Tree may reach 7m high and has very poisonous latex. Simple, entire Leaves are thick and leathery. White Flowers are bisexual, regular and 5-merous. Fruit is a fleshy berry with up to 2 flat, oval Seeds.
Acokanthera oblongifolia, Acokanthera spectabilis, Carissa spectabilis
RSA Tree No. 638.
Common names: Dune Poison Bush, Poison Bush, Duinegifboom, Hottentots’s poison, Kaffergifboom, Poison arrow bush.
Family: Apocynaceae (Oleander or impala lily (Adenium multiflorum) family). This family includes the exotic genera Oleander and Plumeria (Frangipani). Indigenous genera containing trees include Acokanthera, Adenium, Carissa, Rauvolfia and Tabernaemontana. Currently the family has 366 genera and in excess of 5 000 species. In RSA, there are 90 genera and about 700 species. All have milky or clear sap. The simple, entire and pinnately veined Leaves are usually opposite and may have stipules situated between the petiole and the stem. Inflorescence is usually a cyme (a broad, more or less flat-topped, determinate flower cluster, with central flowers opening first). The regular and bisexual Flowers are usually bracteate. The Calyx has 4-5, usually free sepals and the 4-5 Petals are joined – at least at the base of the staminal column. A corona (an extension) is often present either on the corolla, or on arising from the base of the staminal column. The 4-5 Stamens are variously located and have anthers with 2 pollen sacs. The superior to half-inferior Ovary has 2 carpels. Fruit is various. The often-compressed Seeds may have a tuft of silky hair at the micropylar (a small opening in the surface of an ovule, through which the pollen tube penetrates, often visible as a small pore in the ripe seed. During germination, the seedling’s radicle – embryonic root – emerges through the micropyle) end.
Name derivation: Acokanthera –Greek: “Apo” away and “kyon” dog possibly because of being poisonous to dogs. Oblongifolia – referring to the oblong leaves.
Conservation Status: L C (Least Concern).
This unarmed plant may be a shrub or a small Tree up to 7+m high. The trunk may reach 23cm wide. Branches are erect with dark grey, rough bark. They may be ribbed. Young branches are green (photo 358). Very poisonous milky latex is present. The plant is evergreen or semi-deciduous.
The simple (have a single blade which may have incisions that are not deep enough to divide the leaf into leaflets) entire (with a continuous margin, not in any way indented) Leaves may be lanceolate, oblong or elliptic but not round. They are up to 12 x 6 cm. Leaves lack hairs and are thick and leathery. They are in nearly opposite pairs – less so than in Acokanthera oppositifolia. The Apex is rounded and may have a hair-like tip. Margins are rolled inwards. Leaves are shiny above and slighter lighter below. The Base is broadly tapering to rounded. There is a distinctive Midrib which protrudes below. Side Veins loop before reaching the margin. The thick, yellowish Petiole is wrinkled, grooved above and may reach 1cm long. Stipules (basal appendage of the petiole) are absent.
The light green Buds are long and slender. The white, sweetly scented Flowers may be slightly pink. They are located in Cymes (broad, more or less flat-topped, determinate flower cluster, with central flowers opening first) in leaf axils of young shoots. Flowers are bisexual, regular and 5-merous. The short Sepals are free and ovate to lanceolate. The thin, tubular corolla tube is up to 2cm long and may be red-coloured ending in a hairy opening. The 5 white Lobes are up to 7mm long and may be slightly turned inwards. They may be tinged with pink. The 5 epipetalous Stamens are inserted near the top of the Corolla tube and alternate with corolla lobes. Anthers are mucronate (having an abruptly projecting point) and do not appear above the opening of the corolla tube. They dehisce longitudinally. The superior Ovary extends into a slender style ends with a short stigma that is minutely bifid. (Aug-Nov+).
The initially green, almost spherical, fleshy Fruit is a berry (pulpy, indehiscent fruit like a grape or tomato) that matures to a plumb red and finally shrivels to a purplish black. Maximum size is 2,5-2,2cm. A persistent calyx is present. One or 2 flat oval seeds are produced. Each berry is hairless and up to 1,5cm long.
Distribution & Ecology
These Trees are found in the Eastern Cape, Kwazulu-Natal, Limpopo, Northwest, Swaziland, Zimbabwe, Mozambique and northwards. In the shade, the plants are straggly. They often occur not far from the sea in dry forests and coastal thickets. These drought resistant hardy plants growing well in semi-shade up to an altitude of 2 300m. They may appear together with Erythrina caffra.
All parts of this plant are poisonous – especially young fruits. Arrow poison has been made from it. It is thus not suitable for gardens. Be careful collecting unknown firewood. The milky sap is very poisonous and contains cardiac glycosides. Even when handling this specimen latex gloves should be used. It is used in local medicine – caution!
Boon, R. 2010. Pooley’s Trees of eastern South Africa. Flora and Fauna Publications Trust, Durban.
Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.
Lawrence, G. H. M, 1951. Taxonomy of Vascular Plants, The Macmillan Company, New York. Tenth Printing 1965.
Palmer, E. & Pitman, N. 1972. Trees of southern Africa, Balkema, Amsterdam, Cape Town.
van Wyk, B. & van Wyk, P. 1997 Field guide to Trees of Southern Africa, Struik, Cape Town.