Prota 2: Vegetables/Légumes
2n = 56
Flower of an hour, bladder hibiscus, bladder weed, bladder ketmia, Venice mallow, devil’s head in a bush, trailing hollyhock (En). Fleur d’une heure, ketmie d’Afrique (Fr).
Origin and geographic distribution
Hibiscus trionum occurs throughout the Old World tropics and subtropics, and even in temperate areas. In Africa it is only absent from the Guineo-Congolian rainforest zone. In the New World it was introduced and has become naturalized.
Young leaves, flowers and young shoots of Hibiscus trionum are eaten raw or cooked in Kenya, Zimbabwe, Australia and China. In Australia the root is considered edible although very fibrous. Hibiscus trionum is cultivated as an ornamental in the subtropics.
In South Africa an infusion is made of the ground shoot to clean wounds; it relieves pain and helps in drying the wound. It is also used against roundworm in Zimbabwe and South Africa, and as a stomachic in China. In eastern Sudan dry fruits are given to camels as a laxative. In India an infusion of the flowers is used to treat itch and painful skin problems, and as a diuretic. In southern Europe the leaf is used as an expectorant and to treat warts.
Cooked leaves of Hibiscus trionum are mucilaginous, without much flavour. The seeds contain 22–24% of oil and a small quantity of gossypol.
Annual herb up to 1.5 m tall; stem with stellate hairs or hispid. Leaves alternate, simple to deeply palmately 3–5-lobed; stipules linear, up to 8 mm long; petiole 1–4.5 cm long; blade orbicular to ovate in outline, up to 7.5 cm × 9 cm, base truncate to slightly cordate, lobes pinnately incised, margin serrate or slightly sinuate, hispid on veins, palmately veined. Flowers solitary, axillary, bisexual, regular, 5-merous; pedicel up to 5.5 cm long; epicalyx segments 10–12(–13), filiform, 7–14 mm long, apex entire; calyx campanulate, up to 2.5 cm long, becoming inflated, ribs of lobes purplish with stellate hairs or hispid; petals free, obovate, up to 3.5 cm × 3 cm, white, cream or yellow with purple base; stamens numerous, united into a column up to 4 mm long; ovary superior, 5-celled, style with 5 branches, included in the staminal column. Fruit an ovoid to globose capsule up to 1.5 cm long, hispid, enclosed in calyx, many-seeded. Seeds reniform, c. 2 mm × 3 mm, dark brown.
Hibiscus comprises 200–300 species, mainly in the tropics and subtropics. Although very variable in leaf shape and size of flowers, Hibiscus trionum is not likely to be confused with other species of the genus in Africa. It is classified in a separate section Trionum, characterized by its inflated, bladderlike calyx in fruit. Hibiscus mutabilis L., an introduced ornamental naturalized in parts of Africa, also has an inflated calyx but is a shrub with flowers 8–10 cm in diameter, white turning red by evening. Flowers of Hibiscus trionum only open when the sun shines and are short-lived. Cross- and self-pollination (delayed selfing) both occur.
Hibiscus trionum occurs in grassland, along roadsides and as a weed of arable crops, up to 2800 m altitude. In East Africa it is common on black cotton soils. The minimum, optimum and maximum temperatures for seed germination were found to be 10°C, 30°C and 40°C respectively.
Hibiscus trionum is a host of cucumber mosaic virus (CMV), whitefly (Bemisia tabaci) and spiny bollworm (Earias insulana).
Genetic resources and breeding
Several genebanks have accessions of Hibiscus trionum. As the species is widespread and abundant, it is not at risk of genetic erosion. Several improved ornamental cultivars have been released such as ‘Simply Love’ and ‘SunnyDay’.
Hibiscus trionum will remain a minor vegetable of only local importance. The widespread medicinal use in treating skin problems warrants pharmacological research.
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Correct citation of this article:
Bosch, C.H., 2004. Hibiscus trionum L. In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.