Cymbopogon winterianus (PROSEA)

Plant Resources of South-East Asia Introduction

List of species

1, habit of one leafy culm; 2, part of inflorescence; 3, pair of spikelets.

Cymbopogon winterianus Jowitt

Protologue: Ann. Roy. Bot. Gard. Peradeniya 4: 188 (1908).

Family: Gramineae

Chromosome number: 2n= 20, 40

Synonyms

Cymbopogon nardus (L.) Rendle var. mahapangiri auct.

Vernacular names

• Java citronella grass, winter's grass, old citronella grass (En).
• Herbe citron de Java (Fr)
• Indonesia: serai wangi (general), sere wangi (Javanese), sereh wangi (Sundanese)
• Malaysia: serai wangi
• Thailand: takhrai ma-khuut (northern), takhrai-hom (central), takhrai-daeng (peninsular)
• Vietnam: sả Java, sả dỏ.

Origin and geographic distribution

C. winterianus is only known from cultivation and most probably originated in southern India or Sri Lanka. C. winterianus was brought to Java at an early date and was taken into cultivation before 1900. Large-scale production and the use of improved selections and distillation equipment in Java started around 1900. At present C. winterianus is cultivated throughout the tropics. In South-East Asia it is important in Indonesia and Vietnam and elsewhere in Brazil, China, Ghana, Guatemala, Haiti, Honduras and India.

Uses

Java citronella oil distilled from the leaves of C. winterianus is a very widely used aroma material in perfumery and cosmetics, either directly or as a starting material for the production of other aroma compounds. The complete oil is mainly used as an insect repellent for humans and pets and is applied in soaps, detergents, household insecticides and technical products. d-Citronellal from the oil, which has few direct perfumery uses, is often converted into l-menthol or hydroxycitronellol. The latter is used in floral and non-floral fragrances (odour of lily of the valley). Geraniol from citronella oil is sometimes converted into citronellol and its esters, which are respectively major components and modifiers of floral fragrances. In traditional medicine, poultices of the leaves are applied to treat minor cuts and bruises, while extracts are used against internal disorders and as a vermifuge. The extracts are also mildly astringent and stomachic. In Thailand a preparation of crude citronella oil mixed with leaves of Azadirachta indica A.H.L. Juss. and rhizomes of Alpinia galanga (L.) Willd. is applied as a bio-insecticide in vegetable production and in citrus orchards. C. winterianus is sometimes planted to control erosion or to provide mulch.

Production and international trade

The annual world production of citronella oil is estimated at 5000 t, valued at about 19 million US$ (1997). Most citronella oil is Java citronella oil; production of Ceylon citronella oil is restricted to Sri Lanka and is only 200 t/year. After C. winterianus was introduced into Java, Java citronella oil gained an excellent reputation in the world market. Later, the planting of mixtures and hybrids of C. winterianus and C. nardus (L.) Rendle and the marketing of adulterated oil spoiled the good name of Java citronella oil. Through strict control of production and marketing between the First and Second World Wars, Java regained its reputation for quality and dependability and average exports between 1989-1995 ranged from 560-650 t.

C. winterianus was taken to Taiwan, where a large industry developed, mainly exporting to Japan. However, after a peak of 3000 t in 1965, production fell rapidly due to industrialization, and by 1984 it had all but ceased. Production in China is concentrated in Hainan Island; it reached a peak in 1957, but citronella production was subsequently partly replaced by more profitable essential-oil crops. In Central America, Guatemala is the main producer. It started citronella production at the end of the 19th Century with a boom during the second World War, but production rapidly declined when oil from Java became available again. Later, production recovered. Other countries producing and exporting citronella oil are Brazil, Guatemala, Ghana, Honduras, India and Vietnam.

Properties

The leaves of C. winterianus contain 0.25-1.3% citronella oil, which is an almost colourless or pale yellow liquid, with a fresh and sweet rosy top note, a body with notes of rose and lemon and a sweet, somewhat woody dry-out. It is free of the camphene-borneol notes characteristic of Ceylon citronella oil. The major chemical components of Java citronella oil are citronellal, geraniol, elemol, geranyl acetate, limonene,β-elemene, citronellyl acetate and eugenol. The composition of the oil changes with leaf age. Comparison of citronella oils originating from Java, China and Latin America indicated a remarkable similarity in chemical composition; only oil from Sri Lanka and Burma (Myanmar) showed much lower citronellal content. Contrary to the uniformity in major components, there is considerable variation in minor constituents in oils from different origins, and in perfumery they are differentiated accordingly.

Citronella oil has been approved for food use by the Food and Drug Administration of the United States under paragraph 182.20 and has been "generally recognized as safe" (GRAS No 2308); it is registered by the Council of Europe under No 39n. A monograph on its physiological properties has been published by the Research Institute for Fragrance Materials (RIFM). See also: Composition of essential-oil samples and the Table on standard physical properties.

Adulterations and substitutes

Java citronella oil is not often adulterated as its price is lower than that of most other aroma materials. The oil of Corymbia citriodora (Hook.) K.D. Hill & L.A.S. Johnson (synonym: Eucalyptus citriodora Hook.), which also contains a high proportion of citronellal (about 80%), is used as an alternative source of citronellal for industrial purposes.

Description

• Perennial, tufted, aromatic grass with numerous erect culms arising from a short rhizome. Culm (stem) up to 2.5 m tall, terete, smooth, glabrous.
• Leaves sheathing; sheath striate, glabrous, smooth, yellowish or turning purplish-red, those of the culm tightly clasping and shorter than the internodes, those at the base very short, loose, slipping from the culm; ligule chartaceous, about 1 mm long, ciliate; blade linear with long filiform tip, up to 1 m × 1.5(-5) cm, drooping for 2/3 of their length, smooth and glabrous, light green on upper surface, glaucous below, margins often scabrid-serrate.
• Inflorescence a large, repeatedly branched panicle, 60-100 cm long, axis zigzag, branches of the highest order ending in a spatheole subtending a pair of racemes; spatheole linear-lanceolate, 1-2.5 cm long, many veined, dull reddish; racemes 1-2 cm long, ciliate, one subsessile, the other one stalked, consisting of 4-7 pairs of spikelets, 1 of each pair sessile, the other pedicellate, terminated by 1 sessile and 2 pedicellate spikelets.
• Sessile spikelet oblong-ellipsoidal, 4-5 mm long, with 2 florets; lower glume oblong-lanceolate, shape and size of the spikelet, usually flat, narrowly winged, 2-keeled, 0-3-veined; upper glume boat-shaped, keeled in the upper half, 3-veined; lower floret reduced to empty lemma; upper floret hermaphrodite, lemma 3 mm long, hyaline, 2-lobed, awn up to 5 mm long if present, palea absent, lodicules 2, stamens 3, styles 2 with plumose stigmas.
• Pedicellate spikelet narrowly oblong-ellipsoidal, up to 5 mm long, male or sterile; lower glume shape and size of the spikelet, 7-9-veined; upper glume equal in size, 3-veined; florets represented by a single hyaline scale 3 mm long, wrapped round 3 stamens and 2 lodicules.
• Fruit a cylindrical to subglobose caryopsis, with basal hilum.

Growth and development

Splits of a clump of C. winterianus root easily, usually within 3 weeks after planting and tillering starts after the 4th week. Clumps of C. winterianus can become up to 0.5 m in diameter and economic lifetime is about 6 years. Flowering starts about 8 months after planting, but plants are cut preferably just prior to flowering. Many cultivars of C. winterianus , if allowed to flower, do not produce viable seed. Viviparous formation of plantlets has been observed in inflorescences that had flowered before the start of the rainy season. The plantlets appear to arise from the nodes or the axil of the spatheoles. They sometimes produce their own inflorescence while still attached to the mother plant. The oil content of leaves can differ considerably, depending on age, time of cutting and soil fertility (0.25-1.3%); essential oil content is highest in young leaves.

Other botanical information

The name citronella grass refers mainly to 2 grasses producing citronella oil: C. nardus (L.) Rendle (Ceylon citronella grass or lenabatu) and C. winterianus. Both are morphologically very similar, probably closely related and sometimes even considered as one species. However, C. winterianus differs in its wider, shorter and less harsh leaves, its much looser inflorescence, and its distinct venation of the lower glume of the hermaphrodite spikelets. Moreover, the oil of C. winterianus differs so much in composition, characteristics and odour that the two oils are neither substitutes nor alternatives to each other. The oil of C. nardus is of poorer quality, but because the plant is better adapted to local circumstances (e.g. poor soils and periods of drought) it is preferred for cultivation in Sri Lanka. Occasionally, C. nardus is also grown outside Sri Lanka for its essential oil, e.g. in Java, especially var. confertiflorus (Steudel) Bor (synonym: C. confertiflorus (Steudel) Stapf). Commercially, however, this taxon has no importance. C. winterianus also closely resembles C. flexuosus (Nees ex Steudel) J.F. Watson (East Indian lemongrass), but the essential oil of the latter is different, being characterized by neral and geranial.

Several high-yielding cultivars have been developed in India. In 1987, "Mandakini", suitable for the foothills of the Himalayas, and "Manjusha", suitable for the North Indian Plains were released. They outyield the best older cultivars by 60% and 30%, respectively. Later, a new cultivar, named "Bio-13", was developed through tissue culture. It is superior in yield to "Mandakini" and "Manjusha" and its essential oil has a very high citronellol and geraniol content.

Ecology

C. winterianus is grown throughout the tropics and warm subtropics, provided moisture is amply available. A total annual rainfall of 2000-2500 mm evenly distributed over the year is needed for good, sustained yields. Where there is a pronounced dry season, irrigation is required if C. winterianus is to persist. The oil from leaves harvested after a dry period tends to have an increased aldehyde content. Generally, C. winterianus is found below 500 m altitude. However, in India, cultivars adapted to higher altitudes have been selected that yield well up to at least 1200 m, e.g. in tea-growing areas in Assam. Average daytime temperatures of 22-27°C are optimal for growth. Low temperatures retard growth and may reduce leaf-oil content. Even light frost causes severe damage and serious frost is often lethal. Hail storms can severely damage young plantations and cause damage to the leaves in older plantations reducing the oil content. C. winterianus requires more fertile soils than the other Cymbopogon grasses and on poor soils its economic life is short. It prefers neutral to slightly acid, well-drained, loamy soils with an adequate supply of moisture and nutrients. It tolerates only short periods of waterlogging and is intolerant of salinity.

Propagation and planting

C. winterianus is generally propagated vegetatively, as propagation by seed takes a long time and carries the risk of including hybrids of C. winterianus and C. nardus. Offshoots for planting are obtained by division of clumps. Clumps 1 year old give 50-60 rooted splits and 1 ha of clumps is normally adequate to plant 7-8 ha. Hormones or fungicides are rarely applied, as offshoots strike root easily and it is simple and cheap to replace dead plants. Plantlets are placed about 10 cm deep in a hole which is filled in gradually to prevent the crown from rising above ground level. Soil should be well compacted around the young plants. Planting is usually in a square arrangement at a spacing of 60-90 cm × 60-90 cm. Close spacing is most common and generally results in less weed growth and higher yield. C. winterianus is sometimes intercropped with young rubber, cocoa, pepper or vanilla or underplanted in tall tree plantations. The degree of canopy shade determines the reduction in herbage yield.

Husbandry

Weeds can be controlled by hand or mechanically, manual weeding being generally more effective. Special care is needed to remove lalang grass (Imperata cylindrica (L.) Raeuschel). Cultivation should be superficial to avoid damaging the shallow root system or uprooting young plants. No herbicides are recommended for use in C. winterianus, but 2,4-D is sometimes applied 2 weeks before planting and several herbicides have been used for spot-spraying after harvesting.

As large amounts of nutrients are removed with the leaves, regular application of fertilizer is essential for sustained production. In experiments, N applications of up to 400 kg/ha per year have given the highest yields. A general recommendation is to apply annually per ha 80-120 kg N, 40 kg P₂O₅and 40 kg K₂O. In areas where the crop grows actively throughout the year, the recommendation is double these amounts. N applications are always split and are given after harvest. Many small farmers, however, rarely apply any fertilizer at all and abandon the crop when yield drops to an uneconomic level. Larger oil producers in Java have adopted a rotation of 4 years of C. winterianus alternating with 2 years of a green manure crop, often a Tephrosia or Mimosa species.

Diseases and pests

Leaf blight caused by Curvularia andropogonis may cause serious reductions in leaf and oil production of Java citronella grass. Initial symptoms consist of brownish patches on the tips and margins of leaves, which may dry out later. Prophylactic spraying with dithiocarbamates at intervals of 10-15 days can effectively control the disease. Anthracnose caused by Colletotrichum graminicola may also cause damage and is controlled similarly. In Latin America, sugar cane mosaic virus is the most important disease. No serious pests have been reported.

Harvesting

The first harvest of C. winterianus is usually taken 6-12 months after planting and subsequently 3-4 times per year, depending on the rate of regrowth. In Indonesia, up to 6 cuts per year are sometimes possible, but 4 annual harvests give the highest oil yield. In northern India, the timing of harvesting is related to the onset and duration of the monsoon. In Assam, crops planted in April-May are first harvested after 3-4 months and subsequently every 2 months. During the dry winter season (November-February), only 2 harvests are taken. Many farmers use plant height as an indicator of the best time for harvesting. In Guatemala a crop 140 cm tall is considered ready for harvesting. C. winterianus can be harvested for up to 5-6 years, but it is generally more economical to replace a crop after 4 years.

Yield

Annual herbage yield of Java citronella grass varies greatly, and may range from 10-30 t/ha. Oil yield also varies considerably between the dry and wet seasons. In India, it ranges from 0.5-0.6% (dry season) to 0.3-0.35% (wet season), in Java from 1.2% (dry season) to 0.5% (wet season), Guatemala and Honduras from 1.8% (dry season) to 0.75% (wet season). Average annual oil yield in Java is estimated at 45-80 kg/ha, in Guatemala at 110 kg/ha. The yield of citronella oil also depends on the distillation procedure.

Handling after harvest

After harvesting, the crop is first left in the field to wilt and dry. In Indonesia, drying in the sun for 3-4 hours is usual, except when the grass is very wet after a rainy period. In Sri Lanka and India the crop may be left to dry for 1-2 days. In the Philippines, lowest moisture and highest oil yield were found after drying for 7 days; elsewhere the crop is sometimes left for up to 1 month without much loss in yield. Rapid withering in the sun may slightly increase the monoterpene content. Steam distillation is used to extract the oil from the leaves. Steam pressure varies per country; in Thailand a steam pressure of 150 kPa is recommended, in Sri Lanka 100-200 kPa. In Honduras an initial pressure of 650 kPa is applied, reduced to 250 kPa when condensation begins and raised to 1000 kPa when the condensate flows evenly. The duration of distillation varies with steam pressure and the capacity of the still; a load of 500-600 kg is distilled for about 2 hours. Spent grass is sometimes spread over the field as mulch or used to fuel the still.

Genetic resources

Several institutions in South and South-East Asia are involved in germplasm collection and conservation of aromatic grasses. Systematic collection of germplasm of Cymbopogon was initiated at the Lemongrass Breeding Station, Odakkali, Kerala, India as early as 1951. The collection now has over 450 accessions. Other major institutions include: the Research Institute for Spice and Medicinal Crops (RISMC), Bogor, Indonesia; the Thailand Institute of Scientific and Technological Research (TISTR), Bangkok, Thailand; the University of the Philippines, Los Baños, the Philippines; the Central Institute of Medicinal and Aromatic Plants, Lucknow, India and the National Board of Genetic Resources, New Delhi, India.

Breeding

In India, cultivars of C. winterianus adapted to North Indian and South Indian conditions have been developed. Mutation breeding techniques using irradiated plant material have been tried. This resulted in genetic divergence including changes in oil composition, but has not resulted in improved cultivars.

Prospects

In spite of its very low price, Java citronella oil is still one of the most widely produced essential oils. Most of the oil is used for industrial purposes and has to compete with synthetic products. Any increase in production cost may lead to an increase in selling price and a reduction in demand and to the cultivation of alternative crops.

Literature

• Boelens, M.H., 1994. Sensory and chemical evaluation of tropical grass oils. Perfumer and Flavorist 19: 29-45.
• Bor, N.L., 1953, 1954. The genus Cymbopogon Spreng. in India, Burma and Ceylon. Journal of the Bombay Natural History Society 51: 890-916 (Part 1, 1953); 52: 149-183 (Part 2, 1954).
• Husain, A., 1993. Present and future of agrotechnology of essential oil plants in India. In: Dhar, K.L., Thappa, R.K. & Agarwal, S.G. (Editors): Newer trends in essential oils and flavours. Tata McGraw-Hill Publishing, New Delhi, India. pp. 174-193.
• Ng, T.T., 1972. Growth performance and production potential of some aromatic grasses in Sarawak - a preliminary assessment. Tropical Science 14: 47-58.
• Sahoo, S. & Debata, B.K., 1995. Recent advances in breeding and biotechnology of aromatic plants: Cymbopogon species. Plant Breeding Abstracts 65: 1721-1731.
• Sharma, J.R., 1993. Trends in genetic degradation of aromatic plants. In: Dhar, K.L., Thappa, R.K. & Agarwal, S.G. (Editors): Newer trends in essential oils and flavours. Tata McGraw-Hill Publishing, New Delhi, India. pp. 249-268.
• Singh, M., Ganesha Rao, S., Prakasa Rao, E.V.S., 1996. Effect of depth and method of irrigation on herb and oil yields of Java citronella (Cymbopogon winterianus Jowitt) under semi-arid tropical conditions. Journal of Agronomy and Crop Science 177: 61-64.
• Soenarko, S., 1977. The genus Cymbopogon Sprengel (Gramineae). Reinwardtia 9: 225-375.
• Weiss, E.A., 1997. Essential oil crops. CAB International, Wallingford, United Kingdom. pp. 67-86.

Composition of essential-oil of Java citronella oil

• 34.8% citronellal
• 23.2% geraniol
• 11.2% citronellol
• 5.1% geranyl acetate
• 3.2% elemol
• 2.8% limonene
• 2.5% eugenol
• 2.3% β-cubebene
• 2.0% β-elemene
• 1.9% citronellyl acetate
• 1.7% γ-cadinene
• 1.2% δ-cadinene
• 0.7% linalool
• 0.7% γ-muurolene
• 0.7% T-amorphol
• 0.5% trans-muurolol
• 0.5% α-muurolene
• 0.4% (Z)-β-ocimene
• 0.2% β-caryophyllene
• 0.2% isoisopulegol
• 0.2% (E)-β-ocimene
• 0.2% 10-epi-γ-eudesmol
• 0.2% α-terpinyl acetate
• 0.1% α-humulene
• 0.1% citronellic acid
• 0.1% decanal
• 0.1% β-bourbonene
• 0.1% (Z)-α-farnesol
• 0.1% myrcene
• 0.1% methyl eugenol
• 0.1% 2,6-dimethyl-5-heptenal
• 0.1% α-copaene
• 0.1% (E)-α-farnesol
• 0.1% sabinene
• 0.1% terpinolene
• 0.1% α-pinene
• 0.1% borneol
• 0.1% α-terpineol
• trace camphene
• trace terpinen-4-ol
• trace 1,8-cineole
• trace neryl acetate
• trace β-phellandrene
• trace tricyclene
• trace β-pinene
• trace δ-3-carene
• trace α-terpinene
• trace δ-elemene
• trace 6-methyl-5-hepten-2-one
• trace (Z)-3-hexenol
• 97.5% total

Source: Carlin et al., 1988.

Physical properties of essential oil

Java citronella oil

• Relative density : 0.880-0.895
• Refractive index : 1.466-1.473
• Optical rotation : -5° to 0°
• Miscibility in ethanol : 1:2 (80%)
• ISO/EOA : ISO 3848 '76

See comments : Physical properties of essential oils (PROSEA)

Authors

C.C. de Guzman & R.A. Reglos

Sources of illustrations

Hsu, C.C., 1975. Taiwan grasses. Taiwan Provincial Education Association, Taipei, Taiwan. p. 664 (inflorescence part, spikelet pair); Purseglove, J.W., 1972. Tropical crops. Monocotyledons 1. Longman Group Limited, London, United Kingdom. Fig. 17, p. 138 (habit). Redrawn and adapted by P. Verheij-Hayes.