Palmaroza

Cymbopogon martinii is a species of grass in the genus Cymbopogon, native to India and Indochina but widely cultivated in many places for its aromatic oil. It is best known by the common name palmarosa, meaning palm rose, because it smells sweet and rose-like. The grass grows fairly tall, from 1.3 to 3 m in height, with a pale green color and a strong thin stem. It grows slowly, taking three months to flower, and can be harvested once it has flowered. Flowering in India occurs in November-December.

Two forms of the grass, motia and sofia, were traditionally distinguished in India and were much later given the status of botanical varieties. Var. martini is palmarosa grass or motia, and var. sofia is gingergrass or sofia. The two varieties are almost indistinguishable morphologically. The oil of var. martini has a geraniol content up to 95%, while the oil of var. sofia has a turpentine-like odour and a geraniol content up to 65%. A practical way to tell the varieties apart 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.

Palmarosa oil consists mainly of geraniol and geranyl acetate, with smaller amounts of linalool, farnesol, nerol, humulene and terpineols. Geraniol is a monoterpenoid and an alcohol, and a primary component of palmarosa oil. Geraniol has a molar mass of 154.253 g/mol and a boiling point of 230 °C. Geraniol has low solubility in water but is soluble in common organic solvents. In one analysed sample, geraniol made up 82.83% of the volatile fraction and geranyl acetate 7.21%. In another analysis, the leaf oil contained 76.6% geraniol and 15.2% geranyl acetate, and the root oil 87.9% geraniol and 4.4% geranyl acetate. Palmarosa oil from Indonesia has a significantly higher geranyl acetate content than Indian oil. The difference is due not only to growing conditions but also to the use of more modern distilleries. Oil yield and geraniol content are highest under long days.

India is the principal producer and exporter of palmarosa oil. In India it is mainly produced in Assam, Andhra Pradesh, Madhya Pradesh and Maharashtra. Gingergrass oil is of only minor importance, its annual world production being less than 2 t. Palmarosa can be harvested three to four times per year. Seed is sown in nursery beds, and seedlings are ready for transplanting in 6-8 weeks when 15-20 cm tall. Palmarosa grass does not tolerate acid soils or waterlogging. Well managed plantations of var. martini in India produce annual herbage yields of 10-15 t/ha, giving 50-100 kg oil. Var. martini has a life span in cultivation of 10-15 years, but many plantations become unprofitable after 6-7 years.

Palmarosa oil may be an effective insect repellent when applied to stored grain and beans. Palmarosa oil is also an antifungal that fights against Aspergillus niger, Chaetomium globosum and Penicillium funiculosum. In traditional medicine the plant and its oils are used to treat rheumatism, hair loss, arthritis, lumbago and spasms. In the United States, palmarosa oil is generally recognized as safe.

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