Coleus amboinicus Lour.

Taxonomic Classification and Height

Coleus amboinicus Lour. is a member of the mint family Lamiaceae, growing up to 1 meter (3.3 feet) tall.

Stem Characteristics

Its stems are fleshy, 30–90 cm (12–35 in) long, and covered in either long rigid hairs (hispidly villous) or dense, short erect soft hairs (tomentose); older stems become smooth (glabrescent).

Leaf Dimensions and Basic Shape

The leaves are 5–7 cm (2.0–2.8 in) by 4–6 cm (1.6–2.4 in), fleshy, simple (undivided), broad, and ovate (egg/oval-shaped with a tapering tip).

Leaf Margin Structure

Except at the base, leaf margins are coarsely crenate to dentate-crenate.

Leaf Hair Covering

Leaves are thickly covered in hairs (pubescent), with the most numerous glandular hairs on the lower surface that give a frosted appearance.

Leaf Petiole Length

Leaf petioles measure 2–4.5 cm (0.79–1.77 in) long.

Leaf Aroma and Taste

The leaf aroma is a pungent combination of oregano, thyme, and turpentine, and the leaf taste is similar to oregano with a sharp mint-like flavor.

Flower Arrangement and Color

Flowers are shortly pedicelled (borne on short stems), pale purplish, and arranged in dense 10-20 (or more) flowered whorled cymes.

Cyme and Raceme Structure

These cymes are spaced at distant intervals along a long, slender, spike-like raceme.

Raceme Rachis Characteristics

The raceme rachis is 10–20 cm (3.9–7.9 in) long, fleshy, and pubescent.

Bract Features

Bracts are broadly ovate, 3–4 cm (1.2–1.6 in) long, and acute-tipped.

Calyx Structure

The calyx is campanulate (bell-shaped), 2–4 mm (0.079–0.157 in) long, hirsute and glandular, with five subequal teeth: the upper tooth is broadly ovate-oblong, obtuse with an abrupt acute point, while the lateral and lower teeth are acute.

Corolla Shape and Size

The corolla is blue, curved and declinate, 8–12 mm (0.31–0.47 in) long, with a 3–4 mm (0.12–0.16 in) long tube that widens into a trumpet shape.

Corolla Limb Structure

The corolla limb is two-lipped: the upper lip is short, erect, and finely pubescent, while the lower lip is long and concave.

Stamen and Style Structure

Filaments are fused below into a tube that surrounds the style.

Seed Characteristics

The seeds (nutlets) are smooth, pale-brown, roundish and flattened, approximately 0.7 by 0.5 mm (0.028 by 0.020 in) in size.

Native Distribution

This species is native to Southern and Eastern Africa (ranging from KwaZulu-Natal, South Africa and Eswatini to Angola and Mozambique, and north to Kenya and Tanzania), the Arabian Peninsula, and India.

Habitat and Elevation

It grows in woodland or coastal bush, on rocky slopes, and on loamy or sandy flats at low elevations.

Introduction History and Common Name

It was later introduced to Europe, then brought from Spain to the Americas, which gave it the common name Spanish thyme.

Culinary Use as Flavor Substitute

The strongly flavored leaves of this herb are used as an oregano substitute to mask strong odors and flavors of fish, mutton, and goat.

South Asian Culinary Uses

Leaves may be batter-fried to make pakodas, or added to rasam.

Caribbean Culinary Use

In the Caribbean, leaves are commonly used to season meats for their pungent aroma.

Non-culinary Leaf Uses and Ornamental Value

Fresh leaves are used to scent laundry and hair, and the plant is also grown as an ornamental.

Common Cultivation Methods

Coleus amboinicus is a fast-growing plant commonly cultivated in gardens and grown indoors in pots.

Propagation Methods

It can be propagated by stem cuttings, and can also be grown from seed.

Dry Climate Cultivation Requirements

In dry climates, it grows easily in well-drained soil in a semi-shaded position.

Hardiness and Warm Climate Suitability

It is frost tender, suited to USDA hardiness zones 10–11, and grows well in subtropical and tropical locations.

Cool Climate Cultivation Tips

In cooler climates, it can be grown successfully in a pot if brought indoors or moved to a warm, sheltered location over winter.

Humid Tropical Cultivation Requirements

In humid tropical locations such as Hawaii, the plant requires full sun.

Harvesting Guidelines

It can be harvested throughout the growing season for use fresh, dried, or frozen.