameter of the fibre.

Propagation and planting

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 ranges from 25-140 cm and that within the row from 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.

Except for the large estates in the Philippines and Brazil, ramie plantings are usually small family plots.

Husbandry

Ramie needs regular weeding until the canopy is closed. Weeding of ratooned crops usually starts during the harvest of the preceding crop, when not only the ramie but also the weeds are cut. In the Philippines the crop is sometimes irrigated. 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 results in the removal of about 206 kg N, 19 kg P, 100 kg K, 230 kg CaO and 52 kg MgO. 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.

Diseases and pests

The most serious disease of ramie is "white fungus disease" caused by Rosellinia necatrix . It occurs in the Philippines, Vietnam and Japan. By the time the symptoms of wilting leaves are visible, the root system has been destroyed and the dead roots are covered with a white veil of thread-like forms. Infested areas should be dug up, burned and disinfected (e.g. with a chloropicrin solution). In Indonesia angular leaf spot caused by Pseudocercospora boehmeriae is a serious disease that retards growth. Other diseases known to attack ramie include stem rots caused by Phoma boehmeriae , Rhizoctonia solani , Macrophomina phaseolina , Sclerotium rolfsii and Corticium rolfsii , and leaf spots caused by Cercospora spp.

Many insects feed on ramie leaves, but there are few serious pests. The most serious and widespread are leaf rollers ( Sylepta spp.), found in almost every country where ramie is grown. The larvae feed on the leaves, roll them up and pupate in the rolled leaves. Heavy infestation results in complete defoliation, growth cessation and undesirable secondary growth. In the Philippines, Indonesia and Japan ramie is attacked by the black caterpillar Cocytodes coerulea , which may defoliate large patches in the field. The larvae are removed either manually or by spraying. In the Philippines ramie is one of the crops damaged by the golden apple snail ( Pomacea sp.).

The root-knot nematode Meloidogyne incognita occurs regularly in ramie, e.g. in the Philippines and in India. 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.). Nematode control is difficult; sometimes the fungus Paecilomyces lilacinus is used as a biological control agent.

Harvesting

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.

Yield

The fresh stem yield of ramie is normally 45-60 t per ha per year, giving 1000-1600 kg dried fibre and 500-1200 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. In some countries, replanting is done every 7 years whereas in parts of China the crop is maintained as long as 20 years.

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.

Handling after harvest

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. In Indonesia the outer bark may be scraped from the over-mature stalk, leaving the fibre, The stalk is washed and dried for several days, after which the fibre is peeled off in strands. 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. The main Philippine grades are RD-A ("Ramie Special"; fibres 80 mm or longer; well cleaned; colour straw to creamy), RD-1 ("Ramie Good"; fibres 80 mm or longer; well cleaned; colour brownish), RD-2 ("Ramie Fair"; fibres 80 mm or longer; fairly cleaned; colour light brown and RD-3 ("Ramie Short"; fibres 40-80 mm long). Minor Philippine grades include RD-O (string), RD-T (tow) and RD-W (waste). Most farmers in the southern Philippines produce RD-1 and RD-2, because the leaves and tops are not removed before decortication.

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. Furthermore, 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 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").

Genetic resources

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. In total, 1017 indigenous accessions and 10 other 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 (460 accessions) and the Institute of Plant Breeding of the University of the Philippines Los Baños (56 accessions).

Breeding

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.

Prospects

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.

Literature

 1 Brühlmann, F., Leupin, M., Erismann, K.H. & Fiechter, A., 2000. Enzymatic degumming of ramie bast fibers. Journal of Biotechnology 76(1): 43-50.

• Dempsey, J.M., 1975. Fiber crops. University Presses of Florida, Gainesville, Florida, United States. pp. 90-128. 3 Greenhalgh, P., 1979. Ramie fibre: production, trade and markets. Tropical Science 21(1): 1-9.
• Jarman, C.G., Canning, A.J. & Mykoluk, S., 1978. Cultivation, extraction and processing of ramie fibre: a review. Tropical Science 20(1): 91-116.
• Kirby, R.H., 1963. Vegetable fibres: botany, cultivation, and utilization. Leonard Hill, London, United Kingdom & Interscience Publishers, New York, United States. pp. 148-180. 6 Koopmans, A., 1989. Boehmeria nivea (L.) Gaudich. In: Westphal, E. & Jansen, P.C.M. (Editors): Plant Resources of South-East Asia: a selection. Pudoc, Wageningen, the Netherlands. pp. 59-61. 7 Machin, D.H., 1977. Ramie as an animal feed: a review. Tropical Science 19(4): 187-195.
• Sarma, B.K., 1981. Diseases of ramie (Boehmeria nivea). Tropical Pest Management 27(3): 370-374. 9 The Publication Production Committee for Ramie, 1988. The Philippines recommends for ramie production. PCARRD Technical Bulletin Series No 62. Philippine Council for Agriculture, Forestry and Natural Resources Research and Development (PCARRD), Fiber Development Authority (FIDA) and University of Southern Mindanao (USM), Los Baños, Laguna, the Philippines. 43 pp. 10 Wood, I.M., 1993. Fibre crops: new opportunities for Australian agriculture. Queensland Department of Primary Industries, Brisbane, Australia. pp. 59-64.

Authors

R.P. Escobin