Warburgia salutaris

General Information

This glabrous, evergreen Tree with aromatic, peppery bark is up to 12m high and has lenticel bulges.  Bark becomes rough and peppery.  Simple Leaves have entire margins and lack stipules.  Small bisexual Flowers have 3 sepals and 10 petals.  Anthers extend from a staminal tube, and the single pistil has a superior ovary & ends in a truncate stigma.  The roundish Fruit is a berry with shiny kidney-shaped seeds.

Detailed Description

Previous Names: Warburgia breyeri, Chibaca salutaris.

SA No. 488.

Common names: (Afr) Koorsboom, Peperbasboom, Peperblaarboom, Sterkbos.  (Eng) Fever Tree, Pepper-bark, Pepper-bark Tree, Pepper-leaf, Pepper-root.  (isiZulu) Amazwecehlabayo, Isibaha, Isibhaha.  (Setswana) Molaka,  Shibaha.  (Tshivenda) Manakha, Mulanga.

Family Canellaceae.  Worldwide this small family has 6 genera and 16 species.  (In South Africa there is one genus and one species).  Plants in this family are usually small to medium, evergreen trees (rarely shrubs) that are smooth, hairless and with aromatic bark.   Conspicuous unusual lenticels are present.  The simple, entire, petiolate and pinnately veined Leaves may be alternate, spiral or distichous (leaves arranged in two vertical rows on opposite sides of the stem) in arrangement.  Leaves lack stipules (basal appendage of the petiole – the leaf stalk) and have a peppery taste.  Inflorescences are terminal or axillary and may be simple.  The small regular bisexual Flowers usually have 3 persistent almost circular and imbricate (having regularly arranged, overlapping edges) Sepals.  Petals are obovate (egg-shaped – with the narrower end at the base) and in 2 whorls of 5 each.  The outer whorl has slightly thick concave petals and the Inner thin whorl develop yellow spatula shaped petals.  The Fruit is a berry (pulpy, indehiscent fruit like a grape or tomato) with a persistent calyx.  The leathery fruit wall is wrinkled.  The 2 to many flatty Seeds are shiny above and less so below.  Seeds have a fleshy, oily endosperm (the starch and oil-containing tissue of many seeds; often referred to as the albumen).  Warburgia salutaris is the only indigenous species in South Africa.

Name derivation: Warburgia: 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.  Later on in life he became the founder of institute of natural history in Jerusalem.  salutaris in Latin means healthful – possibly referring to the use in herbal medicine.  Warburgia is a genus of 4 species – confined to Africa (1 in SA).

Conservation: National Status: EN (Endangered).  Assessed Raimondo et al. (2009).  It is endangered partly because of over exploitation for its stem and root bark for herbal medicine.  The risk has now been increased from Vulnerable to Endangered.  But hopefully the steps that have now been taken will have a lasting effect of the tree sustainability.

Tree

This erect glabrous (hairless) Tree is usually up to 12m high in South Africa.  It is often much higher in Kenya.  Pith (usually the soft spongy central area of the stem) is homogeneous (of a uniform structure). The young branches are smooth and brown with conspicuous, unusual yellow/orange Lenticels (usually raised corky oval or elongated area on the plant that allow the uncontrolled interchange of gases with the environment – photo 99).  These orange lenticels help with identification.  The Bark becomes rough, aromatic, peppery and pungent tasting.  The inner bark is reddish.

Leaves

This is an aromatic evergreen tree.  The upper leaf surface is a darker green.  Alternately or spirally

This is an aromatic evergreen tree.  The upper leaf surface is a darker green.  Alternately or spirally arranged (photo 428), hairless Leaves are coriaceous (leathery) and simple (have a single blade that may have incisions that are not deep enough to divide the blade into leaflets).  Stipules (basal appendages of the petiole) are absent.  Leaves are up to 11 x 3cm (photo 117) and elliptic, lanceolate or oblanceolate (photo 117) and have a distinctive peppery smell when crushed.  The rolled under and wavy Margin is entire (with a continuous margin, not in any way indented (photo 117).  The Apex and Base are narrowly tapering – the base more so.  Gland dots are present and are visible as whitish dots (photo 381).  The Midrib (the main rib of a leaf or leaf-like part, a continuation of, but excludes the petiole is asymmetric (slightly off-centre).  It is visible above and protrudes, at least part way, below (photo 117).  The Leaf blade has pinnate venation that is characterized by a single main vein (the midrib), with smaller veins branching off from it in a feather-like arrangement.  Unless viewed against a strong light (photo 381) the smaller veins are indistinct.   In this photo the veins meet prior to reaching the margin.  Leaves have a short Petiole (leaf stalk) that is up to 5mm long and is not part of the midrib.

Flowers

The small (up to 6-7mm in diameter) inconspicuous yellowish or green Flowers (photo 38) are borne singly or in Cymes (broad, more or less flat-topped inflorescence with the central flower opening first).  Each flower rests on a short robust Pedicels (stalk of a single flower) in leaf axils (photo 38).  In this photo, young dark lenticels are visible.  Flowers are bisexual and actinomorphic (Regular, symmetrical.  Flowers are vertically divisible into similar halves by more than 1 plane passing through the axis).  Each flower has 3 persistent fleshy, coriaceous (leathery) Sepals that are imbricate (having regularly arranged, overlapping edges, like roof tiles) – photo 38 – top left.  Mature sepals are free.  There are 10 obovate (egg-shaped – with the narrower end at the base), gland-dotted and overlapping 10 Petals in 2 rows of 5.  The outer petal whorl is larger and thicker with almost clear gland dots.  The inner whorl of 5 petals is thinner textured and spathulate (the end is broad, and base is narrow).

In the Androecium (the male element of the flower) the Stamens (male reproductive part of a flower) have up to 20 Filaments (the usually long slender stalks that supports each anther) that are united forming a clear staminal tube (photo 838) that is slightly shorter than petals.  This tube encloses the ovary and most of the style.  Stamens are attached below the superior ovary to the Receptacle (is that expanded tip of the flower stalk from which the floral parts develop).  The exerted Anthers (where the pollen grains are formed) are sessile on the upper part of the staminal tube and distinctly joined at the base.  Mature anthers have outwardly dehiscence (is the splitting, at maturity, along a built-in line of weakness in a plant structure in order to release its contents, and is common among fruits, anthers and sporangia.  The Gynoecium is the female reproductive portion of a flower.  In this plant it contains a single Pistil (composed of the Ovary, Style and Stigma).  This plant has a superior one locular Ovary (with 1 ovule and 2-many ovules).  Above this is a single thick short Style that is truncate (appearing as if cut off at the end – photo 38 – upper LHS).  The style usually ends with a single 2-6 lobed stigma.  It is almost enclosed within the staminal tube and has 5 stigmatic patches around the sides.  The Perianth (a collective term for the calyx and corolla) should be removed before examining the male and female parts with a hand lens (photo 838).  (Jan-Apr).

Fruit

The nearly spherical Fruit is a Berry, (pulpy, indehiscent fruit like a grape or tomato) with a persistent calyx which is up to 4cm wide and covered with glands.  The pericarp (ripened fruit wall) of the berry is coriaceous (leathery – photo 249).  The fruit is initially green (photo 239), maturing into a distinctive rough leathery purple colour with a white bloom (photo 249).  It contains the reniform (kidney-shaped) Seeds (photo 242).  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

This is a tropical species, and trees are located in evergreen forests, dry rocky hillsides and further north in wet forests.  They occur in KwaZulu-Natal e.g. in coastal forests, Limpopo e.g. along the Blouberg (blue mountains) Soutpansberg mountains, and Mpumalanga e.g. along the Drakensberg escarpment.  Beyond South Africa they occur in Eswatini (Swaziland), Malawi, Zambia, Zimbabwe e.g. in the Eastern Highlands where it is now probably extinct.  It also grows in southern Mozambique and into tropical Africa.  Leaves are browsed by antelope, hippo, black rhino.  To the north of South Africa, the remaining 3 species occur.  The tree is drought resistant and has Coppice growth (In this case, when stems are cut or burned, it causes regrowth from the stump or roots).  The smell and taste of the leaves makes this plant easier to identify.

Ethnobotany

The Wood may be used as timber but is not very durable and tends to split when nailed.  Heartwood is initially yellow to greenish and eventually darkens on exposure to air.  The wood is oily and is not resistant to insect attack.  The tree also possesses aromatic Oils and 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 inner bark is reddish and bitter.  Local herbalists use the peppery Bark to treat at least 12 ailments including coughs, colds and malaria.  It has also been used against witchcraft.  The distinctive peppery aroma of its Leaves has resulted in its use as a condiment for food dishes and beverages. The dried Wood is used for firewood.  Collectively this is why the problem is so great.  The extent of debarking is substantial as is the bark is illegally sold in local markets.  This tree is becoming endangered, but steps are now being taken to save it.  In order to achieve this, SAPPI officially sponsored the Warburgia Project.  This involves growing of many trees in the relative safety of Kruger National Park and passing some on to local communities – including Eswatini (Swaziland).  Sappi has also provided funding for uniforms and bicycles to assist the rangers who safeguard the trees in the Kruger National Park.  Trained dogs can help in the location of these plants.  Fortunately, the tree is a fast grower.  The intent is also to persuade healers to use the leaves rather than bark.  The plant can be Grown from seeds but does best from spring cuttings.  Seeds can be stored for a short time at 3 degrees Celsius (Centigrade).  This plant makes a good shade tree and grows best in frost-free areas.  Young plants especially need to be protected from frost.

References

Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of Southern Africa, edn 3. Struik, Cape Town.

Burrows, J.E., Burrows, S.M., Lotter, M.C. & Schmidt, E. 2018. Trees and Shrubs Mozambique.  Publishing Print Matters (Pty) Ltd.  Noordhoek, Cape Town.

Harvey-Brown, Y., Mhlongo, N.N., Raimondo, D., Williams, V.L., Botha, J., Hofmeyr, M. & Swemmer, L. 2022. Warburgia salutaris (G.Bertol.) Chiov. National Assessment: Red List of South African Plants version . Accessed on 2025/03/25.

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. Jacana, Johannesburg.

Sappi sponsored Warburgia project.

https://en.wikipedia.org/wiki/Warburgia_salutaris

http://www.farmersweekly.co.za/article.aspx?id=62795&h=How-humus-can-save-the-world

http://www.plantzafrica.com/plantwxyz/warburg.htm

http://www.zimbabweflora.co.zw/speciesdata/species.php?species_id=140560

http://www.iucnredlist.org/details/30364/0

http://www.botanicalsociety.org.za/ProjectsAndActivities/Useful%20Plants/11%20The%20Pepper-bark%20Tree%20March%202010.pdf

http://www.worldagroforestry.org/treedb2/speciesprofile.php?Spid=1731

http://posa.sanbi.org/flora/browse.php?src=SP

https://en.wikipedia.org/wiki/Canellaceae

https://en.wikipedia.org/wiki/Otto_Warburg_(botanist)

http://www.worldfloraonline.org/taxon/wfo-7000000108. Accessed on: 29 Mar 2025′