Tree is usually up to 12m high. Trunk with small protruding bulges. The simple Leaves lack stipules. The small bisexual Flowers have 3 sepals and 10 petals. Fruit is a berry with shiny Seeds.
Warburgia salutaris, Warburgia ugandensis, Warburgia breyeri, Chibaca salutarus.
RSA No. 488.
Common names: Pepper-bark tree, pepper-leaf, pepper-root, peperbasboom, East African greenheart, Fever tree.
Family: Canellaceae: Family of flowering plants. They are usually evergreen trees or shrubs with aromatic bark. Leaves are simple, entire, alternate and have a peppery taste. The small, regular, bisexual Flowers usually have 3 coriaceous imbricate (having regularly arranged, overlapping edges, as roof tiles or fish scales) Sepals. There are 10 free Petals in 2 whorls. The outer whorl petals are larger and thicker. The Anthers are monodelphous (having the stamens at least partly united into one group by their filaments) around the superior Ovary. At least 2-5 Stigmas are present. The Fruit is a berry (pulpy, indehiscent fruit like a grape or tomato). The 2 to many Seeds are shiny with a fleshy, oily endosperm (the starch and oil-containing tissue of many seeds; often referred to as the albumen).
Name derivation: Warburgia was named after Dr Otto Warburg, 1859-1938. He was born in Hamburg and was a German-Jewish botanist. He was also a notable industrial agriculture expert. He was later the founder of institute of natural history in Jerusalem. salutaris in Latin means healthful – possibly referring to the use in herbal medicine.
Conservation Status: EN (Endangered). 2009 (Raimondo et al.). It is endangered partly because of over exploitation for herbal medicine. In southern Africa Warburgia salutaris is the only species.
Tree is erect and usually up to 12m high. It may be much higher in Kenya. The young branches are smooth and grey with conspicuous, unusual yellow/orange Lenticels (usually raised corky oval or elongated area on the plant that allows the interchange of gases with the environment). The Bark is aromatic and peppery. The Trunk is dark brown with a great number of small protruding light brown/red bulges giving the “pepper” effect and making the trunk roughish. The tree is glabrous (hairless).
The simple (have a single blade which may have incisions that are not deep enough to divide the blade into leaflets), spirally arranged Leaves are coriaceous (leathery), alternate and elliptic to lanceolate or oblanceolate. This is an aromatic evergreen tree. The Margin is entire (with a continuous margin, not in any way indented but may be hairy), rolled under and may be wavy. Leaves are hairless and measure up to 11 x 3cm. Apex and Base are narrowly tapering – the base more so. Gland dots are present and may be visible when the leaf is held against a strong light. The Midrib is slightly off-centre. It is visible above and protrudes below. The upper leaf surface is darker. Leaves have a short Petiole (leaf stalk) – up to 5mm long and Stipules (basal appendages of the petiole) are absent.
Flowers are borne singly or in Cymes (broad, more or less flat-topped inflorescence with the central flower opening first), on short robust stalks in leaf axils. They are small – 6/7mm wide, green or whitish, bisexual, actinomorphic (regular, symmetrical). Each flower has 3 imbricate (having regularly arranged, overlapping edges, as roof tiles) and persistent fleshy Sepals. There are 10 obovate, gland-dotted Petals in 2 rows of 5. The outer 5 are thicker, larger, and less yellow than the inner 5. There are 10 Stamens whose Filaments are united in a tube which encloses the ovary and part of the style. They are more or less the same length as the petals and are attached to the Receptacle (is that expanded tip of the flower stalk from which the floral parts develop) below the ovary. The sessile Anthers have fleshy apical appendages on the upper part of the tube. They have longitudinal extrorse (outwards) dehiscence. There is a single Pistil (a unit of the Gynoecium, the female element of the flower, composed of the Ovary, Style and Stigma) with a superior one locular Ovary. Above this is a single, thick Style appearing as if cut off at the end and is almost enclosed in the staminal tube. It has 5 stigmatic patches around the sides. Before examining with a hand lens the perianth should be removed. (Feb-Apr).
The nearly cylindrical or oval Fruit is a Berry, (pulpy, indehiscent fruit like a grape or tomato) which up to 5cm wide and covered with glands. The pericarp (fruit wall) of the berry is coriaceous (leathery). It is initially green, maturing into a rough leathery purple colour with a white bloom. The Ovary is enveloped by a green bracteole. It contains many reniform (kidney-shaped) Seeds. These shiny seeds have an oily, fleshy endosperm (the starch and oil-containing tissue of many seeds; often referred to as the albumen). (Oct-Jan).
Distribution & Ecology
These Trees are found in dry rocky hillsides and wet forests. They are located in KwaZulu-Natal e.g. in coastal forests, Gauteng, Limpopo e.g. along the Blouberg and Soutpansberg mountains, Mpumalanga e.g. along the Drakensberg escarpment, Swaziland, Malawi, Zambia, Zimbabwe e.g. in the Eastern Highlands, and into tropical Africa. The tree is drought resistant and has the ability to coppice (young tree stems that are repeatedly cut/burned down to near ground level. This may cause regrowth from the stump or roots) and grows best in frost-free areas.
The Wood may be used as timber but is not very durable and tends to split when nailed. Heartwood is initially yellow to greenish, eventually turning dark. The wood is oily and is not resistant to insect attack. The tree also possesses aromatic Oils. The glossy green Leaves are aromatic when crushed. They have a burning taste due to the presence of chemicals produced by plants as a protection against herbivores and against infection by microorganisms. The tree is becoming rare but now steps are being taken to save it. The Warburgia project is officially sponsored by Sappi to save this tree. It involves growing of many trees in the KNP and passing some on to local communities. Fortunately, the tree is a fast grower. The intent is to persuade healers to use the leaves rather than bark. Dogs can be trained to find the plants. The plant can be Grown from seeds and from cuttings. Seeds can be stored for a short time at 3 degrees Celsius (Centigrade). It makes a good shade tree.
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.
Schmidt, S. Lotter, M. & McCleland, W. 2002. Trees and Shrubs of Mpumalanga and the Kruger National Park.
Article by Petro Kotze in SANParks Times September 2015.