This tree is a priority species for conservation and cultivation in gardens, as it is over-harvested in the wild for medicinal use and is a very popular item for sale at street markets.

Description
This is an evergreen, slender tree that grows from 5 to 10 m tall. The dark green, glossy leaves are paler green below with entire margins, and are simple, alternately arranged, elliptic to lanceolate. The midrib is slightly off-centre with the tapering apex and base. The leaves have a bitter, burning, aromatic taste.

It has white to greenish flowers of up to 7 mm in diameter. The flowers are solitary, axillary, or in tight, few-flowered heads, borne on short, robust stalks in the axils of the leaves. These flowers develop into round, oval berries, narrowed towards the base, are dark green, turning purple when ripe, leathery in texture and covered with glands. The stem is covered by a rich brown bark that is also bitter and peppery.

Distribution
This is a tropical forest tree which extends southwards as far as KwaZulu-Natal, eastern and northern Gauteng and across Swaziland. It also occurs in Malawi. Its growth habitat is forests and kloofs.

Name derivation and historical aspects
The genus Warburgia was named after Dr Otto Warburg, 1859-1938, who was born in Hamburg. He lectured in botany at the University in Berlin,Germany and was also the author of numerous botanical papers. The specific epithet salutaris in Latin means healthful. The English common name pepper-bark is from the inner bark that is pungent. Isibaha is an old name in the history of Africa, and is thought to be based on an Arabian word which dates back to the days when the Arabs traded with Africa.

Cultural aspects
Medicinally, the pepper-like, bitter stems and root bark are used to cure many ailments. As an expectorant or smoked, they are a widely used remedy for common colds. Dried and ground, they make a snuff used to clear the sinuses. Taken orally are believed to cure spots in the lungs. Both stems and root bark are a remedy for malaria. Powdered and mixed with water, they are believed to cure sores in the mouth. The wood is not well known for timber in South Africa probably because of its rarity. According to Palmer& Pitman (1973), in Kenya the leaves of the pepper-bark are sometimes added to curries and the wood is sometimes used in building.

Growing Warburgia salutaris

Warburgia salutaris is cultivated from seed and vegetatively from cuttings. The best time to take cuttings is in spring. The tree grows in well-drained soil, with good aeration. Soil should be rich in organic matter in the form of well-rotted compost. The pepper-bark is a nice evergreen tree for both small gardens and big estates. It is also a suitable plant for a hedge as it responds well to pruning. This tree is sensitive to frost and should be protected when young.

References and further reading

• Coates Palgrave, K. 1977. Trees of southern Africa, edn 2. Struik, Cape Town.
• Palmer, E. & Pitman, N. 1973. Trees of southern Africa, vol. 3. Balkema, CapeTown.
• Van Wyk, B-E. & Gericke, N. 2000. People's plants. Briza Publications, Pretoria.

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  Author Giles Mbambezeli Kirstenbosch NBG August 2004