Prota 2: Vegetables/Légumes
Preslia 46: 155 (1974).
Polygonum senegalense Meisn. (1826).
Silver snake root (En).
Origin and geographic distribution
Persicaria senegalensis is widespread in tropical and subtropical Africa, including South Africa and Madagascar.
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.
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.
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.
Persicaria senegalensis grows in damp localities, along lake shores and streams, and in swamps, at 400–3000 m altitude.
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.
Persicaria senegalensis is an interesting species, meriting more research to evaluate its nutritional, medicinal and ornamental values.
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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.