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Persicaria senegalensis (Meisn.) Soják

Protologue
Preslia 46: 155 (1974).
Family
Polygonaceae
Synonyms
Polygonum senegalense Meisn. (1826).
Vernacular names
Silver snake root (En).
Origin and geographic distribution
Persicaria senegalensis is widespread in tropical and subtropical Africa, including South Africa and Madagascar.
Uses
The tender leaves of Persicaria senegalensis are eaten cooked as a vegetable. Only in times of drought it is grazed by livestock. In Kenya and DR Congo the plant is burnt to make a vegetable salt. In Senegal a leaf decoction is taken in draught and by enema to treat syphilis in a mixture with other plants. In Nigeria and Ethiopia pounded leaves are applied to swellings, syphylitic sores or skin affections; in Tanzania pounded roots are used in the same way. The plant is also used as a veterinary medicine in Madagascar and elsewhere. In Tanzania a black dye is prepared from the roots. Persicaria senegalensis has potential as an aquatic ornamental.
Properties
A chemical analysis of leaves of Persicaria senegalensis is not available, but the nutritive value may be similar to that of Persicaria decipiens (R.Br.) K.L.Wilson. The roots are said to be toxic. An abundance of saponins is present in the leaves. A crude water extract of the plant killed the freshwater snails Lymnae natalensis and Biomphalaria pfeifferi.
Botany
Erect perennial herb up to 3 m tall, glabrous to white-tomentose, with brown, striate stem inflated just above the nodes and rooting at lower nodes. Leaves alternate, simple; ocrea cylindrical, up to 4 cm long, membranous, glabrous, not fringed; petiole 1–7 cm long; blade lanceolate, up to 30 cm × 8 cm, tapering at both ends, lower surface with numerous small glands and often strigose on the midrib and along the edges. Inflorescence a panicle of 1–several spike -like racemes up to 10 cm long; peduncle with orange glands; bracts ovate-truncate, 3 mm long, usually with fringed margin. Flowers bisexual; perianth campanulate with 4–5 lobes c. 3 mm long, pink, greenish or white, gland-dotted; stamens 4–5; ovary superior, 1-celled, styles 2. Fruit a lens-shaped nut 2.5–3.5 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 senegalensis is variable in its indumentum, from glabrous to densely white woolly tomentose. This has resulted in the distinction of several subspecies, varieties and forms, but numerous intermediate types exist, sometimes even on the same plant. Persicaria senegalensis much resembles Persicaria glabra (Willd.) M.Gómez, but it is usually larger, leaves are wider and have a strigose midrib, its perianth is longer and its fruit never triangular. In Madagascar the leaves of Persicaria glabra are also used as a vegetable.
Ecology
Persicaria senegalensis grows in damp localities, along lake shores and streams, and in swamps, at 400–3000 m altitude.
Management
Persicaria senegalensis is not cultivated and only collected from the wild.
Genetic resources and breeding
Persicaria senegalensis is widespread and not in danger of genetic erosion.
Prospects
Persicaria senegalensis is an interesting species, meriting more research to evaluate its nutritional, medicinal and ornamental values.
Major references
• 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.
• Dossaji, S.F., Kairu, M.G., Gondwe, A.T. & Ouma, J.H., 1977. On the evaluation of the molluscidal properties of Polygonum senegalense forma senegalense. Lloydia 40: 290–293.
• 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.
• Wilson, K.L., 1990. Some widespread species of Persicaria (Polygonaceae) and their allies. Kew Bulletin 45(4): 621–636.
Other references
• Cavaco, A., 1953. Polygonacées (Polygonaceae). Flore de Madagascar et des Comores (plantes vasculaires), famille 65. Firmin-Didot et cie., Paris, France. 22 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.
• 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.
• Jansen, P.C.M., 1981. Spices, condiments and medicinal plants in Ethiopia, their taxonomy and agricultural significance. Agricultural Research Reports 906. Centre for Agricultural Publishing and Documentation, Wageningen, Netherlands. 327 pp.
• Kerharo, J. & Adam, J.G., 1974. La pharmacopée sénégalaise traditionnelle. Plantes médicinales et toxiques. Vigot & Frères, Paris, France. 1011 pp.
• Kokwaro, J.O., 1993. Medicinal plants of East Africa. 2nd Edition. Kenya Literature Bureau, Nairobi, Kenya. 401 pp.
• Odei, M.A., 1973. Observations on some weeds of malacological importance in the Volta Lake. Bulletin de l'Institut Fondamental d'Afrique noire 35A: 57–66.
• Raponda-Walker, A. & Sillans, R., 1961. Les plantes utiles du Gabon. Paul Lechevalier, Paris, France. 614 pp.
• Raynal-Roques, A., 1978. Les plantes aquatiques alimentaires. Adansonia séries 2, 18(3): 327–343.
• 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.
Author(s)
P.C.M. Jansen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands


Editors
G.J.H. Grubben
Prins Hendriklaan 24, 1401 AT Bussum, Netherlands
O.A. Denton
National Horticultural Research Institute, P.M.B. 5432, Idi-Ishin, Ibadan, Nigeria
Associate Editors
C.-M. Messiaen
Bat. B 3, Résidence La Guirlande, 75, rue de Fontcarrade, 34070 Montpellier, France
R.R. Schippers
De Boeier 7, 3742 GD Baarn, Netherlands
General editors
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands
L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article:
Jansen, P.C.M., 2004. Persicaria senegalensis (Meisn.) Soják In: Grubben, G.J.H. & Denton, O.A. (Editors). PROTA 2: Vegetables/Légumes. [CD-Rom]. PROTA, Wageningen, Netherlands.