Dissotis princeps

(Kunth) Triana

Family:
Melastomataceae (tibouchina family)
Common names : purple dissotis, royal dissotis, wild tibouchina, purple wild tibouchina (Eng.); kalwerbossie (Afr.); sichobochobo, umpongamponga (Swazi)

Dissotis princeps

Dissotis princeps is an outstanding garden plant with magnificent flowers and decorative foliage. It is easy to grow, and is ideal for the water or vlei (marsh) garden, or for that difficult, permanently damp spot.

Description
Dissotis princeps is a soft, herbaceous shrub, 1.5 to 3 m tall. Young stems are angular and the whole plant is covered in short, bristly hairs. The leaves are large, 30-145 x 10-55 mm, egg-shaped to lance-shaped, and velvety, dark green above and paler to whitish underneath with 5 conspicuous veins from the base. Old leaves turn red.

White form

Large, ± 60 mm diameter, purple or occasionally white flowers are produced in showy terminal panicles. At Kirstenbosch they are in flower from mid to late summer until autumn, whereafter they are cut back and allowed to go dormant during winter. Further north in more tropical climates, they continue flowering through winter into spring.Calyx after petals fall.

The calyx is an ± 10 mm long tube with 5 lobes, dark reddish pink and covered in clusters of bristly hairs and knobby bumps, and it persists after the petals have dropped off. The spectacular inflorescence is multi-toned-the dark reddish pink calyx encloses the dark purple bud that opens to the paler purple, 5-petalled flowers with their purple and yellow stamens and purplish pink style.

The fruit is a capsule that develops inside the persistent calyx, releasing masses of very small seeds.

Dissotis has unusual stamens: firstly, when in bud, they are bent downwards and the anthers are partly hidden inside pockets between the calyx and ovary; secondly, when mature, the anthers shed their pollen through an apical pore; and thirdly, and more easily observed by a person without a dissecting microscope, the stamens are unequal.

 Flower close up showing stamens

Looking at a D. princeps flower, it first appears as if the two types of stamens are easy to spot and very clearly different-there is a bunch with what appear to be yellow anthers curving downwards on the top half of the flower, and a bunch with purple anthers curving upwards on the lower half. In fact, the yellow bits are not anthers at all, but an appendage on the filament. It also looks as if there are many stamens. There are in fact 10 stamens, attached just inside the rim of the calyx, in two rows: 5 alternate with the petals while the other 5 are attached opposite the petals. Why it looks as if there are more than 10 is because each stamen is made up of two parts: the ± 10 mm long yellow filament and the dark purple anther that is attached to the filament by a pinkish purple, jointed connective. At the point where the connective joins the filament there are two short, yellow horns-these are what appear to be yellow anthers. The actual anthers are dark purple and ± 10 mm long and crinkled when mature. All the anthers are fertile.The stamens of the opposite row have 5 mm long connectives-you can see them clustered in the middle of the flowers directly under the yellow filaments and horns. The stamens of the alternate row have longer 15 mm connectives-they are the large claw-like structures in the lower half of the flower. The style is ± 30 mm long, purplish pink with a yellow stigma.

See image of flower dissected to show unusual stamens

Distribution & habitat
Dissotis princeps occurs in marshy places, along streambanks and at the fringe of forests in KwaZulu-Natal, Swaziland, Limpopo, Botswana, Namibia, Mozambique, Zimbabwe, Zambia and Malawi.

 Derivation of the name & historical aspects
The genus name Dissotis is derived from the Greek dissos meaning two-fold, referring to the two different types of stamens. The species name princeps means most distinguished in Latin, perhaps the botanist who named it considered it to be the most distinguished species in its genus, on account of its long flowering period and showy inflorescence; princeps also means princely, which is possibly why it earned the common name of royal dissotis. It gets its common name of wild tibouchina from its close resemblance to the many cultivars of Tibouchina (sometimes still called by its old name Lasiandra ), that originated in South America and is grown in gardens all over the world. Both Dissotis and Tibouchina belong in the Melastomataceae, a family of ± 240 genera and 3 000 species that occur in the tropical and subtropical regions of the world, particularly in South America. In southern Africa, the family is represented by 5 genera and 11 species.

The genus Dissotis consists of ± 120 species in Africa, three of which occur in southern Africa, the other two southern African species are: D. canescens and D. pulchra of which only D. canescens can be seen at Kirstenbosch. It has smaller leaves and a less spectacular inflorescence than D. princeps. Two more southern African species that were in the genus Dissotis, viz. D. debilis and D. phaeotricha and their subspecies have been reclassified in the genus Antherotoma.

Uses & cultural aspects
The roots were formerly used to fatten calves. Certain tribes are said to have eaten the roots as an aphrodisiac. In KwaZulu-Natal it was eaten as a vegetable in times of starvation. This species is used in traditional medicine, probably in the same way as Dissotis canescens which is also eaten in times of famine, and the leaves, stems and roots are used to make a brew to prevent the development of certain unpleasant symptoms caused by drinking beer made from the new season's mealies, and the leaves are used to treat dysentery and diarrhoea.

Growing in Kirstenbosch

Growing Dissotis princeps

This handsome species is fast, easy and rewarding to grow provided it is planted in fertile, well-watered soil in a sunny position. It can be allowed to dry out completely and go dormant during winter and cut back almost to ground level and it will resprout strongly in the spring. It survives the wet Cape winters without difficulty and in tropical climates can be left unpruned and growing through the winter, but regular, heavy pruning keeps it neater and more bushy. It is cut back by frost but resprouts in the spring, and would probably not survive outdoors in climates colder than USDA Zone 9.( -7 to -1°C or 20 to 30°F)

Freshly opened flowersDissotis princeps is a must for any kind of water garden, planted in damp soil e.g. in the overflow from a pond or beside a stream. It can be planted in the regular garden or herbaceous border but to perform at its best it must be well-watered. It makes a good container plant but must be well fed and well watered.

Propagate by seed sown in spring or early summer. At Kirstenbosch, because they root so easily, we tend to propagate this species only by cuttings. We cut the plants back during winter and take stem cuttings from the resprouting spring growth in spring to early summer (Sept-Nov). Treat them with rooting hormone and place under mist and they root easily in approx. two weeks. Vegetative propagation also allows us to keep the white and purple colour forms distinct and separate.

References and further reading

  • Dyer, R.A. 1952. Dissotis princeps. The Flowering Plants of Africa 32: t. 1250.
  • Fabian, A. & Germishuizen, G. 1982. Transvaal wild flowers. Macmillan, Johannesburg.
  • Fox, E.W. & Norwood Young, M.E. 1982. Food from the veld: edible wild plants of southern Africa. Delta Books, Johannesburg.
  • Germishuizen, G. & Meyer, N.L. (eds). 2003. Plants of southern Africa : an annotated checklist. Strelitzia 14. National Botanical Institute, Pretoria.
  • Gibson, J.M. 1975. Wild flowers of Natal (coastal region). Natal Publishing Trust Fund, Durban.
  • Leistner, O.A. (ed.). 2000. Seed plants of southern Africa : families and genera, Strelitzia 10. National Botanical Institute, Pretoria.
  • Pooley, E. 1998. A field guide to wild flowers of KwaZulu-Natal and the Eastern Region. Natal Flora Publications Trust, Durban.
  • Smith, C.A. 1966. Common names of South African plants. Memoirs of the Botanical Survey of South Africa No. 35.

 

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Kirstenbosch National Botanical Garden
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