Some species of Plectranthus are difficult to identify because of a lack of clear-cut morphological criteria to discriminate not only among species within the genus but also among the closely related genera. This has resulted in numerous taxonomic problems in the naming of species with the result that species have often been placed in several closely related genera like Coleus, Solenostemon and Englerastrum. In addition, some species formally placed in Plectranthus, are now recognized as the more distantly related genus Isodon.
Because of these taxonomic issues, different names have often been used for the same species of Plectranthus and thus it has been difficult to collate information about the ethnobotanical uses of this genus. Furthermore, the most commonly used medicinal species of Plectranthus have a high degree of synonymy[].
This report is very much indebted to the work of C.W. Lukhoba et al. - Journal of Ethnopharmacology 103 (2006) 1–24[] in untangling much of this mess of names, and utilizes the on-line Kew database ‘World Checklist of Selected Plant Families (http://wcsp.science.kew.org/home.do) for determining currently accepted names and synonyms (as of 2018).

Common Name: Hausa Potato

General Information

Plectranthus rotundifolius is an aromatic, perennial, semi-succulent plant producing erect or decumbent stems that can be 30 - 100cm long from a tuberous rootstock. The plant forms new tubers in clusters around the bases of the stems[, ].
The plant used to be widely cultivated as a root crop in the savanah belt of Africa, though it has largely fallen out of favour there. It is still sometimes cultivated in Africa, but is much more commonly grown in southeast Asia[, ].
A widespread plant, it is classified as 'Least Concern' in the IUCN Red List of Threatened Species(2013)[].

Known Hazards

None known

Botanical References

Range

E. Asia - India, Sri Lanka, Thailand, Vietnam, Malaysia, Indonesia, Philippines; widely cultivated in tropical Africa

Habitat

Plants are sometimes found in a more or less wild setting, growing in grassland in the savannah at elevations up to 2,200 metres[].

Properties

Conservation Status	Least Concern
Edibility Rating
Medicinal Rating
Habit	Perennial
Height	0.50 m
Pollinators	Insects
Cultivation Status	Cultivated

Cultivation Details

A plant of the moist tropics. It grows best in areas where annual daytime temperatures are within the range 17 - 27°c, but can tolerate 8 - 36°c[]. Lower night temperatures promote tuber development[]. It prefers a mean annual rainfall in the range 1,800 - 2,600mm, but tolerates 1,200 - 4,000mm[]. Plants are adapted to relatively high rainfall - the best yields are obtained in areas with rainfall well distributed through the growing season[]. When there is too much rain, the tubers tend to branch, which is disliked by consumers because they are then difficult to peel[].
Requires a sunny position[, ]. Prefers a well-drained sandy loam, but can tolerate a range of soils[, ]. Tolerant of poorer, dry soils, though yields are lower in such conditions[]. Yields are low in heavy soils[]. Prefers a pH in the range 6.5 - 7.5, tolerating 5.5 - 8[]. Dislikes waterlogged soils[].
Plants take 5 - 7 months from planting to harvesting the tubers[]. The tubers are formed on stems that are in contact with the soil - yields from 7 - 15 tonnes per hectare have been recorded[].
The tubers need to be harvested quickly or they are liable to decay rapidly[].
Hausa potato is difficult to store. Traditionally the tubers are stored in the ground under a tree where it is cooler than in the open. When stored in this way under hot conditions the special taste of Hausa potato usually lasts for two months only, after which the tubers become bland and are no longer considered a delicacy[]. Hausa potato is also packed in bags or baskets stuffed with straw, but if these are kept under warm conditions the tubers will soon shrivel and are no longer edible. To keep the tubers longer, people put them in pots sealed with cow dung. The small tubers needed for the next planting season are stored in this way. In cooler conditions, such as in highland regions or in South Africa, storage is easier[].
There are some named varieties[].

Edible Uses

Tubers - raw or cooked[]. Often eaten as a relish in combination with a starchy staple food, but occasionally they constitute the staple food[]. They are cooked with spices in various combinations with other foods such as beans and cooked vegetables[]. They are eaten cooked or steamed as a vegetable, sometimes even raw; they are also mixed with savor[]. Adult tubers are also used as a substitute for potatoes, for the preparation of minced meatballs[]. They are best consumed in small quantities, as they are somewhat indigestible[]. Used in the same ways as potatoes[, ]. The white, starchy, slightly aromatic tubers become dark with age[]. The tubers are usually 2 - 4cm long, occasionally to 8cm, occurring in clusters of 3 - 7[, ].

Leaves - cooked. Occasionally used as a vegetable[, ].

Medicinal

The leaves are sometimes used in traditional medicine for purposes such as the treatment of dysentery[].
The plant is also used to treat blood in the urine as well as eye disorders[].

Agroforestry Uses:

Hausa potato is grown either as a sole crop or intercropped with bambara groundnut, yam, okra, millet, maize or sorghum[].

Other Uses

None known

Propagation

Seed - not normally used for propagation[].
Cuttings about 10 - 20cm long[]. They can be difficult to root[].
Division of sprouting tubers[]. They are planted about 5 - 8cm deep[].

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