How is it possible that a tree with such attractive flowers should bear fruits with such an awful stench?
Cladostemon kirkii is a deciduous tree up to 6 m tall. The bark is yellowish and grey, rough, adhering, marked by narrow fissures forming thin scales. The leaves arise singly at each node, and each has three leaflets; the common petiole is 50-200 mm long. The blade of each leaflet is 40-150 x 20-70 mm, ovate to elliptical, widest above or below the middle, with narrow tips and bases, and the surface is hairy below.
Flowers are borne in spikes at or near the tips of branches. There are 4 free, narrowly ovate sepals which are much smaller than the petals, 15-30 x 1.5-5 mm. There are 4 free, ovate petals, white with pink veins; a large pair 35-45 x 25-35 mm, and a smaller pair15--30 x 1.5--5 mm. The common stalk bearing the stamens and ovary is 90-130 mm long.
The fruit is fleshy, buff-brown and evil-smelling even when young; 170-220 x 70-120 mm, gourd-shaped. The seeds are mid-brown, 8-13 mm long and wide.
As may be expected for a tree whose range is so wide in tropical Africa (see below), the survival of the Tonga kierie is under no known threat, and it does not feature at all in SANBI's plant Red Data lists.
Distribution and habitat
The Tonga-kierie occurs in the East African region from near St. Lucia in Zululand (Kwazulu-Natal) to the Kilifi District, north of Mombasa in Kenya. It spreads from the coast inland as far as Katanga Province of the Democratic Republic of the Congo. It is a tree of lowland dry forest, woodland and secondary scrub, according to Elffers et al. (1964), and may therefore be expected to be at least moderately drought tolerant, but sensitive to cold and unable to endure frost.
Derivation of name and historical aspects
Cladostemon is a genus consisting of the single species described here. The name is derived from the Greek words klados, a branch and stemon, a stamen, and indicates that the stamens branch off a long and conspicuous androphore; this structure also holds the gynophore with the ovary at its tip, well away from the rest of the flower. The specific epithet commemorates the fact that Sir John Kirk (1832-1922) made the first recorded collection and observations of this tree in the Tete District of Mozambique, while accompanying David Livingstone's expedition down the Zambezi. Kirk went on to become British Consul in Zanzibar, where he lived and botanized for many years. He is commemorated in the names of many plant species, as well as a genus and a scientific journal, both called Kirkia.
The family Capparaceae, to which Cladostemon belongs, includes 39 genera and 650 species, mostly resident in warm, dry places. The genus Cleome provides several garden ornamentals, and Capparis spinosa is grown for its flower-buds, which are pickled and sold as capers.
As mentioned below, the roots are eaten by bush pigs. The size and form of the fruits suggests that they would be eaten by large, herbivorous mammals which, presumably, interpret the smell very differently to the way humans do. In the absence of any evidence, one wonders about the possibility of the seeds being dispersed by elephants, bush pigs or rhino. The flowers are sweetly scented, with white petals, which is classically what one finds in cases of pollination by night-flying creatures. The long androgynophore holding both stamens and stigmas far from the rest of the flower suggests at least a partial adaptation to bat rather than moth pollination, though the sweet scent suggests the reverse. Clearly, there is scope for someone to make observations to determine which of these actually does pollinate these trees. It is also possible that the trees are pollinated co-incidentally by bats hunting insects which are attracted by the scent of the flowers.
Uses and cultural aspects
Williams (1992) reports a ceremonial use of plants in Mozambican burial ritual, and a medicinal use in treating ophthalmia in the same country. The wood is reported (Killick 1970) to be brittle, and there are no accounts of its usefulness. Pooley, quoted by Williams (1992), reports that in Ndumu Game Reserve, bush pigs grub up the roots and eat them, and the trees coppice where the roots are damaged.
It is curious that two of the flora accounts cited in the references (Elffers et al. 1964 and Wild 1960) make no mention of the egregious smell of the fruits, but those who have smelt them not only do not forget the stench, but will go a long way to avoid repeating the experience.
Growing Cladostemon kirkii
If your garden is less than the size of a small country, your neighbours will hate you passionately and with good reason for the smell of the fruits. As a garden plant, this tree belongs only in the deepest of no-go areas, and the best advice for a private gardener is rather plant something else. It therefore comes as no surprise that young plants are not listed in any of the handbooks for the Botanical Society annual Durban plant sale.
However, the tree books and Flowering Plants plate cited below suggest that this tree is a worthy subject for frost-free gardens large and small. It is said to be easily grown from seed, cuttings and root division, and desirable for the texture, form and sweet scent of the flowers. Quite how one prevents fruit set remains unrecorded.
If pressed for a suitable garden situation for this tree, I would be inclined to say somewhere else, far away, unless the gardener has no sense of smell and a passionate hatred of the neighbours. In a botanical garden, one might look for in or on the edge of a thicket of trees which likewise require a warm dry climate, such as many of the African thorn trees. The undergrowth in such a thicket would probably be semi-succulent and tough.
"On the other hand, I have it on good authority (Elsa Pooley, pers. comm.) that the fruits are only objectionable when detached from the tree. As the form of the tree is attractive and the flowers sweetly scented, Mrs Pooley is strongly in favour of this small tree as a garden subject in warm areas. It is only necessary to remember not to touch the fruits when they are present."
No pests or diseases are known for this tree.
References and further reading
- Balkwill, K., Boon, R., Coates Palgrave, M., Glen, H., Jordaan, M., Lötter, M., Schmidt, E. & Thomas, V. 2004. SAPPI Tree spotting lifer list. Jacana, Johannesburg.
- Coates Palgrave, M. 2002. Keith Coates Palgrave Trees of southern Africa, edn 3. Struik, Cape Town.
- Elffers, J., Graham, R.A. & DeWolf, G.P. 1964. Cladostemon. Flora of tropical East Africa. Capparidaceae : 70-72. Crown Agents, London.
- Glen, H.F. 2004. SAPPI What's in a name? Jacana, Johannesburg.
- Killick, D.J.B. 1970. Cladostemon. Flora of southern Africa 13: 140-142. Botanical Research Institute, Pretoria.
- Mabberley, D.J. 2002. The plant-book. Cambridge University Press, Cambridge.
- Pooley, E.S. 1993. The complete field guide to trees of Natal, Zululand and Transkei. Natal Flora Publications Trust, Durban.
- Von Breitenbach, F. 1965. The indigenous trees of southern Africa. Government Printer, Pretoria.
- Wild, H. 1960. Capparidaceae. Flora zambesiaca 1: 194-245. Crown Agents, London.
- Williams, R. 1993. Cladostemon kirkii. The Flowering Plants of Africa 52: t. 2079.