Agroforestree Database

Local names:
 English (wild basil,tree basil,East Indian basil,clove basil), French (menthe gabonaise), Indonesian (ruku-ruku rimba), Malay (ruku-ruku hitam), Thai (horapha-chang), Vietnamese ([es] l[as] l[ows]n)

Ocimum gratissimum is an aromatic, perennial herb, 1-3 m tall; stem erect, round-quadrangular, much branched, glabrous or pubescent, woody at the base, often with epidermis peeling in strips. 

Leaves opposite; petiole 2-4.5 cm long, slender, pubescent; blade elliptical to ovate, 1.5-16 cm x 1-8.5 cm, membranaceous, sometimes glandular punctate, base cuneate, entire, margin elsewhere coarsely crenate-serrate, apex acute, puberulent or pubescent. 

Inflorescence a verticillaster, arranged in a terminal, simple or branched raceme 5-30 cm long; rachis lax, softly pubescent; bracts sessile, ovate, 3-12 mm x 1-7 mm, acuminate, caducous; pedicel 1-4 mm long, spreading or ascending, slightly curved; flowers in 6-10-flowered verticillasters, small, hermaphrodite; calyx 2-lipped, 2-3 mm long, in fruit 5-6 mm, pubescent, upper lip rounded and recurved, reflexed in fruit, lower lip with 4, narrow, pointed teeth, central pair of teeth minute and much shorter than the upper lip; corolla campanulate, 3.5-5 mm long, 2-lipped, greenish-white, pubescent outside, upper lip truncate, 4-fid, lower lip longer, declinate, flat, entire; stamens 4, declinate, in 2 pairs, inserted on the corolla tube, filaments distinctly exserted, upper pair with a bearded tooth at the base; ovary superior, consisting of 2 carpels, each 2-celled, style 2-fid. 

Fruit consisting of 4, dry, 1-seeded nutlets enclosed in the persistent calyx (the lower lip closing the mouth of the fruiting calyx); nutlet subglobose, 1.5 mm long, rugose, brown; outer pericarp not becoming mucilaginous in water.

O. gratissimum is a variable polymorphic complex species, often subdivided into subspecies, varieties and formas, mainly based on differences in chemical content, the morphology of the fruiting calyx, and on different degrees of hairiness, but the variation forms a continuum. Sometimes O. gratissimum (existing chromosome counts: 2n = 40, 48, 64), O. suave (2n = 32, 48, 64) and O. viride (2n = 38, 40) (here treated as one complex species O. gratissimum) are considered as three different species. Although more research is needed it seems certain that those three taxa are closely related and have 10 homologous chromosomes in common. Crosses between O. gratissimum and O. viride resulted in partially fertile F1 hybrids. Variability is greatest in Africa and India. In Java, 2 chemotypes exist, the eugenol and the thymol type, respectively described as O. gratissimum L. forma caryophyllatum Backer and forma graveolens Backer. Forma caryophyllatum is characterized by: leaves clove-scented when bruised, upper side short-haired, lower side densely gland-dotted, bracts 4-6 mm long, much longer than wide, lower lip of corolla not flushed with violet; and forma graveolens by: leaves strongly odoriferous but not clove-scented when bruised, upper surface covered with minute hairs, bracts 2-4 mm long, about as long as wide, lower lip of corolla flushed violet inside. Most Ocimum species contain essential oil but are primarily used as vegetable (e.g. hoary basil, O. americanum L.), as spice (e.g. sweet basil, O. basilicum L.), or as vegetable and medicine (e.g. sacred or holy basil, O. tenuiflorum L.).

Ecology

In its native area O. gratissimum occurs from sea-level up to 1500 m altitude in coastal scrub, along lake shores, in savanna vegetation, in submontane forest, and disturbed land. In South-East Asia it is not frequently found in open locations like roadsides and clearings, but more often cultivated as a hedge plant, up to about 300 m altitude.

Native range

Tree management

The time for transplanting seedlings into the field in the delta of the Hong River in northern Vietnam is February-March, in southern Vietnam from May-August. Plants are spaced at about 40 cm x 50 cm. 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, O. gratissimum remains productive for 5-10 years.

In India, yields of 70-75 t/ha green herbage of O. gratissimum producing 400 l 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 t/ha and an oil yield of nearly 200 l.

In its native area O. gratissimum occurs from sea-level up to 1500 m altitude in coastal scrub, along lake shores, in savanna vegetation, in submontane forest, and disturbed land. In South-East Asia it is not frequently found in open locations like roadsides and clearings, but more often cultivated as a hedge plant, up to about 300 m altitude.

O. gratissimum is propagated by seed or cuttings. In a growth trial in Colombia, germination of O. gratissimum was very poor (<10%); cuttings took 28 days to take root.

Poison: The essential oil is also an important insect repellent.

Medicine: The whole plant and the essential oil have many applications in traditional medicine, especially in Africa and India. Preparations from the whole plant are used as stomachic and in treating sunstroke, headache and influenza. The seeds have laxative properties and are prescribed against gonorrhoea. The essential oil is applied against fever, inflammations of the throat, ears or eyes, stomach pain, diarrhoea and skin diseases. It is being tested as an antibiotic.

O. gratissimum is also cultivated as a hedge plant.

Essential oils: O. gratissimum is grown for the essential oil in its leaves and stems. Eugenol and to a lesser extent thymol extracted from the oil are substitutes for clove oil and thyme oil.