Cymbopogon martini (PROSEA)

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Plant Resources of South-East Asia
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1, base of culm; 2, leafy shoot; 3, part of inflorescence; 4, pair of spikelets.

Cymbopogon martini (Roxb.) J.F. Watson


Protologue: in Atkinson, Gaz. N.W. Prov. India 10: 392 (1832).
Family: Gramineae
Chromosome number: 2n= 20 (diploid, var.sofia), 40 (tetraploid, var.martini)

Synonyms

  • var. martini : Andropogon martini Roxb. (1820), Cymbopogon martini (Roxb.) J.F. Watson var. motia auct., p.p., C. motia Gupta (1970);
  • var. sofia : Andropogon martini Roxb. (1820).

Note: Although the specific epithet was originally published as " martini ", it is often written as " martinii ".

Vernacular names

var. martini :

  • Palmarosa grass, motia, rosha grass (India) (En)
  • Vietnam: sả hoa hồng.

var. sofia :

  • Gingergrass, sofia, russa grass (India) (En).

Origin and geographic distribution

C. martini originates from the Indian subcontinent where wild stands have been exploited since antiquity and still produce an important portion of the essential oil. At the beginning of the 20th Century palmarosa grass was also taken into cultivation in India. In the 1930s palmarosa grass was introduced to Java where it yielded promising quantities of high quality oil. Production in Java grew steadily. It declined sharply during the Second World War, but was resumed on a smaller scale in the 1990s. In addition to India and Java, it is now also grown commercially in Brazil, Guatemala, Honduras, Madagascar and on a smaller scale in other African countries. In most of South-East Asia it is only grown occasionally. Var. sofia is sometimes cultivated in India.

Uses

Two different oils are obtained from C. martini, preferably from the flowering tops: var. martini yields palmarosa oil, confusingly also named East Indian geranium oil, while gingergrass oil is obtained from var. sofia. Palmarosa oil is applied in perfumes for soaps and cosmetics and for flavouring tobacco and liqueurs. It is also an important source of natural geraniol, which is an excellent extender in many floral, rose-like perfume compounds and a starting material for the production of aroma chemicals, notably geranyl esters that have a lasting rose-like aroma. Palmarosa oil is an active component of mosquito repellents. Gingergrass oil was once a popular perfumery material for rose compounds, particularly in soaps, but lost its popularity due to frequent adulteration. It is now mainly applied in the soap and detergent industry in India.

C. martini is also grown extensively to control erosion on erodible hillsides and to stabilize edges of terraces and gullies. In traditional medicine C. martini and its oils are used to treat rheumatism, hair loss, arthritis, lumbago and spasms.

Production and international trade

In India palmarosa oil is mainly produced in Assam, Andhra Pradesh, Madya Pradesh and Maharashtra; gingergrass oil mainly in Andhra Pradesh, Punjab and Tamil Nadu. World production of palmarosa oil was about 55 t in 1984, valued at about 2.5 million US$. Gingergrass oil is of only minor importance, its annual world production being less than 2 t.

Properties

All aboveground parts of C. martini contain essential oil, the oil content of the flowers being higher than that of the stems and leaves. The oil content in high-yielding selections grown under optimum conditions can reach 0.5-1.5%; the average yield from traditional stills, however, is only 0.2-0.3% (both on a fresh weight basis).

Palmarosa oil is a pale yellow or pale olive liquid with a sweet, floral-rosy odour with variable top notes and undertones depending on the quality and age of the oil; notes of rye bread, tea and clary sage have also been reported. Chemically, palmarosa oil consists mainly of geraniol and geranyl acetate and smaller amounts of linalool, farnesol, nerol, α-humulene and terpineols. In soap perfumes palmarosa oil shows great tenacity, much greater than commercial geraniol obtained from other sources, e.g. citronella oil. It blends well with most soap perfume compounds and forms an excellent perfume base with geranium oil and oakmoss absolute. Palmarosa oil from Indonesia has a significantly higher geranyl acetate content than Indian oil. This is due not only to differences in growing conditions, but also to the use of more modern distilleries. In the United States, palmarosa oil is "generally recognized as safe" (GRAS No 2831). Gingergrass oil has a harsher, turpentine-like, somewhat fatty, herbal and cumin-like odour with a rose nuance and woody undertone. The chemical composition of gingergrass oil is characterized by high proportions of limonene, p-mentha-1(7),8-dien-1-ol (trans-isoperillyl alcohol), p-mentha-2,8-dien-1-ol, carveol and carvone.

See also: Composition of essential-oil samples and the Table on standard physical properties.

Palmarosa oil is a strong fungicide. In laboratory tests it was more effective than several synthetic fungicides against 9 pathogenic fungi and yeasts, including Aspergillus spp., Candida albicans, Monilia sitophila and Trichophyton tonsurae.

Adulterations and substitutes

Ninde oil produced from Aeolanthus gamwelliae G. Taylor, a Labiatae shrub, is occasionally used as a substitute for palmarosa oil. It is grown commercially in Malawi. Cymbopogon densiflorus (Steudel) Stapf from Angola produces an essential oil very similar to gingergrass oil, but this oil is not produced commercially. Palmarosa oil has been used as an adulterant of Turkish rose attars. The names "Geranium palmarosa" and "Geranium palmarosa Turkish" were used for the adulterated product. Palmarosa oil is sometimes adulterated with ginger oil, with geraniol obtained from citronella oil and with synthetic geraniol.

Description

  • Perennial, tufted, aromatic grass with numerous erect culms arising from a short, stout, woody rhizome. Culm (stem) terete, up to 2(-3) m tall, smooth, glabrous, lower nodes often swollen.
  • Leaves sheathing; sheath shorter than internode, tightly embracing the culm, striate, auriculate, glabrous, basal ones looser and breaking up into fibres; ligule oblong, 1.5-4 mm long, membrano-chartaceous; blade linear-lanceolate with long filiform tip, up to about 50 cm × 3 cm, cordate at base, often amplexicaul, margins often scabrid, glabrous, lower surface glaucous or pruinose, both surfaces smooth.
  • Inflorescence an erect, narrow, loose to dense, repeatedly branched panicle, up to 30 cm × 5 cm, the primary axis carrying 2-3 branches at each node, each of these ending in a spatheole which carries a peduncle crowned with a pair of racemes; spatheole elliptical-acute when flattened, up to 4 cm long, orange-red, smooth or rough; peduncle filiform, 1-6 mm long; raceme 1.5-2 cm long, consisting of 4-7 pairs of spikelets, 1 of each pair sessile, the other pedicellate, terminated by 1 sessile and 2 pedicellate spikelets; rachis, internodes and pedicels slender, flattened on 1 side, pilose along the margins.
  • Sessile spikelet cylindrical-acute, 3.5-4.5 mm long, glabrous; lower glume shape and size of the spikelet, 2-keeled in upper half, winged on the keels, apex emarginate; upper glume boat-shaped, as long as the spikelet, with a broad wing on the keel; lower floret reduced to empty lemma; upper floret hermaphrodite, with 3 mm long, narrow lemma bearing a 12-18 mm long awn, palea absent, 3 stamens, 2 styles with plumose stigma.
  • Pedicellate spikelet elliptical-acute, 3.5-4 mm long, male, lower glume many-veined, upper glume 3-veined, florets reduced to a hyaline oblong scale wrapped round 3 stamens.
  • Fruit a cylindrical to subglobose caryopsis, with basal hilum; the fruiting panicle often turns bright red at maturity.

Growth and development

C. martini grows naturally in round clumps or tussocks. In var. martini the clumps remain separate, but they grow much closer together in var. sofia, sometimes forming continuous closed stands of several ha. C. martini is strongly cross-pollinated and wild stands are highly variable. Oil yield and geraniol content are highest under long days. Flowering in India occurs in November-December. The colour of the inflorescence changes from greenish before anthesis to red.

Other botanical information

Traditionally two forms of C. martini, motia and sofia, were distinguished in India. Much later these were given the status of botanical varieties: var. martini, which is palmarosa grass or motia and var. sofia Bruno, which is gingergrass or sofia. They are almost indistinguishable morphologically. Reported differences include:

  • var. martini : diploid; the upper surface of the culm leaves make a right or obtuse angle with culm; few radical leaves present; it grows in scattered patches; habitat dry and sunny; oil with a floral rosy smell and geraniol content up to 95%.
  • var. sofia : tetraploid; the upper surface of culm leaves makes an acute angle with the culm; many radical leaves present; the grass grows in dense masses; habitat wetter and less sunny; oil with a turpentine-like odour and geraniol content up to 65%.

A practical method to distinguish the 2 varieties is to move an inflorescence leaf between the fingers from base to tip: var. sofia feels rough and sticky, var. martini smooth and clean. Spontaneous hybrids are common where their natural habitats overlap. Several cultivars of var. martini yielding high quality oil have been developed.

C. caesius (Nees ex Hook. & Arnott) Stapf from Madras (India) slightly resembles C. martini and produces an oil similar to gingergrass, but is hardly exploited. It is glaucous with narrow leaves rounded at the base and the panicle remains yellow-green at maturity.

Ecology

C. martini occurs naturally and in cultivation in India from 12-32°N and is also grown commercially from about 5°S in Java and the Seychelles to 20°S in Madagascar. It is cultivated from 150-800(-1200) m altitude. Although under natural conditions it is often found on hillsides with an annual rainfall below 600 mm, it requires about 750 mm annual rainfall for a reasonable single harvest. If it is to be harvested several times per year, it requires at least 1500 mm annual rainfall and supplementary irrigation during periods of drought. C. martini prefers warm and sunny conditions with average daily temperatures of 20-25°C; temperatures of 25-30°C for extended periods can significantly reduce yields and suppress flowering. Frost causes damage at all growth stages and at higher elevations aboveground plant parts may die back during the cool season. Even slight frost at harvesting can be devastating and may reduce yields by half. Long days seem to favour oil production, both in quantity and in geraniol content.

In its natural habitat C. martini grows on poor, often slightly alkaline soils (pH 7.5-8.5) of sandy-loamy to loamy texture. Soils rich in organic matter and nitrogen are reported to yield high quality oil. In Orissa, India it is found on slightly saline soils. In cultivation, fertile well-drained soils of pH 6-7 are considered optimum. On alkaline soils (pH 8.5 or higher) growth and yields are reduced, but oil quality is not affected. Palmarosa grass does not tolerate acid soils or waterlogging. Gingergrass is more tolerant of prolonged periods of heavy rain that saturate the soil and also of imperfectly drained soils.

Propagation and planting

C. martini is generally propagated by seed. Propagation by offshoots and cuttings is also possible, but there are indications that seedlings yield more herbage and oil. Care should be taken to use pure seed of var. martini, in particular in India and Pakistan where natural stands often are mixtures of var. martini and var. sofia. Seed is sown in nursery beds; 2.5 kg of clean seed is used for 100 m2nursery, providing enough seedlings for a field of 1 ha. The tiny seeds are often mixed with fine sand to obtain even distribution, and the mixture is then beaten to detach the glumes and improve germination. Healthy seed germinates 10-20 days after sowing and seedlings are ready for transplanting in 6-8 weeks when 15-20 cm tall. In India, planting is done on flat land or on ridges. When irrigated, beds with several rows per bed are also suitable. As C. martini grows vigorously, seedlings should be planted singly. On small farms, spacings of 80-90 cm × 80-90 cm are common; for larger plantations where adequate amounts of fertilizer and irrigation are applied 30 cm × 30-45 cm or twin rows with a wider spacing between alternate rows is recommended. Planting is done after irrigation or after the onset of the monsoon. Planting at the end of the rainy season results in slow crop growth but less competition from weeds. Its vigorous growth makes C. martini unsuitable for use in intercropping systems. However, the Indian Forest Department recommends planting it in forest plantations as a cash crop, since it is unpalatable to livestock and discourages grazing in young plantations.

Husbandry

New plantations of C. martini should be weeded several times, but an established crop quickly smothers most weeds after being harvested. Fertilizer requirements are not well documented. A crop producing 11 t dry matter in India removed 32 kg N, 7.5 kg P, 21 kg K, 35 kg Ca, 21 kg Mg and 21 kg S. Yields tend to decline rapidly if no fertilizer is applied: in India herbage yields fell from 11.5 t/ha in the first and second year to 8.4 t/ha in the 4th year and 4.1 t/ha in the 7th year, while oil content fell from 1.5 g to 0.8 g per 100 g fresh matter. An annual application of 40 kg N, preferably in a compound NPK fertilizer (40-40-20 or 40-20-20), is a general recommendation, but is probably the minimum for sustained production. Var. martini has a life span in cultivation of 10-15 years, but many plantations become unprofitable after 6-7 years.

Diseases and pests

A blight caused by Ellisiella caudata (Curvularia andropogonis) may cause severe damage in C. martini during the rainy season throughout India. It causes greyish-brown spots on the leaves that coalesce to form large lesions. Colletotrichum caudatum leaf spot may also affect the crop. Serious pests are not known for C. martini.

Harvesting

C. martini should be harvested when plants are flowering, the oil content of the flowers is highest after opening and drops dramatically after flowering. The harvesting period can be extended by planting early- and late-flowering strains. The first harvest can be taken about 6 months after planting; the number of subsequent harvests per year depends on temperature and water availability. In northern India, where frost is common, only 1 harvest per year is possible, but irrigated crops in Java can produce up to 4 harvests per year. The time of harvesting affects oil yield and quality. Harvesting during the rainy season gives high herbage and oil yields, but low geraniol content, while during the dry season herbage and oil yield are lower and geraniol content higher. Harvesting is done by hand or mechanically. Hand harvesting requires about 6 man-days per ha. Mechanical harvesters that cut, chop and load the crop for direct transport to the still are available and can harvest about 1 ha per hour. The height of cutting is generally 20 cm above the ground. Cutting high leaves a substantial stubble, so reducing the cost of harvesting and distillation, but cutting low stimulates regrowth of the crop.

Handling after harvest

After harvesting, the crop is often spread out in the field for 4-6 hours to lose moisture. It can then be kept in a shady cool place for several days without much loss of oil. Poor storage conditions, however, can seriously reduce the oil content. Grass from wild stands in India is stored for up to 3 weeks before being distilled. In India, traditional stills are widely used, many of them employing a water distillation process. In Java and Madagascar, however, modern steam distillation equipment is employed.

Yield

Well managed plantations of C. martini var. martini in India produce annual herbage yields of 10-15 t/ha, giving 50-100 kg oil. Improved cultivars may yield up to 25 t/ha of herbage producing 150 kg oil. Little is known about yields in other countries.

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

Most of the little breeding work done on C. martini is carried out in India. The first high-yielding selections were made by the Amravati Forest Division in Maharashtra. Many commercial cultivars have been developed from these selections. From germplasm collected in Madhya Pradesh and Maharashtra selection IW-31245 was chosen to be released as a cultivar. It has a high yield potential (10-11 t/ha), high oil yield (about 100 kg) with a high geraniol content (90%). Other cultivars released in India are "RH-49" and "Trishna". Breeding work in India aims at strong tillering, large inflorescences, thin culm, long leaves, a high herbage and oil yield and a high geraniol content.

Prospects

Palmarosa oil has gradually lost importance in the world market, being replaced by low-cost synthetic or natural geraniol. The natural oil is still preferred in high quality perfumes, however, especially in the Middle East. Gingergrass oil will probably remain mainly of local importance only in India. Production of palmarosa oil in South-East Asia is very feasible and will be of interest as soon as world prices for natural geraniol rise.

Literature

  • Boelens, M.H., 1994. Sensory and chemical evaluation of tropical grass oils. Perfumer and Flavorist 19: 29-45.
  • Duke, J.A. & duCellier, J.L., 1993. CRC handbook of alternative cash crops. CRC Press Inc., Boca Raton, Florida, United States. pp. 214-215.
  • Gupta, R., Pareek, S.K. & Maheshwari, M.L., 1995. Palmarosa. In: Chadha, K.L. & Gupta, R. (Editors): Advances in Horticulture. Vol. 11. Medicinal and aromatic plants. Malhotra Publishing House, New Delhi, India. pp. 735-749.
  • 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. 103-117.

Composition of essential-oil of Palmarosa oil

  • 75.0% geraniol
  • 12.5% geranyl acetate
  • 2.4% linalool
  • 1.3% β-caryophyllene
  • 1.3% geranyl formate
  • 1.3% geranyl butyrate
  • 1.0% geranyl octanoate
  • 0.5% limonene
  • 0.5% caryophyllene oxide
  • 0.4% prenyl isovalerate
  • 0.3% pentyl hexanoate
  • 0.3% 6,7-geranylepoxide
  • 0.3% geranyl hexanoate
  • 0.2% neryl formate
  • 0.2% prenyl hexanoate
  • 0.1% nerol
  • 0.1% limonen-10-yl-acetate
  • 0.1% 2,3-geranylepoxide
  • 0.1% α-pinene
  • 0.1% myrcene
  • 0.1% γ-terpinene
  • 0.1% geranial
  • 0.1% 1,8-cineole
  • 0.1% 1-hexanol
  • 0.1% geranyl 3-methylbutyrate
  • 0.1% para-mentha-1,8(10)-dien-9-ol
  • 0.1% prenyl octanoate
  • 98.1% total
Source: Sethi et al., 1989.


Physical properties of essential oil

palmarosa oil

  • Relative density : 0.880-0.894
  • Refractive index : 1.471-1.478
  • Optical rotation : +1.4° to +3°
  • Miscibility in ethanol : 1:2 (70%)
  • ISO/EOA : ISO 4727 '88

See comments : Physical properties of essential oils (PROSEA)

Sources of illustrations

Matthew, K.M., 1982. Illustrations on the flora of the Tamilnadu Carnatic. The Rapinat Herbarium, St. Joseph's College, Tiruchirapalli, India. Fig. 836 & 837. Redrawn and adapted by P. Verheij-Hayes.

Authors

C.C de Guzman & R.A. Reglos