Ocimum gratissimum is an erect, much-branched, aromatic shrub growing 50 - 300cm tall.
The plant is often cultivated, mainly in the tropics, where it provides a range of culinary and medicinal applications, and is an effective insect repellent. It yields an essential oil, for which it is grown on a commercial scale, the oil being exported to many countries. The leaves are sometimes sold in local markets in Africa.

Known Hazards

None known

Habitat

Along lake shores, in savannah vegetation, in submontane forest, and disturbed land
; at elevations from sea level to 2,382 metres in west Africa.

Cultivation Status

Cultivated

Cultivation Details

Prefers a rich, light, well-drained to dry soil and a position in full sun.
All parts of the plant are strongly scented.
The optimum harvesting time for distillation of the essential oil is when 3 branches per plant, or 75% of the branches, are flowering. In northern Vietnam 2 - 3 cuts can be obtained in an average year, 4 - 5 cuts per year in the south. In Vietnam, Ocimum gratissimum remains productive for 5 - 10 years.
In India, yields of 70 - 75 tonnes per hectare green herbage, producing 400 litres of essential oil in 2 years have been obtained experimentally.
In Thailand harvesting every 10 - 12 days resulted in an annual green herbage yield of only 13 tonnes per hectare, and an oil yield of nearly 200 litres.

Edible Uses

Leaves - cooked and eaten as a potherb, either on its own or sometimes combined with other leaves and the seeds of watermelon (Citrullus lanatus).
The leaves are also used as a flavouring with other foods.
A favoured food in west Africa.
There are both clove and thyme-scented forms.
The variety viride has leaves with the flavour of lemon thyme that can be used in salads and as a seasoning as well as to make herb teas.
The leaves are infused to make a tea.
Seeds - sometimes eaten in India.

Medicinal

Clove basil is an aromatic, stimulant, antispasmodic, antiseptic and diaphoretic herb that repels insects, expels internal parasites and lowers fevers.
The leaves and stems are used internally in the treatment of a range of conditions including colds and influenza, especially chest colds; fevers, sunstroke, headaches, impotence, flatulence, diarrhoea, dysentery, post-partum problems, and worms in children.
Applied externally, the leaves are used to treat rheumatism and lumbago.
An essential oil obtained from the leaf has shown marked antibacterial activity.

Agroforestry Uses

The plant is sometimes grown as a hedge.

Other Uses

The fresh above-ground parts of the plant contain 0.8 - 1.2% essential oil. The chemical composition of this oil is variable and at least 6 chemotypes have been reported, characterized by the main component of the particular essential oil. These are: -
Eugenol. This is the most important economically. It is a brownish-yellow to pale yellow liquid with a powerful, warm-spicy and aromatic odour, reminiscent of clove oil, but with a sweet-woody, almost floral top note. The dry-out is more bitter than that of clove oil. Analysis of a sample of an essential oil of the eugenol type from Vietnam indicated that the main component was eugenol (71%) with small amounts of D-germacrene and (Z)-beta-ocimene. In a sample from southern China the eugenol content was as much as 95%. Samples from Madagascar had eugenol contents of 40-90%, with very variable other components.
Thymol. This used to be important, but most thymol is now produced synthetically, while natural thymol is mostly obtained from Thymus vulgaris or Trachyspermum ammi. The thymol-type oil is a dark yellow to orange-yellow or brownish liquid with a medicinal-spicy, warm and somewhat herb-like odour. Its flavour is warm, slightly astringent and burning, and has a sweet medicinal aftertaste. Analysis of several samples of essential oils from O. Gratissimum from Central and West Africa rich in thymol indicated that their main constituents were thymol, gamma-terpinene, p-cymene and eugenol. The concrete obtained by solvent extraction is much richer in thymol than the distilled oil.
Citral. The citral type, reported from Iran, Pakistan and India, is rich in citral (67%) and geraniol (26%).
Ethyl cinnamate.
Geraniol.
Linalool.
The essential oil in the plant is used in perfumery.
The plant repels insects.
It is grown specifically to repel mosquitoes, whilst the essential oil is used in repellent formulae.
The peeled twigs are used as chewing sticks in order to clean the teeth and maintain oral hygiene.

Propagation

Seed - germination rates can be less than 10%.
Sow in a nursery seedbed and only just cover the seed. Germination is usually free and quick, prick out the seedlings into individual pots when they are large enough to handle and plant out when large enough.
Cuttings take about 28 days to root.