Prota 2: Vegetables/Légumes
2n = 10
Sonchus cornutus Hochst. ex Oliv. & Hiern (1877), Sonchus exauriculatus (Oliv. & Hiern) O. Hoffm. (1895).
Bitter lettuce (En). Laitue amère (Fr). Mtsunga (Sw).
Origin and geographic distribution
Launaea cornuta is distributed from Nigeria east to Djibouti and Somalia and south to Zimbabwe and Mozambique. It is mainly used as a vegetable in East Africa.
The leaves of bitter lettuce are cooked and eaten with amaranth, pumpkin or cowpea leaves. When there are no other vegetables present to mix bitter lettuce with, people replace the cooking water to reduce the bitter taste. Bitter lettuce is an important vegetable for the Giriama, Kamba, Taita and other coastal tribes in Kenya and Somalia, and also for the Sambaa people of Tanzania’s Usambara Mountains. In these areas, especially amongst the Giriama people, it has several ceremonial uses. Coastal people believe that it can prevent and cure malaria, whereas people with stomach problems or ulcers should not eat it. The rhizomes are used in Malawi and Tanzania as a cure against venereal diseases and hookworm. In Kenya and Tanzania the roots are chewed in case of swollen testicles, they are boiled to make a drink against cough and typhus, and an infusion of the root is used as an eye wash and against earache. In Kenya a decoction of the whole plant is used externally to treat measles. In Sudan it is used to give a bitter taste to beer. The leaves are fed to cattle in Tanzania to increase the milk yield.
Production and international trade
The leaves are mostly collected from the wild, but some cultivation takes place in Ethiopia, Somalia, Kenya and Tanzania, mainly in home gardens. Of late, production in a peri -urban environment for city markets is emerging. This vegetable is frequently found on local markets in the coastal zones of Kenya and Tanzania, and also in the Usambara Mountains, but no cross-border trade is known to take place.
The nutritional composition of young Launaea cornuta leaves is per 100 g edible portion: water 86.8 g, protein 3.9 g, fat 0.9 g, carbohydrate 4.5 g, Ca 214 mg, P 13.2 mg, Fe 7.2 mg, ascorbic acid 18.7 mg (Ndossi, G.D. & Sreeramulu, N., 1991). The leaves contain a milky white fluid and are generally bitter in taste, although there are some selections that are referred to as sweet.
Adulterations and substitutes
The leaves of bitter lettuce can be replaced by Sonchus oleraceus L. or Launaea taraxacifolia (Willd.) Amin ex C.Jeffrey leaves.
Perennial herb up to 100(–150) cm tall, with creeping root system; stem erect, hollow, slightly glaucous. Leaves at base of plant in a rosette, alternate on stem, without stipules, sessile, obovate or broadly spatulate to narrowly elliptical or lanceolate in outline, 2–25 cm × 0.5–8 cm, simple to deeply pinnatifid, lower leaves tapering at base, higher ones auriculate, toothed. Inflorescence a 15–27-flowered head arranged in a divaricately branched, bracteate synflorescence; peduncle 0.5–2.5 cm long, often with stalked glands; involucre with imbricate outer bracts and a single row of longer, linear-lanceolate inner bracts 8–13 mm long. Flowers all ligulate; corolla with tube c. 0.5 cm long and ligule c. 1 cm long, pale yellow; stamens 5, anthers united into a tube, blackish yellow; ovary inferior, 1-celled, style 2-branched. Fruit a cylindrical to fusiform achene 2.5–4.5 mm long, ribbed, crowned by white pappus hairs 5–7 mm long.
Other botanical information
Launaea comprises about 55 species and occurs in Africa and south -western Asia, but a single species (Launaea intybacea (Jacq.) Beauverd) has been introduced and naturalized in the Caribbean region and Central America. Northern and eastern Africa are particularly rich in species. Launaea is placed in tribe Lactuceae subtribe Sonchinae, together with e.g. Reichardia and Sonchus.
Growth and development
Seed germinates within a few days. After emergence, the young plant develops a rosette of leaves. A leafy flowering stalk is soon formed. In Kenya and Tanzania flowering is year-round. Plants are self-fertile. After fruiting new growth develops from the base of the stem and from the root. Even during the dry season the plants form new rosette leaves and they keep producing new shoots from the roots for several years.
Launaea cornuta grows in disturbed localities such as roadsides or as a troublesome weed in perennial plantations of trees or shrubs. It can also be found in grassland. It is most common in the hot lowland coastal zones of East Africa and near the great lakes and less common in highland areas up to 2300 m altitude. It prefers sandy soils in relatively dry localities, but also grows on loam and even black cotton soils.
Care should be taken to prevent bitter lettuce spreading as a weed.
Propagation and planting
Bitter lettuce can be propagated vegetatively. People may select plants from the wild that are sweet or only slightly bitter, and plant these in their garden. Some gardeners split the roots from carefully selected plants to produce a number of new plantlets and thus create a uniform crop of the desirable type.
People select young, large rosette leaves because older leaves and small stem leaves are usually too bitter.
Launaea cornuta is a common weed not threatened by genetic erosion. Selections of less bitter types, made by farmers, are readily available.
Launaea cornuta is quite a popular wild vegetable in East Africa. Domestication is taking place locally. Bitter lettuce merits attention in agronomic research and breeding.
• Agnew, A.D.Q. & Agnew, S., 1994. Upland Kenya wild flowers: a flora of the ferns and herbaceous flowering plants of upland Kenya. 2nd Edition. East Africa Natural History Society, Nairobi, Kenya. 374 pp.
• 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.
• Kilian, N., 1997. Revision of Launaea Cass. (Compositae, Lactuceae, Sonchinae). Englera 17: 1–478.
• Leung, W.-T.W., Busson, F. & Jardin, C., 1968. Food composition table for use in Africa. FAO, Rome, Italy. 306 pp.
• Maundu, P.M., Ngugi, G.W. & Kabuye, C.H.S., 1999. Traditional food plants of Kenya. Kenya Resource Centre for Indigenous Knowledge (KENRIK), Nairobi, Kenya. 270 pp.
• Schippers, R.R., 2002. African indigenous vegetables, an overview of the cultivated species 2002. Revised edition on CD-ROM. National Resources International Limited, Aylesford, United Kingdom.
• Beentje, H.J., 2000. Compositae (part 1). In: Beentje, H.J. (Editor). Flora of Tropical East Africa. A.A. Balkema, Rotterdam, Netherlands. pp. 1–313.
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• Ndossi, G.D. & Sreeramulu, N., 1991. Chemical studies on the nutritional value of Launaea cornuta - a wild leafy vegetable. Journal of Food Science and Technology 28(3): 183–184.
• Pope, G.V., 1992. Compositae. In: Pope, G.V. (Editor). Flora Zambesiaca. Volume 6, part 1. Flora Zambesiaca Managing Committee, London, United Kingdom. 264 pp.
Correct citation of this article:
Schippers, R.R., 2004. Launaea cornuta (Hochst. ex Oliv. & Hiern) C.Jeffrey In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
close up of flowers