Prota 2: Vegetables/Légumes
Preslia 46: 152 (1974).
Polygonum tomentosum Willd. (1799) non Schrank, Polygonum attenuatum R.Br. (1810), Polygonum pulchrum Blume (1826).
Watersmart weed, hairy knotweed (En).
Origin and geographic distribution
Persicaria attenuata is widespread in the tropics and subtropics of Africa, Asia and Australia. In Africa it is common in wet localities.
The leaves of Persicaria attenuata are locally (e.g. in Benin and Tanzania) used as a fresh salad or as a cooked vegetable and are also grazed by stock. In South-East Asia the leaves are eaten with food as a tonic and to purify the blood. Persicaria attenuata is widely used medicinally. In East Africa the leaves are used in treatments for syphilis, rheumatism and swellings. In southern Africa a decoction of creeping stems is applied to cattle suffering from black gall sickness. In DR Congo the plant is burnt to obtain a vegetable salt which is rich in potassium and is applied to sores on the back and chest of scrofulous hunchbacked children.
The nutritive value of Persicaria attenuata is not known; it may be similar to that of Persicaria decipiens (R.Br.) K.L.Wilson, which is also used as a vegetable in Africa. The rhizome contains 2.5% of an acrid resin which is a depressant and can arrest the heart.
Robust, hairy, rhizomatous perennial herb up to 2 m tall, with branched stems, basally creeping and rooting at the nodes, becoming hollow when older. Leaves alternate, simple; ocrea cylindrical, up to 4 cm long, surface coarsely villous, apex with a fringe of bristles; petiole up to 7 mm long; blade narrowly elliptical to narrowly ovate, 5–25 cm × 1–6 cm, pubescent, veins prominent below. Inflorescence a panicle of 2–5 spike-like racemes 5–8 cm long, usually leafless; peduncle stout, often in pairs; bracts ovate, 2–3 mm long, reddish, fringed terminally. Flowers bisexual, distinctly heterostylous; pedicel exceeding the bracts by 1–2 mm; perianth campanulate, 3–4.5 mm long, white or pink, lobes 4–5, oblong-elliptical, 2–3 mm long; stamens 5–8; ovary superior, 1-celled, styles 2, united at base, stigmas capitate. Fruit a lens-shaped nut, sometimes flattened on one side, 2–3 mm long, shiny black.
The taxonomy of Persicaria has not yet stabilized, at present comprising about 150 species. Most species have been described in the genus Polygonum, from which Persicaria is a segregate.
Persicaria attenuata is very variable and 3 subspecies have been distinguished, mainly based on hairiness of ocrea and leaf, and leaf and fruit form. Of these, subsp. africana K.L.Wilson is the only one in Africa. Subsp. attenuata occurs in South-East Asia and Australia and subsp. pulchra (Blume) K.L.Wilson in eastern Asia.
Persicaria attenuata grows in and beside water, often forming large patches with long floating stems that root at the lowest nodes, from sea-level up to 1000 m altitude. In Sierra Leone Persicaria attenuata is sometimes a troublesome weed in rice, although it is also considered an indicator of land suitable for rice cultivation.
Persicaria attenuata is collected from the wild and is not cultivated.
Genetic resources and breeding
Persicaria attenuata is very widespread and not in danger of genetic erosion.
Persicaria attenuata will remain a locally used vegetable and medicinal plant. More research is needed to verify its nutritional and medicinal value.
• Burkill, H.M., 1997. The useful plants of West Tropical Africa. 2nd Edition. Volume 4, Families M–R. Royal Botanic Gardens, Kew, United Kingdom. 969 pp.
• Decary, R., 1946. Plantes et animaux utiles de Madagascar. Annales du Musée Colonial de Marseille, 54e année, 6e série, 4e volume, 1er et dernier fascicule. 234 pp.
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• Ruffo, C.K., Birnie, A. & Tengnäs, B., 2002. Edible wild plants of Tanzania. Technical Handbook No 27. Regional Land Management Unit/ SIDA, Nairobi, Kenya. 766 pp.
• Wilson, K.L., 1990. Some widespread species of Persicaria (Polygonaceae) and their allies. Kew Bulletin 45(4): 621–636.
• Busson, F., 1965. Plantes alimentaires de l’ouest Africain: étude botanique, biologique et chimique. Leconte, Marseille, France. 568 pp.
• Cavaco, A., 1953. Polygonacées (Polygonaceae). Flore de Madagascar et des Comores (plantes vasculaires), famille 65. Firmin-Didot et cie., Paris, France. 22 pp.
• Graham, R.A., 1958. Polygonaceae. In: Turrill, W.B. & Milne-Redhead, E. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 40 pp.
• Hedberg, O., 2000. Polygonaceae. In: Edwards, S., Mesfin Tadesse, Demissew Sebsebe & Hedberg, I. (Editors). Flora of Ethiopia and Eritrea. Volume 2, part 1. Magnoliaceae to Flacourtiaceae. The National Herbarium, Addis Ababa University, Addis Ababa, Ethiopia and Department of Systematic Botany, Uppsala University, Uppsala, Sweden. pp. 336–347.
• Keay, R.W.J., 1954. Polygonaceae. In: Keay, R.W.J. (Editor). Flora of West Tropical Africa. Volume 1, part 1. 2nd Edition. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. pp. 137–142.
• Nguyen Thi Do, 2001. Persicaria Miller. 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. 412–415.
• Thulin, M., 1993. Polygonaceae. In: Thulin, M. (Editor). Flora of Somalia. Volume 1. Pteridophyta; Gymnospermae; Angiospermae (Annonaceae-Fabaceae). Royal Botanic Gardens, Kew, United Kingdom. pp. 175–179.
• van den Bergh, M.H., 1993. Minor vegetables. In: Siemonsma, J.S. & Kasem Piluek (Editors). Plant Resources of South-East Asia No 8. Vegetables. Pudoc Scientific Publishers, Wageningen, Netherlands. pp. 280–310.
• van der Zon, A.P.M. & Grubben, G.J.H., 1976. Les légumes-feuilles spontanés et cultivés du Sud-Dahomey. Communication 65. Département des Recherches Agronomiques, Koninklijk Instituut voor de Tropen, Amsterdam, Netherlands. 111 pp.
• Watt, J.M. & Breyer-Brandwijk, M.G., 1962. The medicinal and poisonous plants of southern and eastern Africa. 2nd Edition. E. and S. Livingstone, London, United Kingdom. 1457 pp.
Correct citation of this article:
Jansen, P.C.M., 2004. Persicaria attenuata (R.Br.) Soják In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.