Solanum giganteum 

Jacq.

Family:
Solanaceae (nightshade family)
Common names:
healing-leaf tree, giant bitter-apple, red bitter-apple, red bitter-berry, thorny bug-tree (Eng.); geneesblaarboom, grootbitterappel, rooibitterbessie, doring-luisboom (Afr.); Icuba lasendle (Xhosa)


Berries of Solanum giganteum

This big shrub with its colourful, long-lasting berries and large leaves with silvery undersides, makes an unusual hedge or background plant.

Description
Much-branched shrub or small tree up to 6 m high. Branchlets with white, woolly hairs and stout, straight prickles up to 5 mm long. Leaves elliptic, margin entire, large, up to 250 x 90 mm, softly textured, dark green, glabrescent, becoming hairless/smooth above, velvety whitish/silver below; pedicels reflexed in flower, erect in fruit; large bract-like leaves are often present in the axils of the stem leaves. Flowers in many-flowered, branched, dense, terminal corymbs, faintly scented; corolla white, mauve to blue or purple, 15 mm in diameter, anthers yellow.Solanum giganteum Fruit a smooth, globose berry, 5-10 mm in diameter, green, ripening through orange to bright red, finally purplish red, remaining on the plant for at least six months. Flowers and fruit are often found on the same plant, even in the same inflorescence. Chromosome number: 2n = 24.
S. giganteum shows some resemblance to the declared invasive weed, S. mauritianum or bug-tree (luisboom) which is a native of South America. However, that species has no prickles, has yellow fruit, and is very densely velvety or felty hairy in almost all parts.

Distribution
This mostly montane species is widely distributed in Africa south of the Sahara, from the Cameroon to Ethiopia and down from eastern Africa to the Cape. It is also indigenous to southern India. In South Africa it has been recorded from all provinces except the Free State and Northern Cape. It also occurs in Swaziland but not in Namibia, Botswana or Lesotho. It is sometimes cultivated in Botanical Gardens and elsewhere, but is not known to become naturalized. In Australia it is known as African holly.
Habitat: The healing-leaf tree usually grows in dense to partial shade in forest margins and clearings, among trees and often on river banks and in other moist places. It is common in high rainfall areas, up to 2 000 mm annual rainfall. It can grow on steep or gentle slopes of all aspects and prefers humus rich, well-drained, brown or red, sandy or loamy soils, also stony soils. The geology has been described as granite, Swaziland rocks, middle Ecca sandstone.

Derivation of the name
Jaeger (1985) explains that the genus name Solanum is possibly connected to the Latin noun solamen, meaning a relief or comfort, assumed from the palliative effects of the nightshades. The species name giganteum refers to the fact that the healing-leaf tree is relatively speaking, a very tall member of the genus Solanum, where trees are quite rare.
The Solanaceae is an economically important family of about 2 600 species of plants, with its chief centre of diversity in Central and South America. This family contains many poisonous, medicinal and edible plants, and also several horticultural favourites as well as many weeds. Potatoes, tomatoes, green peppers and aubergines all belong to this family.

Solanum is a large, cosmopolitan genus of perhaps as many as 1 500 species; about 50 of these species are found in southern Africa and about 30 of them are indigenous. S. giganteum belongs to the section Giganteiformia (of the subgenus Leptostemonum) that Child defined in 1998. This is a group of about ten shrubs and small trees growing in the forest clearings and savanna of tropical and southern Africa as well as India and SriLanka. Their most important common characters are: a dense tomentum, entire discolorous leaves, small flowers, small red berries. S. giganteum appears on the official Tree List of South Africa (no. 669.4) and Zimbabwe (no. 1014).

Ecology
Specimens of S. giganteum have been collected in forests, woodland and grassland at a wide range of altitudes from 5-2 000 m. It can also occur as a weed in disturbed areas. It flowers in summer from October to April; fruiting specimens have been collected throughout the year, but mainly from December to July. Larger birds such as louries, doves and bulbuls feed on the fruit, particularly in late winter when food is in short supply.

Uses and cultural aspects
S. giganteum is a known medicinal plant, as indicated by its Afrikaans and English standardized common names. According to Watt & Breyer-Brandwijk (1962), the leaves were formerly used as a dressing for festering, open sores: the woolly undersurface being applied to cleanse the lesion and the smooth upper surface to heal it. The early Cape settlers also used an ointment (with fat) of the fresh juice of the berry and leaf for a similar purpose. Hutchings et al. (1996) record that the fruit is used for throat ulcers by the Zulu, Xhosa and Mfengu. Various chemical constituents typical of the Solanaceae have been isolated from this species e.g. solasodine from the fruit and leaves. The Xhosa and Mfengu use the berry to curdle milk.

Growing Solanum giganteum

This species is an attractive garden subject, mainly because of the clusters of bright red fruit. According to Nichols (2002), it can be used as a background plant in herbaceous borders; also as part of a hedge where it can be the focal point behind the tangle of thorny creepers or shrubs that form the bulk and body of the hedge. Seeds germinate easily when cleaned out of the fruit. Seedlings grow rapidly and the plant should be fruiting in the second year.

References

  • Child, A. 1998. Studies in Solanum and related genera (6). New infrageneric taxa for the genus Solanum L. (Solanaceae). Feddes Repertorium 109, 5-6: 407-427.
  • Hutchings, A., Scott, A.H., Lewis, G. & Cunningham, A.B. 1996. Zulu medicinal plants, an inventory. University of Natal Press, Pietermaritzburg.
  • Jaeger, P.-M.L. 1985. Systematic studies in the genus Solanum in Africa: 1-540. Ph.D. thesis, University of Birmingham. Unpublished.
  • Nichols, G. 2002. Add colour and life to your hedges. Farmer's Weekly, 10 May, Grow: 13.
  • Van Wyk, B. & Van Wyk, P. 1997. Field guide to trees of southern Africa. Struik, Cape Town.
  • Von Breitenbach, J., De Winter, B., Poynton, R., Van den Berg, E., Van Wyk, B. & Van Wyk, E. 2001. Pocket list of southern African indigenous trees: Including selected shrubs and woody climbers, 1st abridged impression of edn 4. Briza Publications & Dendrological Foundation, Pretoria.
  • Watt, J.M. & Breyer-Brandwijk, M.G. 1962. Medicinal and poisonous plants of southern and eastern Africa, edn 2. Livingstone, Edinburgh & London.

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Author: Mienkie Welman
National Herbarium, Pretoria
January 2004

 


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