Ocimum gratissimum Seeds | Clove Basil

Clove Basil (Ocimum gratissimum) with broad aromatic leaves and tall spikes of white flowers — Clove Basil (*Ocimum gratissimum*): Lamiaceae, the clove-scented African basil, a woody-based subshrub grown for its eugenol-rich leaves.

LATIN NAME: Ocimum gratissimum

COMMON NAME: Clove Basil

Plant Profile

Clove basil is a woody-based subshrub, one to two metres tall, with square stems, a slightly hairy surface and broad, ovate leaves with toothed margins and a strong, spicy, clove-like scent when bruised. The plant is much larger and more robust than the sweet basil of the kitchen, and in a warm climate it becomes a loose, open bush that flowers for months. The leaves are mid-green, sometimes flushed with purple, and they are held in opposite pairs up the stem.

The flowers are small and white to pale lilac, carried in long, upright spikes that rise above the foliage from summer into autumn, and they are worked constantly by bees and butterflies. The species is native to tropical Africa, Arabia and the Indian subcontinent, and it has naturalised across the tropics, where it grows as a weed of roadsides, disturbed ground and cultivation. It is a short-lived perennial in frost-free climates and is grown as an annual where winters are cold. There are several chemotypes within the species, with essential oils dominated variously by eugenol, thymol or geraniol, and the scent of a plant is the quickest way to tell which one you have.

Science & Biotechnology

The essential oil is the reason the plant is studied. Eugenol is the dominant compound in most African material, often making up more than half of the oil, with thymol, geraniol, linalool and methyl eugenol as the other significant constituents depending on the chemotype and the country of origin. The oil has shown strong antimicrobial activity against bacteria and fungi in laboratory tests, including some drug-resistant strains, and it has been examined as a food preservative and as a surface disinfectant. Thymol chemotypes are of particular interest because thymol is the active principle of thyme oil and has a well-established antiseptic record.

Pharmacological work has looked at the anti-inflammatory, antioxidant, antidiabetic and antidiarrhoeal activity of leaf extracts, mostly in animal models, and at the traditional use of the plant against intestinal parasites. The mosquito-repellent properties of the oil have been tested, with moderate results compared with synthetic repellents, and the plant is burned or hung in houses in parts of Africa for that purpose. A note of caution belongs here: like sweet basil, the plant can accumulate high levels of methyl eugenol in some chemotypes, and methyl eugenol is a genotoxic compound of concern at high doses, which is one reason essential oil supplements should not be taken casually.

Uses & Benefits

In the kitchen the leaves are used as a substitute for clove and basil in soups, stews, rice and fish dishes across West and East Africa, and in parts of Asia they flavour curries and pickles. The flavour is stronger and more medicinal than sweet basil, so a little goes a long way. In traditional medicine the leaf is used as a tea for coughs, stomach upset, diarrhoea and fever, and the crushed leaves are applied to the skin for minor wounds and insect bites. The plant is also grown as a companion and a repellent around the house.

In the garden it is a useful aromatic shrub for a warm climate, giving height, late flowers and a scent that carries across a path. It is a good plant for a herb garden, a pot on a sunny terrace, or the back of a border where its tall flower spikes can be seen. It is tender below about five degrees, so in cool climates it is best grown in a large pot and moved under cover for winter, or raised afresh from seed each year. Pinching the tips keeps it bushy and delays flowering, which improves the leaf crop.

Growing from Seed

Sow the seed on the surface of a moist, free-draining mix in spring, at twenty to twenty-five degrees, and cover very lightly, since light aids germination. It comes up in one to two weeks. Keep the seedlings warm and bright, and prick them out as soon as they can be handled. Water carefully, because damping off is the main risk at this stage.

Plant out after the last frost, into rich, well-drained soil in full sun, allowing fifty centimetres between plants. Water regularly and pinch out the tips every few weeks to encourage branching and to delay flowering. Feed with a liquid fertiliser monthly if the soil is poor. In frost-free climates, cut the plant back hard in late winter to renew it. Cuttings root readily in summer and are the way to keep a particularly good chemotype, since seed produces variable plants.

Our Take

A robust, aromatic herb for a warm garden, with a place in the kitchen and in the medicine cabinet. Grow it from seed each year in cool climates, keep it pinched, and use the leaves fresh.

Herb Seeds