Prota 2: Vegetables/Légumes
Sp. pl. 1: 529 (1753).
Tiliaceae (APG: Malvaceae)
2n = 14
Jew’s mallow, jute mallow, krinkrin, tossa jute, bush okra, West African sorrel (En). Corète potagère, jute potager, mauve des Juifs, craincrain, krinkrin (Fr). Coreté, caruru da Bahia (Po). Mlenda (Sw).
Origin and geographic distribution
The geographical origin of Corchorus olitorius is often disputed, because it has been cultivated since centuries both in Asia and in Africa, and it occurs in the wild in both continents. Some authors consider India or the Indo-Burmese area as the origin of Corchorus olitorius and several other Corchorus species. However, the presence in Africa of more wild Corchorus species and the larger genetic diversity within Corchorus olitorius point to Africa as the first centre of origin of the genus, with a secondary centre of diversity in the Indo-Burmese region. At present Corchorus olitorius is widely spread all over the tropics, and it probably occurs in all countries of tropical Africa.
In tropical Africa it is reported as a wild or cultivated vegetable in many countries. It is a leading leaf vegetable in Côte d’Ivoire, Benin, Nigeria, Cameroon, Sudan, Kenya, Uganda and Zimbabwe. Jew’s mallow is also cultivated as a leaf vegetable in the Caribbean, Brazil, India, Bangladesh, China, Japan, Egypt and the Middle East. It is cultivated for jute production in Asia (India, Bangladesh, China) together with Corchorus capsularis L., but in Africa it is of no importance as a fibre crop, although the fibre may be used domestically.
Jew’s mallow is used as a leafy mucilaginous vegetable. The cooked leaves form a slimy sticky sauce, comparable to okra. In Nigeria this sauce is found suitable for easy consumption of starchy balls made from cassava, yam or millet. A powder prepared from dried leaves is used to prepare this sauce during the dry season. The immature fruits, called bush okra, are also dried and ground to a powder for the preparation of this slimy sauce. In East Africa several recipes exist, e.g. Jew’s mallow may be cooked with cowpeas, pumpkin, cocoyam leaves, sweet potato, milk and butter, meat, and flavoured with peppers and lemon.
Jute has been the most widely used packaging fibre for more than 100 years because of its strength and durability, low production costs, ease of manufacturing and availability in large and uniform quantities. However, jute production is insignificant in Africa. The types of Corchorus olitorius that are used as a leaf vegetable are quite distinct from the types used for jute production.
Root scrapings of Jew’s mallow are used in Kenya to treat toothache, a root decoction as a tonic, leafy twigs in Congo against heart troubles, an infusion from the leaves is taken in Tanzania against constipation, and seeds in Nigeria as a purgative and febrifuge.
Production and international trade
Jew’s mallow is one of the leading leafy vegetables in many countries and much cultivated and traded. No statistical data on production or marketing are available. International trade with neighbouring countries occurs, but is not registered. In Europe, Jew’s mallow is sold in powder form as a Libanese product, under its Arab name ‘meloukhia’.
The world jute production (combined data from Corchorus olitorius and Corchorus capsularis L.) has been stable over the past 40 years. In the period 1997–2001 it averaged 2.76 million t raw fibre per year. India and Bangladesh together produced more than 90% of the total.
The composition of Corchorus olitorius leaves per 100 g fresh edible portion is: water 80.4 g (74.2–91.1), energy 243 kJ (58 kcal), protein 4.5 g, fat 0.3 g, carbohydrate 12.4 g, fibre 2.0 g, Ca 360 mg, P 122 mg, Fe 7.2 mg, β-carotene 6410 μg, thiamin 0.15 mg, riboflavin 0.53 mg, niacin 1.2 mg, ascorbic acid 80 mg (Leung, W.-T.W., Busson, F. & Jardin, C., 1968). This composition is in line with other dark green leaf vegetables, but the dry matter content of fresh Jew’s mallow leaves is higher than average. The composition and especially the micronutrient content are strongly influenced by external factors such as soil fertility and fertilization. Nitrogen fertilizer greatly improves the micronutrient content, e.g. Fe, P, Ca, carotene and vitamin C.
The mucilaginous polysaccharide in the leaves is rich in uronic acid (65%) and consists of rhamnose, galactose, glucose, galacturonic acid and glucuronic acid in a molar ratio of 1.0:0.2:0.2:0.9:1.7 in addition to 3.7% acetyl groups.
Jute fibres are obtained from the bast. The use is limited to coarse fabrics, because the length:diameter ratio of jute filaments is only 100–120, much below the minimum of 1000 required for fine spinning quality. Fibre cells are 2–2.5 mm long and 15–20 μm in diameter. Fibre cells are cemented together into filaments of up to 250 mm long. The tensile strength of jute is 395–775 MPa, the elongation at break is only 1–2%. Jute has a low ignition temperature of 193°C, posing a considerable fire hazard in warehouses.
Corchorus olitorius leaves contain antioxidative phenolic compounds, of which 5-caffeoylquinic acid is the most important. Some ionone glucosides have also been isolated from the leaves; they showed inhibitory activity on histamine release from rat peritoneal exudate cells induced by antigen-antibody reaction. The seeds are poisonous to mammals and insects. They contain cardiac glycosides.
Adulterations and substitutes
As ingredient of slimy sauces Corchorus olitorius can be replaced by other Corchorus species (also called Jew’s mallow): the wild and cultivated Corchorus tridens L. and the wild species Corchorus asplenifolius Burch., Corchorus fascicularis Lam., Corchorus trilocularis L. and Corchorus aestuans L.
Erect annual herb up to 2(–4) m tall, usually strongly branched; stems reddish, fibrous and tough. Leaves alternate, simple; stipules narrowly triangular with long point; petiole (0.5–)1–7 cm long; blade narrowly ovate, ovate or elliptical, 4–15(–20) cm × 2–5(–11) cm, cuneate or obtuse and with setaceous appendages up to 2.5 cm long at base, acuminate to acute at apex, margin serrate or crenate, almost glabrous, usually shiny dark green, 3–7-veined from the base. Inflorescence a 1–4-flowered axillary fascicle, bracteate. Flowers bisexual, regular, usually 5-merous, shortly stalked; sepals free, narrowly obovate, 5–7 mm long; petals free, obovate, 5–7 mm long, yellow, caducous; stamens numerous; ovary superior, usually 5-celled, style short. Fruit a cylindrical capsule up to 7(–10) cm long, ribbed, with a short beak, usually dehiscing by 5 valves, many-seeded. Seeds angular, 1–3 mm long, dark grey. Seedling with epigeal germination; hypocotyl 1–2 cm long; cotyledons foliaceous, broadly elliptical to circular, 3–8 mm long.
Other botanical information
The genus Corchorus comprises an uncertain number of species, with estimates ranging from 40–100. Two important cultivar-groups of Corchorus olitorius exist. The vegetable types are combined in Olitorius Group, characterized by a plant height lower than 2 m, often not more than 1 m, and a more or less heavily branched plant habit. The fibre types are classified in Textilis Group, with plant heights of 4(–5) m and plants only slightly branched at the top. Within Olitorius Group, there are numerous local cultivars, e.g. early and late flowering, and with differences in plant habit and leaf shape. In Nigeria, the popular ‘Amugbadu’ is reputed to be suitable for transplanting and harvest by repeated cuttings; it has finely serrate, elliptical-ovate leaves, whereas ‘Oniyaya’ has smaller and coarsely serrate leaves, is strongly branched and more suitable for direct sowing and once-over harvest. ‘Géant de Bertoua’ from Cameroon has very large, broadly ovate leaf blades. Cultivars with deeply and irregularly serrate leaves (’Incisifolius’) can be found in Benin and Cameroon.
Growth and development
Growth of Corchorus olitorius seedlings is fast. In short day conditions flowering starts about a month after emergence and continues for 1–2 months, depending on type and conditions. The flowers are usually self-pollinated, but cross-pollination up to 10% occurs. After about 3–4 months, the fruits are ripe, the leaves drop and the plant dies.
Wild plants of Corchorus olitorius grow in grassland and fallow or abandoned fields, often close to marshes, rivers and lakes, at up to 1250(–1750) m altitude. Jew’s mallow thrives best under hot and humid conditions. In the savanna and Sahel zone, it performs best during the hot rainy season. It is cultivated where annual rainfall averages 600–2000 mm. The optimal temperature is 25–32°C. Growth stops below 15°C. Jew’s mallow is a short-day species. In Nigeria a daylength of 12.5 hours caused a much stronger vegetative growth expressed in weight of roots, stems and leaves than a day length of 11.5 hours, but the fruit and seed production was higher at a photoperiod of 11.5 hours. Jew’s mallow prefers sandy loam soils rich in organic matter and grows poorly on heavy clay.
Jew’s mallow is usually grown as a rainfed crop without much care. In peri-urban production the growers practise manual irrigation during the dry season, at least 6 mm daily. Organic fertilizer may be applied at up to 20 t/ha. A basal application with NPK (e.g. 15–15–15 at 400 kg/ha) and a side dressing with nitrogen are recommended for an optimal yield. Nitrate fertilizer gives better results than ammonium-based ones.
Propagation and planting
In general farmers have no access to improved seed, but harvest their own. They keep a few plants for that purpose in their garden or field until fruit maturity. For a good seed yield of 25 g per plant, a spacing of 50 cm between and within the row is recommended. Commercial seed production may be 600 kg/ha. The seed is ripe when all the leaves have dropped. For own on-farm seed production, the stems with fruits are harvested, and after drying in the sun they are kept until the next season. In villages in the north of Côte d’Ivoire, the women conserve the fruits in the kitchen above the fireplace. Fruits on abandoned plants in the field also still contain viable seed until the next rainy season. These fruits open at the onset of the rains and the seeds spread. Well-dried seed keeps a high germination capacity for several years. One g contains about 470 seeds. Fresh and sometimes old seed shows dormancy caused by impermeability of the seed coat. This is a major problem for Jew’s mallow cultivation. To suppress the dormancy, it is recommended that the seed tied in a piece of cotton cloth be immersed for 5 seconds in almost-boiling water before sowing. Another method is scarification with sandpaper.
In traditional field cultivation, the farmers broadcast seed without any consideration concerning the optimal density. They often grow Jew’s mallow in association with other vegetables or food crops such as okra, tomato, watermelon, groundnut or yam.
Peri-urban vegetable farmers produce Jew’s mallow on beds in monoculture. Direct sowing is mainly applied for once-over harvest by uprooting or low cutting at soil level. Sowing is done in lines 30–50 cm apart and with spacing 10–15 cm in the rows. For the more common harvesting by repeated cuttings, 10–20 g seed per 10 m2 is sown in a nursery in well-loosened soil. When the seedlings are 5–10 cm tall, they are transplanted at a spacing of 10–20 cm in the row and 30–50 cm between the rows. In trials in Ghana the highest yield, 50 kg of marketable shoots or 29 kg of edible leaves per 10 m2, was obtained with a spacing of 10 cm × 45 cm.
Diseases and pests
Jew’s mallow is rather resistant to diseases and pests. Sclerotium rolfsii causing foot rot and wilting is sometimes a problem. Curvularia species cause black leaf spots, and Cercospora circular leaf spots. These fungal diseases are kept under control by cultivation on well-drained beds and wide spacing. A virus disease transmitted by leaf hoppers and causing leaf deformation and retarded growth was reported from Nigeria.
The most damaging pests are grasshoppers (Zonocerus variegatus), caterpillars (Acrea spp.), army worm (Spodoptera littoralis) and flea beetles (Podagrica spp.). During the dry season, red spider mites (Tetranychus cinnabarinus) often attack the leaves. Control by spraying with recommended pesticides is rarely applied.
Jew’s mallow is very susceptible to root-knot nematodes (Meloidogyne spp.). Methods of control include crop rotation, avoiding other crops susceptible to root-knot nematodes for at least one year, and taking care to ensure a high organic matter content of the soil.
The first harvest by cutting shoots 20–30 cm long may take place 4–6 weeks after transplanting at a height of 10–20 cm above the ground. This cutting stimulates the development of side shoots. Subsequently every 2–3 weeks a cutting may take place, in total 2–8 cuttings. For a once-over harvest from a direct sown crop the plants are uprooted or cut at ground level when they are 30–40 cm tall, 3–5 weeks after emergence and before development of fruits. The plants are bundled for marketing. In intercropping systems farmers tend to harvest at irregular intervals. Wild Jew’s mallow is picked from the vegetation when required, usually for home consumption.
A crop planted for jute production is generally harvested 100–120 days after sowing when the plants are in the early fruit stage.
In Nigeria a yield of 20–25 kg per 10 m2 bed may be expected from 3–9 cuttings of ‘Amugbadu’ during a period of 3–4 months. In an experiment in Cameroon a yield of 38 t/ha was obtained from a well-fertilized field of cultivar ‘Ewondo’. Farmers however, usually obtain average yields of 5–15 t/ha.
The world average jute yield is about 1.9 t of raw fibre per ha, but yields of 5 t/ha have been obtained in Bangladesh with improved cultivars grown under optimal agronomic conditions.
Handling after harvest
Jew’s mallow leaves cannot be kept long. Mostly the product is sold on the harvest day, and it is constantly kept wet. If cooled to 20°C it can be kept for about 1 week, in cold storage for several weeks. If the leaves are dried and pounded to powder, the product can be kept for at least half a year.
Jute stems are retted in water for a period of (8–)15–20(–30) days to free the fibres from the bark. When retting is complete, the fibres are stripped manually from the stems, subsequently washed and dried, and then graded and packed.
The risk of genetic erosion is negligible because there is almost no commerce of seed of improved cultivars. At the Nigerian Horticultural Research Institute NIHORT at Ibadan, a collection of local types is maintained. The genebank of the Bangladesh Jute Research Institute in Dhaka has the mandate of world repository for germplasm of jute. It has a collection of almost 1500 Corchorus olitorius accessions through various germplasm collection projects in Asia and East Africa.
Farmers select the most vigorous plants with the best mucilaginous properties. When smaller leaves are required, farmers select for profuse branching. At NIHORT in Ibadan selections have been made for rapid early growth, large leaf size, dark green glossy leaves and late flowering. Hand crossing appeared difficult because of flower drop after emasculation.
Jute selection with the objectives of higher yield, finer fibre quality, disease resistance, early crop maturity and low photosensitivity has been practised for many years in Bangladesh and India and has resulted in several successful Corchorus olitorius cultivars.
Jew’s mallow is a high quality leafy vegetable in market value, consumers’ preference and nutritional value. Reliable seed of improved cultivars should become commercially available. It is recommended that local cultivars be collected and tested for useful characteristics including adaptation to various environments, resistance to diseases and yield. It seems impossible for Africa to compete in export markets for jute, in view of the excellent conditions for jute cultivation in Bangladesh and India.
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Sources of illustration
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Correct citation of this article:
Fondio, L. & Grubben, G.J.H., 2004. Corchorus olitorius L. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
wild and planted
1, flowering branch; 2, flower; 3, fruits; 4, seed.
Redrawn and adapted by Iskak Syamsudin
crop near a swamp
cv. ‘Géant de Bertoua’
shoot of ‘Incisifolius’ type of cultivar