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Hagenia abyssinica (Bruce) J.F.Gmel.

Syst. nat. 2(1): 613 (1791).
Chromosome number
2n = unknown
Brayera anthelmintica Kunth (1824), Hagenia anthelmintica (Kunth) Eggeling (1940).
Vernacular names
Kosso, kousso, cusso (En). Kosso, kousso, cousso, cossoutier (Fr). Mturunga, mdobore (Sw). In Amharic (Ethiopia) the name ‘kosso’ can be used to indicate the tree, inflorescence, medicine, or parasite (tapeworm) treated with the plant.
Origin and geographic distribution
Hagenia abyssinica is indigenous to montane regions of eastern, central and southern Africa, mostly above 2000 m altitude. It is found in the Democratic Republic of Congo, Sudan and Ethiopia, and south to Malawi, Zambia and Zimbabwe.
Throughout history, Hagenia abyssinica has been used as an anthelmintic in Ethiopia and other parts of Africa. Almost every Ethiopian used to drink an extraction of dried flowers once every 1-3 months to expel tapeworm, which was, and to some extent still is, a common parasite in Ethiopia where raw meat, a source of infection, is a delicacy and a very popular item in the diet. Honey, obtained from beehives located near Hagenia abyssinica trees and collected immediately after their flowering, is also said to be effective in expelling tapeworms. In the 19th Century, kosso was widely used as an anthelmintic in Europe. It is also used, often in a mixture with parts of other plants, as a medicine to treat syphilis, scrofula, malaria, fever and cough. Hagenia abyssinica has strands of red flowers, giving the tree ornamental value. The wood has a handsome appearance and is suitable for furniture, cabinet work, floors, veneers, tools and fences. In Tanzania, Hagenia abyssinica is grown in agroforestry systems; the wood is used as fuel, the leaves as fodder and green manure, and the seeds as a condiment or spice. In the Kilimanjaro area, the bark is used for dyeing textiles yellowish red.
Production and international trade
Hagenia abyssinica has been used in Ethiopia for centuries. It became known to European medicine as a tapeworm remedy early in the 19th Century. Before 1950, kosso was listed as an anthelmintic in the pharmacopoeias of about 30 countries. With the advent of chemical anthelmintics with reliable dosage and action, the international use of kosso as tapeworm expellent disappeared. At present, kosso is still locally traded and used in Ethiopia where it is on sale in almost every traditional market. However, its use is rapidly diminishing. The average weight of samples of dried flowers sold in Ethiopia is about 24 g (considered enough for one treatment), samples usually varying between 10-50 g.
Kosso is an anthelmintic and also acts as a muscle poison in some small animals. The active principles in Hagenia abyssinica flowers are phloroglucinol derivatives, called kosins: kosotoxin, protokosin, kosidin, α-kosin and β-kosin. All are mixtures of isobutyryl, isovaleryl and 2-methylbutyryl side chain homologues of methylene-bis-pseudo-aspidinol. The kosins are presumably located in the glandular hairs.
Several plant species were used in Ethiopia to combat tapeworm infection, but kosso became the most popular and it became customary for people to have ‘a kosso day’ every 1–3 months. The extract is drunk before breakfast; about 0.5–3 hours later its laxative action starts. The head of the tapeworm (scolex) is seldom expelled, so the worm can regrow, hence the need to repeat the treatment every 1–3 months.
The efficacy of kosso as anthelmintic depends on dosage and the health of the patient. Strong doses of kosso can cause fainting, visual disorders or even death. Usually a dose of 8–16 g of dried flowers is taken, but some people use as much as 35 g. Although it is often stated that female flowers should be used, most tests reveal no difference in effect between male and female flowers. They can be as effective as the chemical anthelmintics dichlorophen, niclosamide and praziquantel. Side effects may include irritation of the gastrointestinal tract, salivation, nausea, headache, fainting spells, general weakness and diarrhoea. Some believe that side-effects are more severe when male flowers are used, and that male flowers have greater emetic activity. Health organizations currently discourage the use of kosso because the dosage of the active principle cannot be controlled by using the flower extract. In mice, doses up to 16 times the lethal dose by the intraperitoneal route produced no observable toxicity by the oral route; high doses affected peripheral vision in chicken. In-vitro tests have shown cytotoxic effects against carcinomous cells. Niclosamide (trade name 'Yomesan') is probably the best chemical medicine against tapeworm. It is effective against most types of tapeworm in the gut, but not against cysts outside the gut.
The sapwood is creamy-yellow; the heartwood dark red to red-brown, soft and moderately heavy (560–750 kg/m³ at 12% moisture content). The wood is usually straight-grained with occasionally some silver grain when cut radially. Kosso wood is not durable, and is subject to attack by borers and termites. Distortion during air drying may be severe. Average from green to 12% moisture content is 1.6% radially and 4.0% tangentially, and from green to oven dry 2.8% radially and 6.3% tangentially. The wood is fairly easy to saw. Planing may be difficult due to interlocked grain, but the moulding, boring and turning are satisfactory. Pre-boring before screwing is essential. Nail-holding power is high. The heartwood is very resistant to impregnation.
Adulterations and substitutes
Finely powdered kosso can easily be adulterated by any other brownish powder, whereas intact flower parts are very distinctive and cannot be adulterated. In Ethiopia, there are many plants with anthelmintic activity; fruits of Embelia schimperi Vatke (‘enkoko’) are most often used here as a substitute for kosso.
Dioecious, small to medium-sized tree, up to 20 m tall; bole rarely straight, up to 60(–220) cm in diameter; bark pale red-brown, flaky; crown wide, umbrella-shaped; young branches densely covered with short, villous hairs and long, erect, silvery, soft, often glandular hairs turning reddish-green, with ring-like, long persisting leaf scars. Leaves alternate, imparipinnate, up to 50 cm long; petiole up to 15 cm long, with 2, up to 1.5 cm wide, thin, leafy lateral wings (adnate stipules) at base surrounding the twig as a sheath; leaflets up to 17, alternate to subopposite, subsessile, narrowly oblong to elliptical, 9–15 cm × 2–5 cm, obliquely obtuse at base, acuminate at apex, margin serrate and long silky hairy, the teeth usually ending in a thickened gland, pinnately veined with veins prominent below and having long silky hairs; much smaller, suborbicular leaflets up to 2.5 cm in diameter may occur alternating with the normal leaflets. Inflorescence a terminal, drooping, much-branched, many-flowered panicle up to 60 cm × 30 cm, yellowish, often bright red tinged; branches villous to long silky hairy, sticky, subtended by leafy bracts, rachis usually zigzag. Flowers unisexual, regular; pedicel up to 3.5 mm long, densely hairy, subtending bracts clasping the pedicel at base, bracteoles reniform; hypanthium a conical, silky hairy tube 2–3 mm long, with 2 whorls of (4–)5 green or reddish tinged lobes (epicalyx and calyx), in male flowers epicalyx lobes smaller than calyx lobes, in female flowers larger and enlarging up to 10 mm long in fruit; petals (4–)5, vestigial, up to 1.5 mm long, alternating with the calyx lobes; stamens 15–20, filaments up to 3 mm long in male flowers, in female flowers rudimentary; pistils usually 2, free within the hypanthium, ovary with a tuft of hairs at top, style subfiliform, stigma capitate, usually only one ovary per female flower developing to fruit, in male flowers functionally sterile. Fruit a globose to ovoid achene up to 2.5 mm in diameter, with a thin, papery, pale to brown pericarp, white-hairy at top, enclosed by the dry persistent hypanthium with the epicalyx serving as wings. Seed subglobose to subovoid, only slightly smaller than the fruit, usually with a wrinkled, brown, glabrous testa.
Other botanical information
Hagenia is monotypic and very characteristic with its dioecism, pinnate, silky leaves and large, drooping inflorescences.
Wood-anatomical description:
- Macroscopic characters:
Heartwood dark red to red-brown, indistinctly demarcated from the creamy-yellow sapwood which may be up to 5 cm wide. Grain straight or interlocked. Texture fine. Growth rings indistinct. Radial surface sometimes with slight silver grain figure.
- Microscopic characters:
Vessels diffuse, 5–8/mm², solitary or in radial pairs, sometimes clustered; perforations simple. Parenchyma absent or indistinct. Rays 1–2/mm, broad, up to 1.5 mm high, homocellular or heterocellular with 1–2 rows of square cells. Gummy deposits abundant.
Growth and development
Individual Hagenia abyssinica trees often belong to the same or only a few size classes and are presumably the same age. It has been assumed that Hagenia abyssinica has a regeneration cycle associated with heavy forest fires. Crucial by clearing the area of competitive plants and heating the prospective seedbed. Mature Hagenia abyssinica trees are tolerant of fire, and heavy fires create ideal germination conditions for the small wind-dispersed seeds. Hagenia abyssinica is unable to regenerate in areas suffering from a high level of grazing. Young trees have poor competitive ability.
Individual trees are either male or female, but sometimes polygamous. In Ethiopia, flowering occurs during the dry season between October and February; on sunny days the flowers are much visited by bees.
Hagenia abyssinica occurs in montane rain forest and evergreen bushland, at altitudes of (2000–)2400–3400(–4300) m where annual rainfall ranges between 1000-1600 mm. On Mt. Kenya, it is dominant in the zone above bamboo thickets, between 2900–3400 m, where it occurs in association with Hypericum revolutum Vahl, Juniperus procera Hochst. ex Endl. and Gnidia glauca (Fresen.) Gilg. At these altitudes forest fires are rare, but occasional severe fires can occur during drought. In Ethiopia, Hagenia abyssinica is a dominant tree in subhumid montane woodland (rainfall up to 1250 mm per year). In humid montane woodland (rainfall up to 1600 mm per year), it occurs in association with the dominant tree bamboo Sinarundinaria alpina (K.Schum.) C.S.Chao & Renvoize, together with Schefflera volkensii (Engl.) Harms, Hypericum spp., Ilex mitis (L.) Radlk. and Nuxia congesta R.Br. ex Fresen.
Propagation and planting
Seed can be stored dry without special requirements for 0.5–1 year. Germination is about 40-60% after 2–3 weeks from sowing. The seed is very light: 400–500 seeds per gram. The tree is occasionally planted around churches and villages. Large-scale cultivation is unknown. In agricultural areas, Hagenia abyssinica can be found scattered in fields because it is not usually cut down.
In agroforestry systems in the southern highlands of Tanzania, trees grown or retained for shade are pruned once a year, about 50% of the foliage being removed.
Inflorescences are collected mainly from the wild, dried and stored, and can be used throughout the year.
No yield data are available. Only small numbers of flowers are needed per treatment; wild populations of Hagenia abyssinica easily provide the necessary quantities.
Handling after harvest
The powdered flowers are soaked overnight in water, honey-beer, or other sweetened fluids, to counteract the bitter taste. In Ethiopia, kosso is often taken with other plants to render its action more agreeable, e.g. with Malva verticillata L. (all parts), Linum usitatissimum L. (seeds) or Zehneria scabra (L.f.) Sond. (whole plant), or mixed with other anthelmintic plants, e.g. Phytolacca dodecandra L'Hér. (fruits and roots), Croton macrostachyus Hochst. ex Delile (bark) and Olea europaea L. (leaves).
Genetic resources
Hagenia abyssinica is widely distributed in montane Africa and not endangered. Collection of inflorescences for medicinal purposes does not greatly affect the plants. However, in locations with high population and cattle pressure the species is now rare or has disappeared (often cut for firewood purposes). No germplasm collections are known. Living collections and other conservation measures are strongly recommended.
In the southern highlands of Tanzania, Hagenia abyssinica is a protected tree. A royalty fee is required for a licence to exploit it. Consequently, few trees have been planted since the mid-1980s when the laws were more strictly enforced - an unfortunate result of well-intentioned conservation laws.
It is difficult to predict the medicinal future of Hagenia abyssinica. As long as tapeworm infestation occurs in remote areas (e.g. in Ethiopia) only equally cheap substitutes will reduce the use of kosso. In the long term, the crude drug will disappear from use as a result of restrictions on use. Commercial kosin extraction from flowers depends on quality, demand and price. Pharmacological research is underway in Ethiopia. Hagenia abyssinica is worthy of protection and worth planting for its ornamental value.
Major references
• Bekele-Tesemma, A., Birnie, A. & Tengnäs, B., 1993. Useful trees and shrubs for Ethiopia. Identification, propagation and management for agricultural and pastoral communities. Technical Handbook No 5. Regional Soil Conservation Unit/SIDA, Nairobi, Kenya. 474 pp.
• Graham, R.A., 1960. Rosaceae. In: Hubbard, O.B.E. & Milne-Redhead, E. (Editors). Flora of Tropical East Africa. Crown Agents for Oversea Governments and Administrations, London, United Kingdom. 61 pp. (pp. 43–45)
• Jansen, P.C.M., 1981. Spices, condiments and medicinal plants in Ethiopia, their taxonomy and agricultural significance. Agricultural Research Reports 906. Centre for Agricultural Publishing and Documentation, Wageningen, the Netherlands. 327 pp.
• Kloos, H., Tekle, A., Yohannes, L., Yosef, A. & Lemma, A., 1978. Preliminary studies of traditional medicinal plants in nineteen markets in Ethiopia: use patterns and public health aspects. Ethiopian Medical Journal 16: 33–43.
• Lange, S., Bussmann, R.W. & Beck, E., 1997. Stand structure and regeneration of the subalpine Hagenia abyssinica forests of Mt. Kenya. Botanica Acta 110: 473–480.
• Lemordant, D., 1972. Histoire et ethnobotanique du kosso. Journal d’Agriculture Tropicale et de la Botanique Appliquée 19: 560–582.
• Woldemariam, T.Z., Linley, P.A. & Fell, A.F., 1990. Phytochemical studies on male and female flowers of Hagenia abyssinica by column chromatography, thin-layer chromatography and high-performance liquid chromatography. Analytical Proceedings 27: 178–179.
Other references
• Arragie, M., 1983. Toxicity of kosso (Hagenia abyssinica), 1: acute toxicity in mice. Ethiopian Medical Journal 21: 89–93.
• Arragie, M., Metzner, J. & Bekemeier, H., 1983. Antispasmodic effect of Hagenia abyssinica. Planta Medica 47: 240–241.
• East, R. & Thurow, T., 1999. Challenging tradition: well-intentioned conservation laws in Tanzania are hampering age-old practices. Agroforestry Today 11: 1–2, 8–10.
• Lounasmaa, M., 1977. Dérivés phloroglucinoliques d’Hagenia abyssinica. 4. Résonance magnétique nucléaire du 13C de la kosotoxine, du pseudo-aspidinol et de l’alpha-kosine. Acta Chemica Scandinavica, Series B, 31: 77–80.
• Lounasmaa, M. & Varenne, P., 1978. Dérivés phloroglucinoliques d’Hagenia abyssinica. 5. Spectrometrie de masse en ionisation chimique de la kosotoxine, de la protokosine et de l’alpha-kosine. Planta Medica 34: 153–159.
• Lounasmaa, M., Widén, C.J. & Huhtikangas, A., 1973. Phoroglucinol derivatives of Hagenia abyssinica. Phytochemistry 12: 2017–2025.
• Lounasmaa, M., Widén, C.J. & Huhtikangas, A., 1974. Phoroglucinol derivatives of Hagenia abyssinica. 2. The structure determination of kosotoxin and protokosin. Acta Chemica Scandinavica, Series B, 28: 1200–1208.
• Lounasmaa, M., Widén, C.J. & Huhtikangas, A., 1974. Phoroglucinol derivatives of Hagenia abyssinica. 3. Reductive alkaline cleavages of kosotoxin and protokosin, and of aspidin BB (Dryopteris assimilis). Acta Chemica Scandinavica, Series B, 28: 1209–1218.
• Low, G., Rogers, L.J., Brumley, S.P. & Ehrlich, D., 1985. Visual deficits and retinotoxicity caused by the naturally occurring anthelmintics Embelia ribes and Hagenia abyssinica. Toxicology and Applied Pharmacology 81: 220–230.
• Madaus, G., 1938. Lehrbuch der biologischen Heilmittel. Abteilung 1: Heilpflanzen. Reprint 1976. Georg Olms Verlag, Hildesheim, Germany. pp.1693–1696.
• Medical Economics Company, 1998. Physicians’ Desk Reference (PDR) for herbal medicines. Montvale, United States. p. 885.
• Pankhurst, R., 1972. Remedius Prutky’s 18th Century account of Ethiopian taenicides and other medical treatment. Ethiopian Medical Journal 10: 3–6.
• Pankhurst, R., 1975. Historical anecdote: Dr. A. Brayer and Europe’s discovery of kosso. Ethiopian Medical Journal 13: 29–34.
• Pankhurst, R., 1979. Europe’s discovery of the Ethiopian taenicide - kosso. Medical History 23: 297–313.
• Rokos, L., 1969. Eye complications in poisoning caused by kosso (Hagenia abyssinica). Ethiopian Medical Journal 7: 11–16.
• Utilisation Section Forest Division in Moshi, 1963. Hagenia abyssinica. Timbers of Tanganyika. Utilisation Section Forest Division, Moshi, Tanzania. 4 pp.
• Werner, D., Thumann, C., Maxwell, J. & Pearson, A., 2001. Where there is no doctor. A village health care handbook. SHAMA Books, Addis Ababa, Ethiopia. 465 pp.
• Woldemariam, T.Z., Fell, A.F. & Linley, P.A., 1990. Chromatographic and spectroscopic studies on the constituents in male and female flowers of Hagenia abyssinica. Journal of Pharmaceutical and Biomedical Analysis 8: 859–865.
• Woldemariam, T.Z., Fell, A.F., Linley, P.A., Bibby, M.C. & Phillips, R.M., 1992. Evaluation of the anti-tumour action and acute toxicity of kosins from Hagenia abyssinica. Journal of Pharmaceutical and Biomedical Analysis 10: 555–560.
Sources of illustration
• Jansen, P.C.M., 1981. Spices, condiments and medicinal plants in Ethiopia, their taxonomy and agricultural significance. Agricultural Research Reports 906. Centre for Agricultural Publishing and Documentation, Wageningen, the Netherlands. 327 pp.
P.C.M. Jansen
PROSEA Publication Office, Wageningen University, P.O. Box 341, 6700 AH Wageningen, the Netherlands
Getachew Aweke
P.O. Box 4278, Addis Ababa, Ethiopia

L.P.A. Oyen
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, the Netherlands
R.H.M.J. Lemmens
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, the Netherlands
Associate Editors
S.D. Davis
Centre for Economic Botany, Royal Botanic Gardens, Kew, Richmond, Surrey TW9 3AE, United Kingdom
M. Chauvet
INRA Communication, 2 Place Viala, 34060 Montpellier, Cedex 1, France
J.S. Siemonsma
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, the Netherlands
M.M. Spitteler
Het Hoge Stuk 19, 8413 KL Oosterwolde, the Netherlands
Photo Editor
E. Boer
PROTA Network Office Europe, Wageningen University, P.O. Box 341, 6700 AH Wageningen, the Netherlands

Correct citation of this article:
Jansen, P.C.M. & Getachew Aweke, 2002. Hagenia abyssinica (Bruce) J.F.Gmel.. Record from Protabase. Oyen, L.P.A. & Lemmens, R.H.M.J. (Editors). PROTA (Plant Resources of Tropical Africa / Ressources végétales de l’Afrique tropicale), Wageningen, the Netherlands.
Distribution Map Hagenia abyssinica – wild

1, part of flowering branch; 2, female flower; 3, male flower; 4, fruit
Redrawn and adapted by M.M. Spitteler

tree habit

leafy branch



habit of flowering tree