Plectranthus rotundifolius (Poiret) Sprengel
Family
Labiatae
Synonyms
Coleus tuberosus (Blume) Bentham, Coleus parviflorus Bentham, Solenostemon rotundifolius (Poiret) J.K. Morton.
Vernacular Names
| Malaysia | Ubi kembili, ubi keling. |
| English | Madagascar potato, Hausa potato, country potato. |
| Indonesia | Kentang Jawa (Indonesian), kentang ireng (Javanese), huwi kentang (Sundanese). |
| Thailand | Man-khinu, man-nu (Southern). |
| French | Pomme de terre de Madagascar. |
Geographical Distributions
The origin of Plectranthus rotundifolius is thought to lie in Madagascar or tropical Africa, but at present it is only known from cultivation. It is frequently cultivated in Madagascar, tropical and southern Africa, Sri Lanka, India, throughout continental Asia to Peninsular Malaysia, Sumatra, Java, the Moluccas and possibly in the Philippines.
Description
P. rotundifolius is a perennial, aromatic, semi-succulent herb that can grow up to 1 m tall and it is cultivated as an annual. The roots produce ovoid to oblongoid sessile potato-like tubers, measuring up to 4.5 cm x 1.5 cm, blackish, brownish, reddish-grey or whitish and with rough skin.
The stem is decumbent or ascending, quadrangular, with densely pubescent on the angles and roots at the nodes.
The leaves are rather thick, juicy, faintly aromatic when bruised and arranged oppositely. The petiole is 1-3(-5) cm long and puberulous. The blade is ovate to sub-orbicular, measuring 2-6 cm x 1.5-4 cm, wedge-shaped at the base, coarsely crenate at the margins, puberulous at the apex and with gland-dotted below.
The inflorescence is a terminal false spike, measures 5-15 cm long and with verticillasters of 4-6 flowers. The pedicel is 1-2 mm long. The bracts are small. The sepal is bell-shaped, measures 1.5-3 mm long, glandular-hispid and with 5-toothed. The upper tooth is oblong, acute and very short median teeth with rounded apex while the lower teeth is highly connate that forms an almost truncate apex but ends abruptly in 2 widely apart acute tips. The petal is tubular and 2-lipped, measures 7-12 mm long, light to dark violet, pubescent and with gland-dotted. The tube is strongly curved. The upper lip is very short and with 4-lobed while the lower lip is boat-shaped. There are 4 stamens that curved within the lower lip. They are up to 2.5 mm long, shortly unite at the base and envelope the style. The style is with 2-fid and slightly exceeding the stamens.
The fruit is unknown.
Ecology / Cultivation
P. rotundifolius is preferably grown in the tropical high rainfall lowlands, rarely up to 1000 m altitude. Evenly distributed rainfall and low night temperature favour the tuber development. The crop cannot stand waterlogging. Well-drained sandy loams are preferred, but heavy clays are unsuitable. In Southeast Asia, it is often planted on dry rice fields after rice.
Line Drawing / Photograph
References
- Plant Resources of South-East Asia No. 9: Plants yielding non-seed carbohydrates.
