Ocimum americanum L.
Family
Labiatae
Synonyms
Ocimum africanum Lour., Ocimum canum Sims, Ocimum brachiatum Blume.
Vernacular Names
| Malaysia | Selaseh, kemangi, ruku-ruku. |
| English | Hoary basil, American basil. |
| Indonesia | Kemangi, serawung, selasih putih. |
| Thailand | Maenglak. |
| Vietnam | Rau h[us]ng. |
Geographical Distributions
Ocimum americanum occurs wild and cultivated throughout tropical Africa and tropical Asia. Its exact origin is unknown. In Southeast Asia, it has been reported from the continental parts of Indonesia and Papua New Guinea. Its occurrence in the Philippines is doubtful. It has also been introduced into tropical America and some islands of the West Indies.
Description
O. americanum is an erect, much-branched, annual, aromatic herb that can reach up to 0.3-1 m tall. The stem and branches are quadrangular, yellowish-green and densely white-pilose in the young parts but less when older.
The leaves are simple, decussate and with petiolate. The petiole is up to 2.5 cm long. The leaf-blade is lance-shaped to elliptical, measuring 2.5-5 cm x 1-2.5 cm, wedge-shaped at the base, entire at the margin, acute at the apex, hairless and with gland-dotted on both surfaces.
The inflorescence is up to 15 cm long, composed of decussate, with 3-flowered cymes and appears as 6-flowered whorls (verticillasters), which is up to 3 cm apart, terminal, simple or branched. The peduncle and axis are quadrangular. The 2-3 mm long bracts are elliptical-lance-shaped, hairy and persistent. The pedicel is up to 4 mm long and strongly recurved at the top. The sepal is bilobed where in the flower it is 2-2.5 mm long while in the fruit is 3-4.5 mm long. It is villous inside and pubescent with long white hairs outside. The upper lobe is flat and suborbicular while the lower lobe is canaliculated and sharply 4-toothed at the top. The petal is tubular, 2-lipped, measures 4-6 mm long and white. The upper lip is strongly recurved at the top and crenately 4-lobed while the lower lip is entire and smaller than the upper lip. There are 4 didynamous stamens, which are slender and exserted. The pistil is with 4-ovuled and 4-lobed ovary, slender style and with 2-lobed stigma.
The fruit is composed of 4 distinct nutlets that enclosed within the tube of the persistent sepal. The black nutlets are ovoid and measuring up to 1.25 mm x 1 mm. The nutlet-wall produces a thick white cover of slimy threads within several minutes in water. The seed is free within the nutlet.
Ecology / Cultivation
O. americanum is often found growing on roadsides, in fields, in teak forests, and in open waste places close to settlements. It prefers sunny and wind-sheltered spots. It grows well from the plains up to 500(-2000) m altitude, preferably on upland soils, but it is also planted on dikelets of paddy fields.
Line Drawing / Photograph
References
- Plant Resources of South-East Asia No. 8: Vegetables.
