Adenium boehmianum (PROTA)

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Adenium boehmianum Schinz


Protologue: Verh. Bot. Vereins Prov. Brandenburg 30: 259 (1888).
Family: Apocynaceae
Chromosome number: 2 n = 22

Synonyms

  • Adenium obesum (Forssk.) Roem. & Schult. subsp. boehmianum (Schinz) G.D.Rowley (1983).

Vernacular names

  • Bushman poison (En).
  • Unguiu (Po).

Origin and geographic distribution

Adenium boehmianum occurs naturally in Angola and Namibia.

Uses

The extremely bitter root sap and latex are boiled to prepare arrow poison in Namibia and neighbouring parts of Angola. The arrow poison is used for hunting large game such as zebra and wildebeest. Plants are occasionally grown as ornamentals.

Production and international trade

There is some international trade in seeds and plants of Adenium boehmianum for ornamental purposes.

Properties

The arrow poison prepared from Adenium boehmianum has strong cardiotoxic effects. When an animal is hit it usually dies within a few hours and within a few hundred metres from where it was shot. The poisonous compounds in the root and stem latex have been identified as cardiac glycosides. The most important ones are: echujine (composed of the aglycone digitoxigenin, the sugars D-cymarose and 2 molecules of D-glucose), digitalinum verum (composed of gitoxigenin, D-digitalose and D-glucose), somaline (composed of digitoxigenin and D-cymarose) and abobioside (composed of abogenin and D-cymarose).

Description

Succulent shrub up to 2.5(–3.5) m tall, with rootstock and white latex in all parts; stem swollen at base, up to 40(–60) cm in diameter; branches erect, sparingly hairy when young becoming scabrid, greyish white. Leaves arranged spirally, clustered at the end of branches, simple; stipules minute or absent; petiole 1–3(–7) mm long; blade obovate, 8–15 cm × 4.5–8 cm, often folded upwards along the midrib, base cuneate, apex usually emarginate, entire, glaucous or pale green, leathery, hairy at least when young, pinnately veined with distinct lateral veins. Inflorescence a dense terminal cyme; bracts narrowly oblong to narrowly ovate, 5–11 mm × 1–3 mm, acuminate, pubescent. Flowers bisexual, regular, 5-merous, showy, appearing before or with the leaves; pedicel 5–10 mm long; sepals lanceolate, 6–12 mm long, fused at base, acuminate, densely hairy; corolla with tube 0.7–1 cm long and obovate lobes, spreading, 2. 5–3.5(–4.5) cm × 1–1.5 cm, slightly undulate, pink to mauve, darker in the throat, hairy outside; stamens inserted near base of corolla tube, included, anthers forming a cone covering the pistil, base sagittate, 5–7 mm long, with long apical appendices; ovary superior, composed of 2 free carpels, glabrous, styles fused, slender with well-developed clavuncula. Fruit consisting of 2 linear-oblong follicles, coherent at base, 10–18 cm long, tapering at both ends, spreading or recurved when mature, opening by a longitudinal slit, many-seeded. Seeds linear-oblong, 7–9 mm long, brown, striate, with tufts of long dirty white to pale brown hairs at both ends.

Other botanical information

Adenium comprises 5 species, which are sometimes merged into a single one, Adenium obesum (Forssk.) Roem. & Schult. with 6 subspecies.

Adenium swazicum

Adenium swazicum Stapf may resemble Adenium boehmianum, but differs in its narrower leaves. It has a limited distribution in Swaziland and neighbouring parts of South Africa and southern Mozambique and is planted as an ornamental. Some selections are ‘Boyce Thompson’ with deep purplish pink flowers, and ‘Perpetual Pink’, which is robust, upright and with large pink flowers.

Growth and development

Plants bear leaves for about 3 months only. This period cannot be extended by cultural practices in cultivation. They flower for a few weeks only.

Ecology

In its natural range Adenium boehmianum is widespread in granitic rocky localities and occasionally at edges of swamps. The largest plants are found along the escarpment of the Mary river in Kaokoland in Namibia.

Propagation and planting

As an ornamental Adenium boehmianum can probably be propagated like Adenium obesum, by seed, grafting or cuttings.

Management

Plants used for making arrow poison are always collected from the wild. As a container plant Adenium boehmianum is handled in the same way as other large succulents.

Genetic resources

Although the natural distribution of Adenium boehmianum is restricted, it seems not to be in danger of genetic erosion.

Prospects

More research into the chemical composition and pharmacological activities of the compounds of Adenium boehmianum seems warranted. Its prospects as an ornamental seem limited because of the short flowering period.

Major references

  • Codd, L.E., 1963. Apocynaceae. In: Dyer, R.A. & Codd, L.E. (Editors). Flora of southern Africa. Volume 26. Botanical Research Institute, Department of Agricultural Technical Services, Pretoria, South Africa. pp. 244–296.
  • Dimmitt, M.A. & Hanson, C., 1992. The genus Adenium in cultivation. Part 2: A. swazicum, A. boehmianum and A. oleifolium. Cactus and Succulent Journal 64(3): 110–111.
  • Neuwinger, H.D., 1996. African ethnobotany: poisons and drugs. Chapman & Hall, London, United Kingdom. 941 pp.
  • Plaizier, A.C., 1980. A revision of Adenium Roem. & Schult. and of Diplorhynchus Welw. ex Fic. and Hiern (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 80–12. Wageningen, Netherlands. 40 pp.
  • Rowley, G.D., 1983. The Adenium and Pachypodium handbook. Smart & Co. Ltd., Brackley, United Kingdom. 95 pp.
  • Stapf, O., 1902–1904. Apocynaceae. In: Thiselton-Dyer, W.T. (Editor). Flora of tropical Africa. Volume 4(1). Lovell Reeve & Co, London, United Kingdom. pp. 24–231.

Other references

  • von Koenen, E., 2001. Medicinal, poisonous and edible plants in Namibia. Klaus Hess Verlag, Göttingen, Germany. 336 pp.
  • van Wyk, B.E. & Gericke, N., 2000. People’s plants: a guide to useful plants of southern Africa. Briza Publications, Pretoria, South Africa. 351 pp.

Sources of illustration

  • Plaizier, A.C., 1980. A revision of Adenium Roem. & Schult. and of Diplorhynchus Welw. ex Fic. and Hiern (Apocynaceae). Mededelingen Landbouwhogeschool Wageningen 80–12. Wageningen, Netherlands. 40 pp.

Author(s)

  • L.P.A. Oyen, PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, Netherlands

Correct citation of this article

Oyen, L.P.A., 2006. Adenium boehmianum Schinz. In: Schmelzer, G.H. & Gurib-Fakim, A. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, Netherlands. Accessed 14 December 2017.