Prota 2: Vegetables/Légumes
2n = 72
Roselle, Jamaican sorrel, Indian sorrel, bissap, karkadeh (En). Roselle, oseille de Guinée, karkadé, bissap, thé rose d’Abyssinie, groseille pays (Fr). Vinagreira, azeda de Guiné, azedinha, caruru azedo, quiabeiro azedo (Po). Ufuta, ufuta dume (Sw).
Origin and geographic distribution
Hibiscus sabdariffa probably originates from Africa, where it may have been domesticated in Sudan about 6000 years ago, first for its seed and later for leaf and calyx production. In the 17th century vegetable types were introduced to India and the Americas. Selection for fibre production took place in Asia, where cultivation is reported from the beginning of the 20th century, e.g. in India, Sri Lanka, Thailand, Malaysia and Java. Roselle is now found throughout the tropics. In tropical Africa it is especially common in the savanna region of West and Central Africa. It is often found as an escape from cultivation. However, apparently truly wild plants of Hibiscus sabdariffa have been collected in Ghana, Niger, Nigeria and Angola.
In Africa roselle has two main uses: as a vegetable and for preparation of a beverage. Young roselle shoots, leaves and calices are used as a cooked vegetable or finely cut and used in sauces. The leaves and fresh green calices are used to make a soup, which is rather mucilaginous in texture. Freshly harvested leaves and/or calyces are also added to water-based sauces; oil, salt, onions, dried fish and hot pepper are often added. The sauces are eaten with tuber or cereal porridges or rice. Green roselle types are more appreciated for use as a cooked vegetable than red types, which are more commonly used in sauces. In some areas the leaves are mixed with groundnut or sesame paste. The stewed calyces of the green type are added as a condiment (‘bëkëj’) to rice dishes in Senegal. In the United States leaves and young shoots are also eaten raw in salads and the red fleshy calyx lobes are chopped and used in fruit salads, but these uses are not common in Africa. In Côte d’Ivoire the dried calyces ground to powder are used in sauces during the dry season.
The dried red calyces are commonly used to prepare a tea, drunk hot or, more commonly, cold after adding sugar. It is a sour tasting, refreshing drink, very popular from Senegal to Sudan and in Egypt and other northern African countries where it is referred to as ‘karkadé’. Juice is often sold chilled or frozen as ‘bissap’ (Senegal) or ‘da bilenni’ (Côte d’Ivoire, Mali, Burkina Faso) along highways and in urban markets. Mint or ginger is sometimes added when boiling the calyces, particularly if the juice is to be sold frozen. The calyces are also boiled down to make a syrup concentrate. Due to their high inherent pectin content, roselle jams and jellies are also popular, particularly in Senegal, the Caribbean region and southern Asia. The dried calyces are used in Western countries as a base for many herbal teas and as a source of red food colorants. Following calyx harvest in West Africa, roselle plants are often used as fodder for livestock.
The oil of roselle seed is extracted and used for cooking, e.g. in Chad, Tanzania and China. However, the seed oil is claimed to contain some toxic substances and may be better used in the soap and cosmetics industries. Locally, the seeds are eaten roasted as a snack or ground into meal. In the Plateau region of Nigeria people ferment roselle seeds to make a cake used as ‘sorrel meat’. The oil is also used as an ingredient of paints.
Roselle tea is used to suppress high blood pressure. The leaves are a source of mucilage used in pharmacy and cosmetics. Extracts are often used medicinally to treat colds, toothache, urinary tract infections and hangovers. Leaf juice is used to treat conjunctivitis in Senegal. Leaves are applied as a poultice to treat sores and ulcers. A root decoction can be used as a laxative.
As in Asia, roselle fibre is locally used in West Africa, but on a very small scale. The bast fibre is a good substitute for jute and it is used for making twine, cordage, rope, netting and sacks. The bast fibre and sometimes also the whole stem are used in the paper industry in the United States and Asia. The ornamental value of roselle is of recent interest, as a garden plant or cut flower. The decorative red stalks with ripe red fruits are exported to Europe where they are used in flower arrangements.
Production and international trade
Roselle is an important leafy vegetable in the drier parts of West and Central Africa. In Senegal, Mali, Chad and Sudan large quantities of calyces are produced for the preparation of beverages. Sudan is the major country in tropical Africa producing dried roselle calyces for local consumption and export, mainly in the Kordofan and Darfur regions in the west of the country. Production of roselle leaves and calyces for domestic consumption in Africa has not been quantified, although these are common products on local markets.
International trade of roselle calyces has increased steadily over the last decades, with 15,000 t/year now entering the world market. Germany and the United States are large importers. In 1998, United States and German importers paid 1200–1700 US$/t for Egyptian and Sudanese roselle; prices of Chinese roselle were lower. Prices fluctuate due to high variability in supply. A decrease in product quality in Thailand and China due to excessive precipitation caused world prices to soar to 4000 US$/t in 2003.
Sudan is the most important roselle producer in Africa, the annual area fluctuating between 11,000 ha and 57,000 ha depending on the amount of rainfall and prices. In 1995 Sudan reported exports of 32,000 t. In Sudan smallholder farmers traditionally grow roselle in plots ranging from under 0.25 ha to 2 ha, but some growers have up to 20 ha. Sudanese roselle is viewed as superior quality, but the United States trade embargo and large -scale production in Mexico, Thailand and China has led to shifts in the market. Jamaica and Egypt also export roselle. Senegal and Mali are also major producers, but the vast majority of their production is for domestic consumption or sold on the local markets. Fluctuations in export prices for cash crops such as cotton have led many West African farmers to diversify production, e.g. by growing roselle for the domestic market. In Asia roselle is primarily a fibre crop, accounting for 20% of jute-like fibre production or 700,000 t/year.
The nutritional composition of roselle leaves per 100 g edible portion is: water 85.6 g, energy 180 kJ (43 kcal), protein 3.3 g, fat 0.3 g, carbohydrate 9.2 g, dietary fibre 1.6 g, Ca 213 mg, P 93 mg, Fe 4.8 mg, β-carotene 4135 μg, thiamin 0.2 mg, riboflavin 0.45 mg, niacin 1.2 mg, ascorbic acid 54 mg. The composition of fresh raw calyces per 100 g edible portion is: water 86.2 g, energy 184 kJ (44 kcal), protein 1.6 g, fat 0.1 g, carbohydrate 11.1 g, fibre 2.5 g, Ca 160 mg, P 60 mg, Fe 3.8 mg, β-carotene 285 μg, thiamin 0.04 mg, riboflavin 0.06 mg, niacin 0.5 mg, ascorbic acid 14 mg. The nutritional composition of the seed per 100 g edible portion is: water 8.2 g, energy 1721 kJ (411 kcal), protein 19.6 g, fat 16.0 g, carbohydrate 51.3 g, dietary fibre 11.0 g, Ca 356 mg, P 462 mg, Fe 4.2 mg, thiamin 0.1 mg, riboflavin 0.15 mg, niacin 1.4 mg, ascorbic acid trace (Leung, W.-T.W., Busson, F. & Jardin, C., 1968).
The dried red calyces contain organic acids, sugars and anthocyanin pigment. They are high in citric, malic and ascorbic acids. Roselle seed oil has properties similar to cotton seed oil and contains linoleic, oleic, palmitic and stearic acids as major fatty acids. A number of exceptional fatty acids, e.g. epoxy oleic acid and the cyclopropene acids sterculic acid and malvalic acid, have been reported in the seed oil. Seed proteins are mostly globulins, highly soluble at acidic and alkaline pH levels.
Roselle has antispasmodic, anthelminthic and bactericidal properties. The antihypertensive and cardioprotective effects of tea made from roselle calyces have been demonstrated in various animal tests, and also in a few clinical tests. The phenolic compound protocatechuic acid isolated from roselle flowers showed antioxidant, antitumour and hepatoprotective activities. Roselle extracts also showed antipyretic and anodyne properties in tests with mice. The seed oil exhibits antibacterial and antifungal activities.
Roselle produces a bast fibre similar to jute (Corchorus capsularis L. and Corchorus olitorius L.), except that it is whiter and somewhat coarser. The raw retted and dried fibre makes up about 5% and the dry wood 18% of the freshly harvested and defoliated green stems. The commercial fibre has a length of up to 2.1 m. The bast fibre cells are (1.2–)1.9–3.1(–6.3) mm long and (10–)12–25(–44) μm wide, with maximum length and width in the middle portion of the stem. Lumen width and cell wall thickness vary from 3–15 μm and (4–)8–15 μm, respectively. Most fibre cells have tapering rounded ends. The wood consists of fibre cells 0.5–1.0 mm long and about 24–26(–32) μm wide, with a lumen width of 9 μm and a cell wall thickness of 3–7 μm. The bast fibres contain about 32% α-cellulose, 10–15% lignin and 1% ash.
Adulterations and substitutes
Leaves of other Hibiscus spp., e.g. kenaf (Hibiscus cannabinus L.) and false roselle (Hibiscus acetosella Welw. ex Hiern) can be used as substitutes for roselle. They are sometimes even sold together.
Large annual herb up to 4.5 m tall; stem glabrous to sparsely pubescent, sometimes sparsely prickly, green or reddish. Leaves alternate, simple; stipules narrowly lanceolate to linear, up to 1.5 cm long; petiole 0.5–12 cm long; blade shallowly to deeply palmately 3–5(–7) -lobed, sometimes undivided, up to 15 cm × 15 cm, margin toothed, glabrous or sparsely pubescent, sometimes with a few prickles on midrib, palmately veined, with a distinct nectary at base of midrib. Flowers solitary in leaf axils, bisexual, regular, 5-merous; pedicel up to 2 cm long, articulate; epicalyx segments 8–12, united at base, subulate to triangular, free part 0.5–2 cm long; calyx campanulate, up to 5.5 cm long, becoming fleshy in fruit, lobes nearly glabrous to hispid hairy, with a nectary outside; petals free, obovate, up to 5 cm × 3.5 cm, pale yellow or pale pink, often with dark red-purple centre; stamens numerous, united into a column up to 2 cm long, pink; ovary superior, 5-celled, style with 5 branches. Fruit an ovoid capsule up to 2.5 cm long, almost glabrous to appressed-pubescent, enclosed by the calyx, many-seeded. Seeds reniform, up to 7 mm long, dark brown. Seedling with epigeal germination; cotyledons rounded, up to 2.5 cm × 3 cm, leafy.
Other botanical information
Hibiscus comprises 200–300 species, mainly in the tropics and subtropics; many of them grown as ornamentals. The estimated number of species varies because opinions differ about inclusion of several related groups of species in the genus. Hibiscus sabdariffa belongs to section Furcaria, a group of about 100 species which have in common a pergamentaceous calyx (rarely fleshy) with 10 strongly prominent veins, 5 running to the apices of the segments and bearing a nectary, and 5 running to the sinuses. Other species belonging to this section and used as a vegetable are Hibiscus acetosella Welw. ex Hiern, Hibiscus asper Hook.f., Hibiscus cannabinus L., Hibiscus diversifolius Jacq., Hibiscus mechowii Garcke, Hibiscus noldeae Baker f., Hibiscus rostellatus Guill. & Perr. and Hibiscus surattensis L.
Two main types of cultivated Hibiscus sabdariffa are distinguished, originally described as botanical varieties: var. sabdariffa with a bushy, strongly branching habit and glabrescent calyx, accrescent and becoming fleshy in fruit; and var. altissima Wester with taller, usually unbranched habit and often hispid hairy calyx, hardly accrescent and not fleshy in fruit. The latter is grown for its fibre, and not common in Africa. These types can best be regarded as cultivar-groups.
Hundreds of cultivars grown as vegetable or for their calyces exist. In some of these anthocyanins are present, resulting in reddish stems, leaves and calyces, and pinkish petals, whereas in others anthocyanins are absent, and these have green stems and leaves, pale green calyces and pale yellow petals.
Growth and development
The vegetative growth period lasts from 4 months to 6 months. Plant height 30 days after emergence of the seedlings is about 30 cm. Leaf harvest may start 6–8 weeks after sowing; it stimulates branching and subsequently increases leaf production. Flowering begins when daylength decreases, at the earliest 2 months after sowing, and at the latest 7 months. The flowers are ususally self-pollinating. Two or three months after pollination fruits may begin to ripen.
Roselle has temperature requirements ranging between 18ºC and 35ºC. Plant growth stops at 14°C, with death occurring after 15 days. At 10°C, death occurs after only 2–3 days. Flower and calyx production is reduced at temperatures below 17°C. Cotyledons cannot withstand temperatures below 10°C for more than 2–3 hours.
Roselle is a photoperiod sensitive plant that flowers best when the daylength is shorter than 12 hours. It requires 13 hours/day light during vegetative growth to prevent premature flowering. Having a deep root system, roselle requires adequate soil depth and is rather drought resistant. The crop can grow in a wide range of soil types, the best being retentive, friable loams. Roselle thrives in areas receiving 800–1600 mm of continuous annual rainfall, and requires a minimum of 100–150 mm/month during vegetative growth, or 300–400 mm distributed over a period of 3–4 months. Dry periods during the final months of growth promote good calyx production, while excess precipitation or humidity can lower the quality of the calyces. Roselle plants with anthocyanin pigmentation are able to withstand the harsh Sahelian environment better than plants with a yellow-green colour.
Apparently wild types of Hibiscus sabdariffa are found in savanna grassland and open woodland.
Roselle grown in home gardens as a leafy vegetable or for leaves and calyces is cultivated under irrigation, mostly done manually with watering cans. It is given normal garden management. When grown as a field crop for calyces little care is generally given unless grown in intercropping. It then benefits from the care given to the main crop. Roselle responds well to fertilizers. In Egypt ammonium sulphate has been reported to result in higher yields than calcium nitrate or urea. Calyx production is greater when plants are fertilized at thinning (20–30 days after planting) than when the applications are split and given during the vegetative stage and at flowering. However, chemical fertilizers are rarely applied in tropical Africa as they are too costly under the uncertain climatic conditions where roselle is grown. A few t per ha of dry organic manure is sometimes applied. Smallholder farmers regard roselle as a low-input, low-labour crop. Weeding is rarely practised, but if done it results in higher calyx yields. Better calyx yields were observed when roselle is intercropped, particularly with a legume planted two weeks after establishment of the roselle crop.
In Thailand and India roselle for fibre is grown as a rainfed crop. A single round of weeding and thinning is usually performed 20–30 days after planting. The recommended fertilizer dose is 15 kg N, 15 kg P and 15 kg K per ha given after weeding.
Propagation and planting
Roselle is grown both as a rainfed field crop and as an irrigated garden vegetable. As leafy vegetable, seeds are either broadcast or dibbled with 3–5 seeds/hole, 2–3 cm deep, at an average spacing of 40–60 cm in rows and 60–90 cm between rows. The 1000-seed weight is (15–)25–28 g. For calyx production, the spacing should be wider, up to 100 cm apart. In Senegal vegetable farmers use 15–25 kg seed per ha for calyx production, whereas research recommends only 4–8 kg. Some growers sow in a shaded nursery, and transplant into the field after about 4 weeks. For fibre production, seeds are drilled more closely, at 15 cm × 20 cm or 10 cm × 30 cm. Because roselle is deep rooting, deep ploughing is recommended for heavier soils. In sandy soils shallow ploughing is common.
Rainfed roselle crops are sown at the beginning of the rainy season. In the Sahel region year-round planting is possible with irrigation. Roselle is often intercropped with other crops such as pearl millet, sorghum, groundnut, sweet potato, yam or cowpea, and spontaneous roselle plants are often allowed to grow amongst other crops. Many farmers plant roselle along field boundaries or to delineate sub-plots within a field. In West Africa roselle is also grown as part of a parkland agroforestry system, in conjunction with e.g. apple-ring acacia (Faidherbia albida (Delile) A.Chev.), baobab (Adansonia digitata L.), African locust bean (Parkia biglobosa (Jacq.) R.Br. ex G.Don, shea butter tree (Vitellaria paradoxa C.F.Gaertn.) and jujube (Zizyphus mauritania Lam.).
Diseases and pests
Roselle is susceptible to most diseases affecting cotton, and root and stem rot caused by several Phytophthora spp. lead to plant losses. Phytophthora nicotianae var. parasitica causes stem burn (also called collar rot or stem canker), causing purplish black discoloration encircling the stem 30 cm above the ground and sudden wilting of the plant. Resistance has been found in fibre-type roselle cultivars. Unlike its close relative kenaf, roselle is susceptible to infection by Coniella musaiaensis var. hibisci. Plant and calyx senescence due to this pathogen have been observed in Central Africa, Nigeria, the Caribbean region and India. Irregular, pale brown lesions appear on lower leaves increasing in size, bleaching the leaf surface and ultimately resulting in necrosis of tissue. Brown stem lesions may also develop. Leaf spot caused by Cercospora hibisci is also common. Roselle types with green leaves are susceptible to powdery mildew (Oidium abelmoschi), types with red leaves are partially resistant. A virus disease is reported from Nigeria, causing hard cracking leaves. Roselle is rather resistant to root-knot nematodes (Meloidogyne spp.), but not to free-living nematodes (Heterodera spp.).
Pressure from insect pests is high. Cotton bollworm larvae (Earias biplaga, Earias insulana) are very damaging as they bore into the unripe fruits. The larvae of flea beetles (Podagrica spp.) feed on the roots and the adults damage leaves and growing points. The cotton stainer (Dysdercus superstitiosus) sucks on the calyces, causing brown spots. Infestation by spiral borers (Agrilus acutus) can lead to galls on the stems, approximately 5 cm in length and leading to some reduction in nutrient uptake. However, research in Bangladesh has demonstrated roselle to be much more resistant to infestation than kenaf. Other pests are cutworm, mealy bugs, leaf hoppers and snails. Attacks by insect pests can be reduced by beneficial predators, e.g. it was observed that jassids (Amrasca biguttula) were predated by 8 species of spiders. Similarly, Hibiscus sabdariffa has helped reduce pest populations in intercropped systems, e.g. infestation of bean (Phaseolus vulgaris L.) by several white fly species was reduced by intercropping with roselle, due to increased hyperparasite diversity.
The first harvest comprises seedlings collected during thinning. When the plants are 6–8 weeks old, branches of about 50 cm long are picked 2 or 3 times during the period of vegetative growth. Calyces are harvested manually 2–3 weeks after flowering, usually 4–6 months after sowing, before the fruit has dried and dehisced. Regular picking prolongs flowering. The calyces are dried in the shade. When harvested for fibre, stems are cut before flowering, 4–5 months after planting. Fibre quality declines rapidly after the start of flowering.
For leafy branches yields of up to 20 t/ha from three cuttings have been reported. Fresh calyx yields range from 4–6.5 t/ha, or about 800–1200 kg/ha when dried to 12% moisture content. In Asia fresh calyx yields of up to 15 t/ha have been reported. A single roselle plant may yield as many as 250 calyces, or 1–1.5 kg fresh weight. In Africa average yields are much lower and variable because of environmental conditions and extensive management. Sudan reports an average yield of dry calyces of 93 kg/ha. In Senegal maximum production of calyx on a dry weight basis is 500 kg/ha.
Average fibre yields from roselle are 1.5–2.5 t/ha, depending on cultivar and management. India reported an average yield of 1.9 t/ha for 1997–2001. Reported seed yields range from 200–1500 kg/ha.
Handling after harvest
As a leafy vegetable roselle shoots are sold in bunches with a length of up to 50 cm. Thinned seedlings are less perishable than shoots; as they are sold with their roots attached they can be kept fresh by placing the roots in water.
In most areas in Africa roselle calyces are air dried prior to marketing. Drying in the sun can lead to reduced quality. Adequate ventilation is important. Plastic sheets are placed on the ground to avoid contamination with soil, which also strongly reduces the value. Drying by artificial heating is capital-intensive and rare in sub-Saharan Africa. Temperatures must remain below 43°C.
Dried calyces are gathered and sold in bulk or in individual sachets throughout West Africa. In Senegal dried calyces are rolled into 80 kg balls for export. Roselle exported to the United States and Germany must meet strict standards concerning moisture content (maximum 12%), acidity, residues and contaminations.
To make roselle syrup, dried calyces are boiled at a ratio of 1 part dried roselle to 4–5 parts water. Because of its very tart taste, large amounts of sugar are added. The mixture is boiled down for several hours. Before use the syrup is watered down to make ‘da bilenni’. A study estimated that one person could produce about 300 l juice per day from 4 kg calyces.
For the production of fibre, harvested stems are soaked in water for two weeks, and then stripped of bark. Stems are then beaten to separate the fibres, which are washed, dried, and sorted into one of three levels of quality, based on length, colour, stiffness and purity. In some parts of Africa roselle seeds are ground into meal for addition to cereals, or seeds are roasted and boiled as a coffee substitute. Oil is extracted by parching the seeds, soaking in water made alkaline with ashes, and pounding them. The residue is sometimes eaten in soup or blended with bean meal to make fried snacks.
Local cultivars of roselle are common throughout semi-arid Africa. Although many smallholder farmers separate seeds by cultivar, stocks are generally heterogeneous. Roselle planted by traditional farmers in Sudan is usually of several different types and cultivars. Around 50 accessions from the local genetic resources in Sudan are preserved in the genebank of the Plant Genetic Resources Unit of the Agricultural Research Corporation, Wad Medani, Sudan. Characterization of some of these accessions revealed variation in stem colour, leaf shape and calyx shape, colour and size. A practical classification used in Sudan for the many beverage strains is on the basis of calyx characteristics. The calyx lobes may be thick, curved outwards and easy to peel; or long, bending inwards, enclosing the fruit and easy to peel; or thin, tightly enclosing the fruit and difficult to peel; or bell shaped with well-developed epicalyx. In Senegal farmers distinguish between 7 ‘bissap’ types, 3 green types and 4 red ones. The distinctive characters used to identify the ‘bissap’ types include colour, size and shape of leaves and fruits. Seeds of ‘bissap’ germplasm in Senegal are stored at the Seed Production Unit, Horticultural Development Centre (CDH), Dakar. Other germplasm collections of Hibiscus sabdariffa are held at Jute Research Institute, Dhaka, Bangladesh (320 accessions), USDA Southern Regional Plant Introduction Station, Griffin GA, United States (95 accessions), Central Research Institute for Jute and Allied Fibres, Barrackpore, India (75 accessions) and National Horticultural Research Institute, Ibadan, Nigeria (11 accessions).
Roselle breeding has hitherto received little attention hitherto. The Sudanese cultivar ‘El Rahad’ is considered superior in quality for calyx production. Breeding objectives of roselle in Sudan include purification of local cultivars and selection for better yield and calyx quality. In Senegal the objectives of the breeding programme include the improvement of leaf yield of green cultivars, and the improvement of yield and taste of cultivars suited for calyx production. Seed company Technisem markets seed of cultivar ‘Bissap Koor Rouge’, suitable for use as leafy vegetable and for calyx production, and tolerant of nematodes and heat.
Roselle is an underutilized multipurpose crop providing farmers with food and cash income when other vegetables have become scarce. Processing generates additional family income, from which women benefit in particular. Use of roselle as a vegetable or as a beverage should be promoted through research to improve cultivars, husbandry and post-harvest technologies. Applying rigorous quality standards for grading, processing and packaging will boost competitiveness in the international market. Demand for roselle fibre is likely to increase as a result of the rising interest in natural, biodegradable fibres.
• Boonkerd, T., Na Songkhla, B. & Thephuttee, W., 1993. Hibiscus sabdariffa L. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 178–180.
• Dupriez, H. & De Leener, P., 1987. Jardins et vergers d’Afrique. Terres et Vie, Nivelles, Belgium. 354 pp.
• FAO, 1988. Traditional food plants: a resource book for promoting the exploitation and consumption of food plants in arid, semi-arid and sub-humid lands of Eastern Africa. FAO food and nutrition paper 42. Food and Agriculture Organization, Rome, Italy. 593 pp.
• FAO-AGSI, 1999. Post-Harvest Compendium. [Internet]. FAO, Rome, Italy. http://www.fao.org/inpho/compend/text/ch28/ch28.htm. Accessed June 2004.
• Morton, J.F. & Dowling, C.F., 1987. Fruits of warm climates. [Internet] Julia F. Morton, Miami, United States. 505 pp. http://www.hort.purdue.edu/newcrop/morton/roselle.html. Accessed June 2004.
• 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.
• Seck, A., Sow, I. & Niass, M., 1999. Senegal. In: Chweya, J.A. & Eyzaguirre, P.B. (Editors). The biodiversity of traditional leafy vegetables. IPGRI, Rome, Italy. pp. 83–110.
• Shamsuddin Ahmad & van der Vossen, H.A.M., 2003. Hibiscus sabdariffa L. In: Brink, M. & Escobin, R.P. (Editors). Plant Resources of South-East Asia No 17. Fibre plants. Backhuys Publishers, Leiden, Netherlands. pp. 162–167.
• Undang A. Dasuki, 2001. Hibiscus 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. 297–303.
• van Epenhuijsen, C.W., 1974. Growing native vegetables in Nigeria. FAO, Rome, Italy. 113 pp.
• Adamson, W.C. & Monton, N.A., 1982. Stem and root density in kenaf and roselle at different harvest dates (Hibiscus cannabinus, Hibiscus sabdariffa) for best fiber, as annual sources of paper pulp. Crop Science 21: 849–851.
• Ahmad, S. & Faruquzzaman, A.K.M., 2000. Field evaluation of kenaf, mesta, and related genera for their reaction to spiral borer. Tropical Agriculture 77: 232–235.
• Akindahunsi, A.A. & Olallleye, M.T., 2003. Toxicological investigation of aqueous-methanolic extract of the calyces of Hibiscus sabdariffa L. Journal of Ethnopharmacology 89: 161–164.
• Babatunde, F.E., 2003. Intercrop productivity of roselle in Nigeria. Journal of Tropical Crop Science and Production 11(1): 102–104.
• Diouf, M., Diop, M., Lo, C., Drame, K.A., Sène, E., Ba, C.O., Guèye, M. & Faye, B., 1999. Sénégal. In: Chweya, J.A. & Eyzaguirre, P.B. (Editors). The biodiversity of traditional leafy vegetables. IPGRI, Rome, Italy. pp. 111–154.
• El-Adawy, T.A. & Khalil, A.H., 1994. Characteristics of roselle seeds as a new source of protein and lipid. Journal of Agriculture & Food Chemistry 42: 1986–1900.
• El-Gamal, S.A., Omar, F.A. & Mahmoud, M.M., 1997. Effect of nitrogen fertilization on the growth and yield of Hibiscus sabdariffa L. Acta Horticulturae 144: 135–144.
• Katende, A.B., Ssegawa, P. & Birnie, A., 1999. Wild food plants and mushrooms of Uganda. Technical Handbook No 19. Regional Land Management Unit/SIDA, Nairobi, Kenya. 490 pp.
• Lakshminarayana, A., Murty, R.K., Rao, M.R. & Rao, P.A., 1980. Efficiency of nitrogen utilization by roselle and kenaf (Hibiscus sabdariffa, Hibiscus cannabinus). Indian Journal of Agricultural Science 50: 244–248.
• Leung, W.-T.W., Busson, F. & Jardin, C., 1968. Food composition table for use in Africa. FAO, Rome, Italy. 306 pp.
• McCaleb, R., 2000. Roselle production manual (Hibiscus sabdariffa). [Internet]. ASNAPP, Herb Research Foundation, Boulder CO, United States. http://www.herbs.org/africa/hibiscus_production_manual.html. Accessed June 2004.
• Nishimura, N., Izumi, A. & Kuroda, K., 2002. Structural properties of kenaf lignin: differences among kenaf varieties. Indian Crop Production 15: 115–122.
• Persad, C. & Fortune, M., 1989. A new disease of sorrel (Hibiscus sabdariffa var. sabdariffa) caused by Coniella musaiaensis var. hibisci from Trinidad and Tobago. Plant Pathology 38: 615–617.
• Rao, P.R.M., Raju, A.K., Rao, R.V.A. & Rao, B.H.K.M., 1980. Note on a new record of spider predators of Amrasca biguttula biguttula Ishida, a serious pest on mesta. Indian Journal of Agricultural Science 51: 203–204.
• Sarojini, G., Rao, K.C., Tulpule, P.G. & Lakshminarayana, G., 1985. Effects of processing on physicochemical properties and fatty acid composition of Hibiscus sabdariffa seed oil. Journal of the American Oil Chemists’ Society 62: 728–730.
• Stevels, J.M.C., 1990. Légumes traditionnels du Cameroun: une étude agrobotanique. Wageningen Agricultural University Papers No 90-1. Wageningen University, Wageningen, Netherlands. 262 pp.
• Thakur, R.N., Pandotra, V.R. & Sastry, K.S.M., 1977. Stem burn - a new disease of Hibiscus sabdariffa from India (Phytophthora nicotianae var. nicotianae). Indian Phytopathology 29: 322–323.
• Wilson, F.D., 1999. Revision of Hibiscus section Furcaria (Malvaceae) in Africa and Asia. Bulletin of the Natural History Museum, Botany Series 29: 47–79.
• Wolfson, D., Marani, A. & Steinitz, B., 1987. Chilling sensitivity of roselle. HortScience 22: 954.
Sources of illustration
• Boonkerd, T., Na Songkhla, B. & Thephuttee, W., 1993. Hibiscus sabdariffa L. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 178–180.
Correct citation of this article:
McClintock, N.C. & El Tahir, I.M., 2004. Hibiscus sabdariffa L. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.
1, flowering and fruiting shoot; 2, flower; 3, fruit enclosed by calyx.
young fruits of the vegetable type
fruit enclosed by calyx
fruits on the marktet
variety with fleshy calyx used for preparing tea