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Lemongrass is a tropical perennial grass that yields an aromatic oil containing 70-90% Citral. The name Lemongrass has been given to this crop because of the strong lemon-like odour of the plant that is attributed to the high Citral content present in the leaves. Lemongrass oil is popularly known as Cochin oil in world trade as 90% of the world’s supply comes from Cochin port. Kerala has monopoly in the production of Lemongrass oil. One of the most popular essential oils, it is widely used for the isolation of Citral that can be converted into ionones with the odour of violets. They are used in flavors, cosmetics and perfumes. ß-ionone is used for the commercial synthesis of Vitamin A. In some Far Eastern countries like Java, Japan, China and India, the leaves are used for flavouring foods, drinks like tea and for scenting bathwater. The oil is used as a repellent against flies and mosquitoes. The spent grass is an excellent fuel. It is also used as manure, mulch and forms raw material for the production of silage, mushroom and paperboards. The crop is often cultivated along the bunds as live mulch. The well ramified root system of the plant helps in soil and water conservation.
There are three types of lemongrass that are widely known, viz, East Indian, West Indian and Jammu Lemongrass. East Indian Lemongrass is the genuine and commercial variant.
Lemongrass belongs to the family Gramineae (Poaceae) and the genus Cymbopogon. Three species are generally found.
Cymbopogon flexuous – It is known as East Indian, Cochin or Malabar grass. A tufted robust perennial grass, 2 m tall, it flowers freely and has linear leaves that are lanceolate typically 125×1.7 cms. Panicles are very large, drooping, lax, greyish-green, sometimes with a purplish tinge, with the raceme pairs in dense masses, 100-135 cms long, slightly hairy, lower glumes of the sessile spikelets 3-4 and 4-5 mm long, 1 mm wide with 1-3 definite or obscure intracranial nerves, shallowly concave with 1-2 depressions.
Under this species, two varieties are identified based on the stem colour.
a) C. flexuosus var. flexuosus – The Red grass, locally known as ‘’Chumannapullu” is identified by its stem, which is reddish or purplish in colour. It is recognized as authentic lemongrass and is commercially cultivated. The oil yield is poor but the Citral content of the oil is high (75-90%).
b) C. flexuosus var. albescens – The white grass, locally known as “Vellapullu”, is characterized by the white colour of the stem. The plant is typically found in the wild. The oil retrieved is poor in solubility. The oil yield though high is poor in citral content (60-75%).
Cymbopogon citrates – It is known as West Indian or American lemongrass. C. citratus is a stemless perennial grass with numerous stiff tillers arising from short rhizomatous rootstock, making large tussocks. It seldom flowers in cultivation. Leaf blade is typically narrow, linear, glaucous, drooping, about 50-100 x 0.5-1.5 cms with scabrous margins. Ligule truncate, 0.2-0.8 cms long. Inflorescence is rarely produced, a large loose panicle; spathe bracts long and narrow, sessile spikelets, awnless and linear-lanceolate.
Cymbopogon pendulus – It is known as Jammu Lemongrass. It is white stemmed and dwarf-like in stature. The plant is frost resistant and typically grows in the Sub-Himalayan areas of Northern India.
Lemongrass requires a warm humid climate with plenty of sunshine and rainfall ranging from 2500-3000 mm uniformly distributed over the year. The preferred average temperature is 23-30 degree Celsius. The plant is hardy and tolerant to drought. It is also well suited for rainfed agriculture. It grows well at altitudes between 100-1200 m above MSL. While it is generally grown on poor soil along hill slopes, it flourishes on a wide variety of soils ranging from rich loam to poor laterite. The grass grows best on well drained sandy loam soil.It is propagated through seeds and root divisions or slips. Clonal propagation is preferred as seed propagation leads to considerable genetic heterogeneity resulting in gradual deterioration of yield and oil quality.
Grass is harvested when each individual tiller has 4-5 fully opened leaves. The plants are cut about 10-20 cms above ground level with sickles. The first harvest is obtained after 4-5 months of transplanting.
Crops should not be allowed to produce inflorescence as it adversely affects the growth and development of plants for subsequent harvests.
The harvesting season begins in May and continues till the end of January. Sunny days are ideal, since cloudy and misty conditions tend to depress the leaf oil content.
Grass is harvested at an interval of 60-90 days. If the harvesting interval is below 60 days, the oil quality will be poor. Under normal conditions, 2-3 harvests are possible during the first year of planting and 3-4 in subsequent years.
Herbage yield is usually 3-4 tons/acre per harvest.
Average oil yield is 50-70 kg/acre/year. In the second and subsequent years, 80-100 kg oil/acre may be produced with good management and use of recommended variety.
On an average the oil recovery is 0.2-0.4% and the oil yield is 100-125 kg/ha/year. Typically, the recovery of oil is lower in rainy seasons (June – August).
For effective running of 500 Lt. capacity steam distillation unit, herbage from 20 ac. or 8 Ha. area is required.