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Origin and Habitat: Mozambique, Zambia, Zimbabwe, Swaziland, and South Africa (Eastern Cape, Free State, Gauteng, KwaZulu-Natal, Limpopo, Mpumalanga, Western Cape).
Altitude range: From near sea level up to 1800 metres.
Habitat and ecology: Dioscorea sylvatica grows in a variety of wooded and relatively mesic places, such as the moister bushveld areas, margins of forests, bracken or ericoid scrubs, Albany thicket, fynbos, grasslands, savanna, coastal bush and wooded mountain kloofs. It is quite frequent where it occurs but very slow growing (generation length estimated to be 30 years). There was a huge population decline from 1955-1960 as a result of indiscriminate commercial harvesting for diosgenin, a substance that was used to manufacture cortisone and other steroid hormones. Exploitation of tubers for the local medicinal plant trade is ongoing, and is preventing recovery. It is also threatened by the extreme pressure of pastoral grazing that is is changing the micro-habitat of the bush and possibly the decline of mature individuals is also caused by illegal overcollection of the tubers that are highly sought after by cudiciform collectors.
Dioscorea sylvatica Eckl.
S. African Quart. J. 1: 363 (1830)
- Dioscorea sylvatica Eckl.
- Testudinaria sylvatica (Eckl.) Kunth
- Dioscorea hederifolia Griseb.
- Dioscorea junodii Burtt Davy
- Dioscorea montana var. glauca R.Knuth
- Dioscorea montana var. lobata Weim.
- Dioscorea montana var. paniculata (Kuntze) R.Knuth
- Dioscorea montana var. sagittata Suess.
- Dioscorea sylvatica var. brevipes (Burtt Davy) Burkill
- Dioscorea sylvatica subs. lydenbergensis Blunden, Hardman & F.J.Hind
- Testudinaria sylvatica var. lydenbergensis (Blunden, Hardman & F.J.Hind) G.D.Rowley
- Dioscorea sylvatica var. multiflora (Marloth) Burkill
- Dioscorea marlothii R.Knuth
- Testudinaria multiflora Marloth
- Testudinaria sylvatica var. multiflora (Marloth) G.D.Rowley
- Dioscorea sylvatica var. paniculata (Dummer) Burkill
- Dioscorea montana var. duemmeri R.Knuth
- Testudinaria paniculata Dummer
- Testudinaria sylvatica var. paniculata (Dummer) G.D.Rowley
- Dioscorea sylvatica var. rehmannii (Baker) Burkill
- Dioscorea rehmannii Baker
- Testudinaria rehmannii (Baker) G.D.Rowley
- Testudinaria sylvatica var. rehmannii (Baker) G.D.Rowley
- Tamus sylvestris Kunth
- Testudinaria glaucescens Hügel
ENGLISH: Elephant's Foot, Elephant's Foot Yam, Wild Yam
ZULU (isiZulu): Ingwevu, Ufudu - intelezi, Ugebeleweni
Description: The Elephant's Foot Yam, Dioscorea sylvatica, is a semi-tropical slender twining herb with annual stems growing from a massive, reticulated tuberous rootstock or caudex. The caudex that lie flat on the surface of the soil is divided into regular polygonal plates that become protuberant with age, divided by deep furrows. Vigorous, annual climbing stems can grow to as much as 4 or 5 metres in a season. Male and female flowers are borne on separate plants. Larger caudices rank as curiosities of the plant kingdom, and are eagerly sought after and admired by collectors of succulent plants.
Taxonomical notes: Dioscorea sylvatica is widespread and very variable and there are taxonomic problems with the different varieties. Now all the variants are assessed together as a single taxon, as the current poor delimitations of even such basic information as the distribution ranges of the different variants are making separate assessments extremely difficult.
Caudex (tuberous rootstock): The plants survive the dry season by means of a large underground tuber that develops very slowly and a seedling will eventually (in centuries?) become the size of an Elephant's foot (40-100 centimetres in diameter with an average tuber weight between 9 and 30 kg). If Dioscorea sylvatica is lucky enough to begin its life in rich soil, its caudex will remain mostly underground. In rocky and hilly situations, though, it will poke its caudex above ground. The caudex is quiet flat, wider than tall, irregularly shaped with "balconies" and forms a knobby, somewhat fissured, surface that somewhat resembles a multilobed pancake. The thick, woody outer layer of the caudex that aids in moisture retention and protection against predation also gives the plant great visual appeal.
Annual growth (vines): Vigorous, climbing, left-twining, growing to as much as 4 or 5 metres in a season.
Leaves: Alternate, deltoid, deeply cordate, shallowly 3-lobed, 5-8 cm long and broad, often almost appearing 2-lobed at the base, tapering to a long point at the apex; apical mucro 3-4 mm long.
Inflorescence: Flowers in lax, pendulous racemes up to 12 cm long, creamy white to very light green.
Male: Simple, shortly peduncled, 5-7.5 cm long. Pedicels 3-4 mm long, erecto-patent or patent with a small deltoid bract at the base and usually a bracteole at the middle. Expanded flower 4 mm in diameter. Segments oblanceolate, obtuse. Stamens much shorter than the perianth-segments.
Female: Female flowers in lax simple racemes, pedicels shorter than those of the male flowers, ovary linear-oblong, 6-8 mm long.
Flowering time (in habitat): November to February.
Fruit (capsule): Obovate, 4-winged, less than 2.8 cm long and 2 cm across.
Bibliography: Major references and further lectures
1) Umberto Quattrocchi “CRC World Dictionary of Medicinal and Poisonous Plants: Common Names, Scientific Names, Eponyms, Synonyms, and Etymology” (5 Volume Set) CRC Press, 03/May/2012
2) Cheryll Williams “Medicinal Plants in Australia: An Antipodean Apothecary” Volume 4 Rosenberg Publishing, 01/May/2013
3) Amitava Dasgupta, Catherine A. Hammett-Stabler “Herbal Supplements: Efficacy, Toxicity, Interactions with Western Drugs, and Effects on Clinical Laboratory Tests“ John Wiley & Sons, 21/Mar/2011
4) Janet M. Gibson “Wild flowers of Natal (coastal region)” Trustees of the Natal Publishing Trust Fund, 1975
5) J. G. Baker “Flora Capensis” page 246 1897
6) Fabian, A. & Germishuizen, G.“Wild Flowers of Northern South Africa.” Fernwood Press, Vlaeburg. Pages 82 - 83. (Includes a picture). 1997
7) Pooley, E. “A Field Guide to the Wild Flowers of KwaZulu-Natal and the Eastern Region.” Natal Flora Publications Trust. Durban. Pages 514 - 515. (Includes a picture). 1998
8) Wilkin, P. “Dioscoreaceae” FZ 12(2) Pages 136 - 137. (Includes a picture). 2009
9) Hyde, M.A., Wursten, B.T., Ballings, P. & Coates Palgrave, M. (2014). "Flora of Zimbabwe: Species information: Dioscorea sylvatica." http://www.zimbabweflora.co.zw/speciesdata/species.php?species_id=115460, retrieved 17 August 2014
10) Williams, V.L., Raimondo, D., Crouch, N.R., Cunningham, A.B., Scott-Shaw, C.R., Lötter, M. & Ngwenya, A.M. 2008. Dioscorea sylvatica Eckl. National Assessment: Red List of South African Plants version 2014.1. Accessed on 2014/08/17
11) Archibald, E.E.A. 1967. The genus Dioscorea in the Cape Province west of East London. Journal of South African Botany 33:1-46.
12) Blunden, G., Hardman, R. and Hind, F.J. 1971. "The comparative morphology and anatomy of Dioscorea sylvatica Eckl. from Natal and the Transvaal." Botanical Journal of the Linnean Society 64:431-446.
13) Burkill, I.H. 1952. "Testudinaria as a section of the genus Dioscorea." Journal of South African Botany 18:177-191.
14) Codd, L.E. 1960. "Drugs from wild yams." African Wildlife 14(3):215-234.
15) Cunningham, A.B. 1988. "An investigation of the herbal medicine trade in Natal/KwaZulu." Investigational Report No. 29. Institute of Natural Resources, Pietermaritzburg.
16) Cunningham, A.B. 1993. "African medicinal plants: setting priorities at the interface between conservation and primary health care." People and Plants working paper 1. UNESCO, Paris.
17) Dold, A.P. and Cocks, M.L. 2002. "The trade in medicinal plants in the Eastern Cape Province, South Africa." South African Journal of Science 98:589-597.
18) Germishuizen, G., Meyer, N.L., Steenkamp, Y. and Keith, M. (eds). 2006. "A checklist of South African plants." Southern African Botanical Diversity Network Report 41 SABONET, Pretoria.
19) Mander, M. 1998. "Marketing of indigenous medicinal plants in South Africa: a case study in KwaZulu-Natal." Food and Agriculture Organization of the United Nations, Rome.
20) Raimondo, D., von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. and Manyama, P.A. 2009. "Red List of South African Plants." Strelitzia 25. South African National Biodiversity Institute, Pretoria.
21) Rowley, G.D. 1987. "But are they any use?" In: "Caudiciform & pachycaul succulents" (pp. 221-224), Strawberry Press, Mill Valley, California.
22) Rowley, G.D. 2001. "Dioscorea" In: U. Eggli (ed), "Illustrated handbook of succulent plants: Monocotyledons" (pp. 254-257), Springer, Berlin.
23) Scott-Shaw, C.R. 1999. "Rare and threatened plants of KwaZulu-Natal and neighbouring regions." KwaZulu-Natal Nature Conservation Service, Pietermaritzburg.
24) Von Ahlefeldt, D., Crouch, N.R., Nichols, G., Symmonds, R., McKean, S., Sibiya, H. and Cele, M.P. 2003. "Medicinal plants traded on South Africa's eastern seabord." Porcupine Press, Durban.
25) Wilkin, P. 2001. "Dioscoreaceae of south-central Africa." Kew Bulletin 56(2):361-404.
26) Williams, V.L. 2007. "The design of a risk assessment model to determine the impact of the herbal medicine trade on the Witwatersrand on resources of indigenous plant species." Unpublished PhD Thesis, University of the Witwatersrand, Johannesburg.
27) Williams, V.L., Witkowski, T.F. and Balkwill, K. 2007. "Volume and financial value of species traded in the medicinal plant markets of Gauteng, South Africa." International Journal of Sustainable Development & World Ecology 14(6):584-603.
28) Fred Dortort “I Yam What I Yam-Dioscorea” in: Botanical garden newsletter University of California Volume 28, Number 1 Berkeley Winter 2003
Young specimen. Photo by: K.k. Agrawal
Dioscorea sylvatica Female. Photo by: © Plantemania
Cultivation and Propagation: Dioscorea sylvatica responds well to cultivation and makes an easy and wonderfully unusual houseplant. Plants even five to ten years old are extremely nice. Vigorous, annual climbing stems can grow to as much as 4 or 5 metres in a season, however these can be trained quite comfortably around a wire hoop set in a pot when grown indoors.
Exposure: It prefers light shade, but keep the caudex in the shade.
Waterings: It needs moderate to regular water. Slow down or withheld water when the tuber is dormant in summer (after shedding its leaves). It will start growing again in Autumn. Watering can recommence once the plant has shown signs of producing a fresh shoot. Sometimes it ignores its proper growing seasons (from autumn to spring ) and keeps its vines growing long into its rest period, or sends up new vines much earlier than expected. In that case, paying attention to the plant and not the calendar is a good idea.
Hardiness: It is easy to grow if a winter temperature of 5° C can be maintained.
Medical uses: Poisonous. Antibacterial, for wounds, sores, mastitis, abscesses. Dioscorea sylvatica contains diosgenin, a substance that was used to manufacture cortisone and other steroid hormones. It also shows antibacterial activity: extracts of D. sylvatica (tuber bark) have shown antibacterial activity against Escherichia coli. D. sylvatica may produce mild inflammation and itching when rubbed on the skin, with cutaneous reactions caused in part by raphides of calcium oxalate.
Propagation: Seeds, difficult from cuttings. Sow seeds 5mm deep and keep them warm. Sprouts best in indirect light. The seedlings' caudex forms below ground and will grow much faster if left underground for a couple of years.
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