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Commelina benghalensis L.

Protologue
Sp. pl. 1: 41 (1753).
Family
Commelinaceae
Chromosome number
2n = 22
Synonyms
Commelina pyrrhoblepharis Hassk. (1867).
Vernacular names
Blue commelina, venus’ bath, Benghal dayflower, tropical spiderwort (En). Commeline, comméline (Fr). Trapoeraba (Po). Kongwa, kafula, mpovupovu (Sw).
Origin and geographic distribution
Commelina benghalensis is originally an Old World species, and is naturalized in the Americas and Hawaii. It occurs throughout tropical Africa from Cape Verde and Senegal to Ethiopia, and south to South Africa; it also occurs in Madagascar and the Mascarene Islands.
Uses
In parts of West Africa, e.g. Côte d’Ivoire and Ghana, the leaves of Commelina benghalensis are cooked and eaten as a vegetable. The leaves are mucilagenous. In Kenya young leaves are eaten as a relish; older leaves are regarded as too acidic and bitter to use. In Kenya, Uganda and Tanzania the leaves and stems are chopped and cooked alone or with other vegetables such as Bidens pilosa L. or Cleome hirta Oliv. It is also reported as a vegetable in Ethiopia. In Indonesia the leaves and young tops are occasionally steamed and eaten as a vegetable, and in the Philippines they are eaten cooked. In India the leaves are eaten as famine food.
In Sudan and eastern Africa the plants are grazed by domestic stock, at the same time providing part of the cattle’s need for water. In northern Ghana it is a favourite feed for pigs and poultry; in Tanzania it is given to animals, especially pigs and rabbits. The flowers provide bee forage. In southern Africa however, its use as pig feed is restricted to times of scarcity as it is thought to cause a sort of ‘measles’ in the animals. There may be edaphic or genetic differences causing such differences in properties, but these may also originate from misidentifications, because most Commelina species resemble each other very closely.
In southern Nigeria the plant is used as a poultice for sore feet. In East Africa the sap of Commelina benghalensis leaves and stems is used to treat ophthalmia, sore throat and burns, and the liquid contained in the flowering spathe is used to treat eye complaints in Zanzibar. In Uganda and Tanzania the sap is used topically against thrush in infants, and in Tanzania a solution of pounded leaves soaked in warm water to treat diarrhoea. In southern Africa Commelina benghalensis is used to counter infertility in women, and a decoction of the root is used for the relief of stomach disorders. In India it is said to be beneficial for leprosy, and in the Philippines it is used as an emollient suppository for strangury. In Rajasthan (India) sheep with jaundice are treated with a mixture of the plant with whey and common salt.
The rhizomes are starchy and mucilaginous. In India and Sudan they are commonly cooked and eaten, and are said to be a wholesome food. In India and China a dye is obtained from the sap of the flowers.
Properties
Dry leaves of a sample of Commelina benghalensis from Bouaké, Côte d’Ivoire, contained per 100 g: protein 13.6 g, fat 2.1 g, carbohydrate 58 g, fibre 41 g (Busson, 1965). All aboveground parts are astringent and contain hydrocyanic acid. Commelina benghalensis has given negative results in tests for antibacterial effects.
Botany
Perennial herb with tuberous fusiform fleshy roots; stems erect or creeping-ascending, often with subterranean cleistogamous flowers. Leaves arranged spirally, simple; sheath 0.5–3 cm long with purple veins, ciliate with purple 3–7 mm long bristles along free edges, rarely over the surface, otherwise glabrous or with hooked hairs; blade generally broadly lanceolate, 9–12 cm × 3–5 cm, pseudo-petiole 3–15 mm long with a few purple or white bristles 3–7 mm long, apex acute or acuminate, pubescent or glabrous, veins parallel. Inflorescence a leaf opposed, falsely terminal cyme; peduncle up to 6 mm long; spathe funnel-shaped 1–2 cm long, margins completely fused, pubescent with short hooked hairs and sparsely pilose with straight hairs. Flowers bisexual, zygomorphic, protruding from the spathe when flowering, with pedicel 4–7 mm long, reflexed and enclosed in the spathe when fruiting; petals blue, lower petal smaller than the 2 upper petals, these with claw 4–5 mm long, lamina 8 mm × 10 mm; upper three stamens sterile, with cross-shaped, yellow anthers, medial stamen with filament 5–7 mm long and fertile, blue anther c. 2 mm long, the two lateral (lower) stamens with smaller fertile, blue anthers c. 1.4 mm long. Fruit a capsule 4.5–5.5 mm long, 3-celled, 3–5-seeded, the 2 ventral locules each 1(–2)-seeded, dehiscent, the dorsal locule 1-seeded, delayed or immediately dehiscent. Seeds variable in size, cylindrical-rectangular in outline, 2–5.5 mm × 1.5–2.2 mm, brown; testa reticulate with tuberculate ridges, provided with farinose granules; hilum normally linear, 1–3 mm long, not reaching the ends.
Blue-flowered Commelina species such as Commelina benghalensis and Commelina diffusa Burm.f. are easily confused. Both species are common throughout Africa. The properties attributed to one species may therefore also be valid for the other. In East Africa Commelina imberbis Ehrenb. ex Hassk. and Commelina latifolia Hochst. ex A.Rich. are also used as a vegetable. Commelina zambesica C.B.Clarke is used as a vegetable on Pemba Island (Tanzania).
The flowers of Commelina benghalensis open from 8 a.m. to noon.
Ecology
Commelina benghalensis is common in disturbed areas, at forest edges, along roadsides, in secondary regrowth and fields, on waste ground and in home gardens. It can withstand prolonged drought. It is a very serious weed on farms; in Benin it is reported to be a noxious weed in cotton fields.
Management
In Tanzania Commelina benghalensis is not cultivated or protected by local people. The leaves are collected during the early flush of the rainy season for immediate use. They are not stored. The plants are said to produce 14,000 seeds per plant above ground, and fewer in the soil (cleistogamous flowers), but the latter germinate to a high degree, and weed control is therefore cumbersome. It is a weed in both the drier north of Benin (where it may have an annual life cycle) and in the more humid south. It is a serious weed in other regions of the world as well as is illustrated by its appearance on the federal noxious weed list of the United States.
Genetic resources and breeding
Because of its abundance and weedy nature, there is no danger of genetic erosion for Commelina benghalensis.
Prospects
Despite its several uses, the plant is reported not to be marketed in Tanzania. The bleak prospects of commercialization as a vegetable do not seem to justify domestication research.
Major references
• Ahanchede, A. & Gasquez, J., 1992. Variabilité enzymatique de Commelina benghalensis (L.) au Bénin. In: 9me Colloque International sur la Biologie des Mauvaises Herbes. Dijon, France. pp. 427–436.
• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, United Kingdom. 960 pp.
• Busson, F., 1965. Plantes alimentaires de l’ouest Africain: étude botanique, biologique et chimique. Leconte, Marseille, France. 568 pp.
• Isa Ipor, 2001. Commelina L. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 181–185.
• Ruffo, C.K., Birnie, A. & Tengnäs, B., 2002. Edible wild plants of Tanzania. Technical Handbook No 27. Regional Land Management Unit/ SIDA, Nairobi, Kenya. 766 pp.
• Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.
Other references
• Alam, N. & Sharma, A.K., 1984. Trends of chromosome evolution in family Commelinaceae. Nucleus 27: 231–241.
• Cufodontis, G., 1962–1969. Beitrag zur Flora von Godjam. Senckenbergiana Biologica 43: 301–330; 46: 115; 47: 273; 50: 281.
• Fynn, D.F., 1999. Cytotoxicity assay of Commelina diffusa and Commelina benghalensis using the brine shrimp lethality test. BSc thesis, Department of Pharmacognosy, Faculty of Pharmacy, Kwame Nkrumah University of Science and Technology, Kumasi, Ghana. 50 pp.
• Irvine, F.R., 1930. Plants of the Gold Coast. Oxford University Press, London, United Kingdom. 522 pp.
• Kelbessa, E. & Faden, B., 1997. Commelinaceae. In: Edwards, S., Mesfin Tadesse, Demissew Sebsebe & Hedberg, I. (Editors). Flora of Ethiopia and Eritrea. Volume 6. Hydrocharitaceae to Arecaceae. The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. pp. 339–374.
• Mathias, E., Rangnekar, D.V. & McCorkle, C.M., 1999. Ethnoveterinary medicine: alternatives for livestock development. [Internet] www.vetwork.org.uk/pune12.htm. Accessed 27 March 2003.
• van den Bergh, M.H., 1993. Minor vegetables. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 280–310.
• Vanden Berghen, C., 1988. Flore illustrée du Sénégal. Monocotylédones et Ptéridophytes. Volume 9. Monocotylédones: Agavacées à Orchidacées. Gouvernement du Sénégal, Ministère du Développement Rural et de l’Hydraulique, Direction des Eaux et Forêts, Dakar, Senegal. 522 pp.
• van Wyk, B.E. & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza Publications, Pretoria, South Africa. 351 pp.
Sources of illustration
• Isa Ipor, 2001. Commelina L. In: van Valkenburg, J.L.C.H. & Bunyapraphatsara, N. (Editors). Plant Resources of South-East Asia No 12(2): Medicinal and poisonous plants 2. Backhuys Publishers, Leiden, Netherlands. pp. 181–185.
Author(s)
W.J. van der Burg
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
G.J.H. Grubben
Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate Editors
C.-M. Messiaen
Bat. B 3, Résidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
Illustrator
PROSEA
PROSEA Network Office, Herbarium Bogoriense, P.O. Box 234, Bogor 16122, Indonesia

Correct citation of this article:
van der Burg, W.J., 2004. Commelina benghalensis L. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, flowering stem; 2, inflorescence; 3, opened spathe with fruits; 4, seed.
Source: PROSEA