Common name: Java citronella

Citronella Grass is cultivated for the essential oil in its leaves, mainly for use by the pharmaceutical, fragrance and cosmetic industries. 

There are two known species of citronella grass, Java citronella which is described here, and Ceylon citronella (Cymbopogon nardus) which produces an inferior type of citronella oil. Both species are believed to have originated from humid tropical lowland areas extending from southern India and Sri Lanka to Southeast Asia.

It is a clumping grass 1.8 m (6 ft) or more in height, made up of erect stems sprouting from underground rhizomes. The closely arranged stems have a leaf sheath at the base, coloured either purple or yellow depending on the variety, and these hold above them long, green sword-shaped leaves that droop at the ends.

The flowers are small and insignificant, borne on a tall, erect and much-branched flowering spike coming into bloom at the end of the rainy season, but rarely produce viable seed.

Use

The leaves on steam distillation yield a pale yellow, citrus-scented essential oil traded as 'Java citronella', which consists mainly of citronellal, citronellol and geraniol. It is widely used as a fragrance in perfumes, soaps and cleaning and disinfecting products, as well as insect repellent formulations, on account of its citronella content.

Health use

Citronella oil has shown good antifungal and antibacterial activity in laboratory tests, in some cases as good as penicillin for certain types of gram-positive bacteria.

Climate

Grows naturally and develops a high oil content in humid tropical climates, generally frost-free areas with annual lows of 17 to 25°C, average annual highs of 28 to 35°C, annual rainfall of 1400 to 4000 mm and a dry season of 4 months or less.

Growing

New plants are started from divisions, made by dividing mature clumps into smaller pieces suitable for planting. The optimal planting time is at the start of the rainy season, when there is sufficient moisture in the soil for the roots to start growing and establish.

It performs best on free-draining loam and sand soils of a moderately acid to alkaline nature, generally with a pH of 5.5 to 7.8, and on sites with full to partial sun exposure. It has poor tolerance to drought and clayey, slow-draining or waterlogged soils.

The leaves are ready to be harvested about nine months after planting and are repeat-harvested every three months after that over the productive life of the plant, which can range from four to nine years depending on the growing conditions. The leaves are cut from the plant starting about 50 cm above the ground and are then dried in the sun for a brief period, to reduce their moisture content before distillation, which is done within twenty-four hours of harvesting.

Yields range from 15,000 to 20,000 kilograms of fresh leaves per hectare per year, and with an average oil content of 1% yields 150 to 200 kilograms of oil, or the equivalent of 134 to 178 lbs per acre. The oil is highly volatile and to prevent loss of aroma is stored in sealed, air-tight containers away from sunlight.

Problem features

It is unlikely to become a weed or invasive species, due to its habit of producing infertile seed.

Citronella oil is a mild irritant to the skin and is reported to cause dermatitis in some people.

Books

• Brady, G. S. & Clauser, H. R & Vaccari, J. A. 2002, Materials handbook : an encyclopedia for managers, technical professionals, purchasing and production managers, technicians and supervisors, 15th ed., McGraw-Hill, New York

• Debboun, M. & Frances, S. P. & Strickman, D. 2006, Insect repellents : principles, methods, and uses, CRC Press, Boca Raton, Florida

• Farooqi, A. A. & Sreeramu, B. S. 2004, Cultivation of medicinal and aromatic crops, Hyderabad University Press, Hyderabad

• Fellows, P. 1997, Traditional foods : processing for profit, Intermediate Technology, Technical Centre for Agricultural and Rural Co-operation, London

• Guenther, E. & Althausen, D. 1948 to 1952, The essential oils (6 volumes), Van Nostrand Publishing, New York

• Hill, A. F. 1952, Economic botany : a textbook of useful plants and plant products, 2nd ed, McGraw-Hill, New York

• Khan, I. A. & Abourashed, E. A. 2010, Leung's encyclopedia of common natural ingredients : used in food, drugs and cosmetics, 3rd edition, Wiley Publishing, Hoboken, New Jersey

• Macmillan, H. F. 1943, Tropical planting and gardening : with special reference to Ceylon, 5th ed, Macmillan Publishing, London

• Oyen, L. P. A. & Nguyen X. D. 1999, Plant Resources of South-East Asia (PROSEA) 19 : Essential-oil plants, Backhuys Publishers, Leiden