Vernonia hymenolepis (PROTA)

Plant Resources of Tropical Africa Introduction

List of species

General importance
Geographic coverage Africa
Geographic coverage World
Medicinal
Ornamental

Vernonia hymenolepis A.Rich.

Protologue: Tent. fl. Abyss. 1: 378 (1848).

Family: Asteraceae (Compositae)

Chromosome number: 2n = 20

Synonyms

Vernonia calvoana (Hook.f.) Hook.f. (1868), Vernonia leucocalyx O.Hoffm. (1901), Baccharoides calvoana (Hook.f.) M.A.Isawumi (1993).

Vernacular names

Sweet bitterleaf, bitterleaf (En). Vernonie douce, vernonie, ndole (Fr).

Origin and geographic distribution

Vernonia hymenolepis occurs locally wild in mountainous and high plateau regions of West, Central, East and southern Africa. Its cultivation is only known from Nigeria and Cameroon.

Uses

Vernonia hymenolepis is especially appreciated in Cameroon, where it is known as ‘bayangi bitterleaf’ or ‘ndole’. The leaves are consumed fresh and in dry form as a garnish, potherb or salad. The plant is sometimes planted as a hedge around homes and gardens both for vegetable use and for the ornamental value of the large white or purple flowering heads. The plants also help to stabilize the soil, especially on slopes. Vernonia hymenolepis is used medicinally as a cure for pneumonia, and a hot leaf placed on a wound is said to stop bleeding. Juice from crushed leaves is used to treat diarrhoea in babies and jaundice. In Kenya a root decoction is used as a purgative and to treat abdominal pains. Dry branches and stems serve as fuel.

Production and international trade

The production of this vegetable mainly takes place on mixed cropped farms and in home gardens. In western Cameroon there are specialized farms with sweet bitterleaf as the main crop, and this type of production appears to be on the increase. During the dry season, an irrigated sweet bitterleaf crop may fetch a high price at the markets, particularly since at this time it is not as bitter as Vernonia amygdalina Delile. The produce is sold both at local markets and in the big cities. Deep frozen and dried leaves of Vernonia hymenolepis, Vernonia amygdalina and Vernonia colorata (Willd.) W.F.M.Drake are exported from Nigeria and Cameroon to the major markets of African vegetables in Europe.

Properties

The nutritional composition of Vernonia hymenolepis leaves is comparable to that of bitterleaf (Vernonia amygdalina). It is less bitter than other Vernonia species. The sesquiterpene lactone vernolepin was isolated from Vernonia hymenolepis collected in Ethiopia. This compound showed antitumour activity and platelet anti-aggregating properties.

Adulterations and substitutes

Vernonia hymenolepis used in dishes may be replaced by Vernonia amygdalina and other Vernonia species.

Description

Perennial herb, shrub or small tree up to 12 m tall; young branches densely tomentose. Leaves alternate, simple, sessile; blade elliptical to lanceolate, 5.5–34 cm × 1–9.5 cm, cuneate to long-attenuate and sometimes auriculate at base, acuminate at apex, margin minutely to coarsely toothed, pubescent below, pinnately veined. Inflorescence a head, arranged in terminal, compound, umbel-like cymes; involucre ovoid to hemispherical, 1.5–4 cm long, bracts 2–6-seriate, up to 3.5 cm long, with green or white appendages, recurved or not. Flowers bisexual, regular, 5-merous, strongly exserted from the involucre; pappus consisting of many-seriate bristles, up to 1.5 cm long, pale brown; corolla tubular, 1–2 cm long, whitish to purple, glandular, with short, erect lobes; stamens with anthers united into a tube, with appendages at apex; ovary inferior, 1-celled, glabrous to pubescent, style hairy, 2-branched. Fruit a ribbed achene 3–6.5 mm long, glabrous to slightly pubescent, dark brown, crowned by the much longer, caducous pappus bristles. Seedling with epigeal germination; hypocotyl 1–3 cm long, epicotyl 2–6 mm long; cotyledons elliptical, 0.5–1.5 cm long, green.

Other botanical information

Vernonia is the largest genus of the tribe Vernonieae with close to 1000 species; it occurs mainly in South America and Africa. More than 300 species have been described from Africa with about one third occurring in Madagascar.

Vernonia calvoana is considered here as a synonym of Vernonia hymenolepis. However, it is often considered as distinct, differing in often larger, less densely pubescent leaves, usually larger and recurving involucral bracts and more often glabrous fruits. The species show considerable overlap in these characters.

Growth and development

Emergence of the seedling starts about 5 days after sowing. Early growth during the rainy season is so rapid that plants grow as tall as 40–50 cm in just 4 weeks. This rapid growth continues as long as there is ample moisture in the soil. Flower initiation begins with the onset of the dry season or during periods of drought. The degree of soil fertility greatly influences leaf size.

Ecology

Vernonia hymenolepis occurs along rivers and roadsides, in forest margins, old cultivation sites and bushed grassland, but also in montane forest. It is often found in disturbed habitats. Plants thrive at temperatures of less than 30°C at altitudes of (600–)1400–3000 m. The minimum rainfall required is 840 mm/year. Generally, the plants grow well in loose, moist soil rich in humus.

Propagation and planting

Seeds are collected from dry flower heads by rubbing them, followed by winnowing. The 1000-seed weight is 2.4 g. Propagation usually takes place by broadcasting or by sowing in lines on raised beds. Nursery beds are shaded to prevent excessive evaporation. When the seedlings are 2–3 weeks old with 4–6 leaves, they are pruned by nipping the growing point and then transplanted with a ball of soil. At this stage, bitter seedlings are screened by tasting one of their leaves. This selection process not only secures a better quality crop, but also serves to reduce bitterness in the next generations. In sole cropping, seedlings are transplanted at a spacing of 20 cm × 30 cm or even closer; when intercropped in home gardens the spacing is about 75 cm × 75 cm. Some farmers sow directly in lines spaced at 30 cm and thin their crop to a distance of 20–25 cm at the 3–4-week stage. The thinned material can be sold to other farmers as seedlings or consumed. Propagation by cuttings is sometimes practised to multiply selected plants. Cuttings with 4 buds taken from mature plants are used; they are planted slanting. Rooting of the cuttings is not always successful and plant growth is much slower than in seedlings, so that this method is only used in home gardens when a particular plant type is appreciated.

Management

Sweet bitterleaf is very sensitive to drought and should therefore be irrigated daily. Weeding is hardly required in a closely spaced monocrop. Mulching is occasionally practised. Urea is applied as a topdressing to promote regrowth of new leaves after harvest. Ratoon cropping is practised in south-western Cameroon: shoots are harvested about 10 cm above ground level, allowing new shoots to develop. Some farmers only harvest once and re-sow immediately thereafter because young plants grow faster than side shoots. In this case farmers may use a planting distance of 20 cm × 20 cm only.

Diseases and pests

Main diseases of sweet bitterleaf are a potyvirus causing leaf mosaic, green vein banding and distortion of the leaves, and wilting caused by Fusarium sp., which may kill the plants. Pests include snails, crickets and variegated grasshopper (Zonocerus variegatus), which cuts off young leaves and stems. Methyl-paraffin is used for control.

Harvesting

Picking of leaves starts at 4–6 weeks after sowing or 6–8 weeks after transplanting. Harvesting is done either by cutting the young shoots or gathering the leaves only. Although the harvest of leaves only is often preferred, this system may adversely affect the development of the plant. Best results are obtained during the rainy season by cutting the shoots at 5–10 cm above the soil, which will then be replaced by one or two side shoots. These side shoots could be harvested 3–4 weeks later and, depending on soil moisture and fertility, this process could be repeated two or three times. In the dry season, when new shoots develop only slowly if at all, farmers pick leaves only. With adequate irrigation, the ratoon system is possible even during the dry season.

Yield

Highest yields are obtained during the rainy season. In Cameroon the period May–August is the peak harvesting period, when a bundle of 15–20 stems of 40–50 cm and occasionally as long as 90 cm could weigh about 1 kg. Stem weight, quantity and quality are greatly reduced in the dry season. The initial harvest yields about 1 kg/m² which decreases to about 500 g/m² at the third harvest. No data are available for leaf yield.

Handling after harvest

The harvested produce is left in a cool place and when needed water is sprinkled to delay shrinking. Leaves are sliced, washed and squeezed. To reduce bitterness, people may rub the leaves or boil them for 5 minutes in water containing lime. Freezing or drying and packaging may follow. Dried leaves may be reduced to powder but this process changes the taste. The dry leaves must be steeped in water before consumption.

Genetic resources

Vernonia hymenolepis is widespread and occurs often in disturbed habitats, and there is no danger of genetic erosion. Its diversity in the wild is great, but as yet hardly studied or exploited. Wild, often purple-flowered plants are very bitter.

Breeding

Cross-pollination takes place through both insects and the wind. Isolation at the propagation stage is therefore important since crosses between wild and cultivated plants often result in bitter-tasting plants.

Prospects

Vernonia hymenolepis is a much appreciated but rather scarce vegetable. Vegetative propagation would be the best way to maintain uniformity, but poor rooting and slow regrowth remain a problem. Once new and uniform cultivars are developed and high quality seed becomes available, this species may well take over the whole market for bitterleaf including the common bitterleaf (Vernonia amygdalina). Processing the leaves before marketing them could become a new source of income as consumers would not need to spend so much time on the preparation of dishes, which may be important for people in cities.

Major references

• 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.

• Besong, B.F. & Abia, C., 1998. The production of bayangi bitterleaf in S.W. Cameroon. Unpublished paper produced for the Natural Resources Institute, Chatham, United Kingdom. 11 pp.

• Biholong, M., 1986. Contribution à l’étude de la flore du Cameroun. Les Asteraceae. Thèse de Doctorat d’Université de Bordeaux III, Bordeaux, France. 354 pp.

• Dupriez, H. & De Leener, P., 1989. African gardens and orchards, growing vegetables and fruits. MacMillan Press, London, United Kingdom. 333 pp.

• Fube, H.N. & Djonga, B., 1987. Tropical vegetables in human nutrition: a case of ndolé (bitterleaf) Vernonia calvoana Hook. Acta Horticulturae 198: 199–206.

• Kalanda, K. & Lisowski, S., 1995. Le genre Vernonia (Asteraceae) dans la flore d’Afrique Centrale (Zaïre, Rwanda, Burundi). Fragmenta Floristica et Geobotanica 40(2): 547–717.

• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.

• Schippers, R.R., 2000. African indigenous vegetables. An overview of the cultivated species. Natural Resources Institute/ACP-EU Technical Centre for Agricultural and Rural Cooperation, Chatham, United Kingdom. 214 pp.

• Stevels, J.M.C., 1990. Légumes traditionnels du Cameroun: une étude agrobotanique. Wageningen Agricultural University Papers 90–1. Wageningen Agricultural University, Wageningen, Netherlands. 262 pp.

Other references

• Burkill, H.M., 1985. The useful plants of West Tropical Africa. 2nd Edition. Volume 1, Families A–D. Royal Botanic Gardens, Kew, Richmond, United Kingdom. 960 pp.

• Fidelia, U.F., 2000. Morphological variation and the effects of processing on edible Vernonia spp. (bitterleaf). Students dissertation. Dschang University, Menoua, Cameroon.

• Isawumi, M.A., 1993. New combinations in Baccharoides Moench (Vernoniae; Compositae) in West Africa. Feddes Repertorium 104(5–6): 309–326.

• Jeffrey, C., 1988. The Vernonieae in East Tropical Africa. Notes on Compositae 5. Kew Bulletin 43(2): 195–277.

• Kupchan, S.M., Hemingway, R.J., Werner, D., Karim, A., McPhail, A.T. & Sim, G.A., 1968. Tumor inhibitors. 31. Vernolepin, a novel elemanolide dilactone tumor inhibitor from Vernonia hymenolepis. Journal of the American Society of Chemistry 90: 3596–3597.

• Mbinglo, S.B., 1998. Survey on the production of bitterleaf Vernonia spp. in Bamenda, N.W. Cameroon. Student project report for Natural Resource Institute, Chatham, United Kingdom/Dschang University, Cameroon.

• Numfor, F.A., 1997. Post-harvest processing and preservation of indigenous vegetables in Cameroon: problems and constraints. In: Schippers, R.R. & Budd, L. (Editors). Proceedings of a workshop on African indigenous vegetables, Limbe, Cameroon, 13–18 January 1997. Natural Resources Institute/IPGRI, Chatham, United Kingdom. p. 64.

• Tabuna, H., 2000. Evaluation des échanges des produits forestiers non ligneux entre l’Afrique subsaharienne et l’Europe. [Internet] FAO, Rome, Italy. http://www.fao.org/DOCREP/003/X6612F/x6612f00.htm. 2 March 2004.

Sources of illustration

• Stevels, J.M.C., 1990. Légumes traditionnels du Cameroun: une étude agrobotanique. Wageningen Agricultural University Papers 90–1. Wageningen Agricultural University, Wageningen, Netherlands. 262 pp.

Author(s)

• F. Ucheck Fomum

c/o Cheten Louis Bernard, P.O. Box 219, Bafoussam, Cameroon

Correct citation of this article

Ucheck Fomum, F., 2004. Vernonia hymenolepis A.Rich. [Internet] Record from PROTA4U. Grubben, G.J.H. & Denton, O.A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. <http://www.prota4u.org/search.asp>.

Accessed 18 December 2024.

• See the Prota4U database.