The great majority of melastome species live in the Americas. Tropical Africa has comparatively few, and Dissotis and its close relatives are among the most conspicuous. They also provide a good example of how genus boundaries change as botanists learn more.
Quick facts. Family: Melastomataceae. Range: tropical Africa, with some species naturalised elsewhere. Habitat: wet grassland, stream banks, forest edges and disturbed ground. Growth form: from creeping herbs to large shrubs. Flowers: bright pink to purple, with four or five petals.
What Dissotis looks like
Species traditionally placed in Dissotis include sprawling herbs and sturdy shrubs. The flowers are large for the size of the plant, usually in strong magenta, pink or purple, with four or five petals and prominent curved stamens. The leaves have the usual melastome pattern of strong longitudinal veins, and are often rough or hairy to the touch.
One species, often sold as Dissotis princeps, is a large shrub with showy purple flowers that resembles Tibouchina and has been grown in warm gardens. The creeping Dissotis rotundifolia, in contrast, forms a low mat and has been used as a ground cover.
A genus that has been rearranged
Dissotis once held a large number of species, but molecular and morphological studies showed the group was not a tidy natural unit. Many species were moved to other genera, and Heterotis is now widely used for a number of them, including the creeping plant formerly known as Dissotis rotundifolia, often listed today as Heterotis rotundifolia. Garden centres and older books still use the earlier names, so you may meet either.
This is a good example of how plant names respond to evolutionary relationships. The same thing happened to Tibouchina and Pleroma. If you are unsure which name is current, see how to check an accepted name.
Ecology
Dissotis and Heterotis typically grow in places that are wet at least part of the year: marshy grassland, stream edges, damp clearings. They often flower prolifically in sunny, open sites. Bees visit the flowers and collect pollen by vibrating the anthers, in the manner described in buzz pollination in melastomes.
Naturalisation
Some of the creeping species have been introduced to other tropical regions as ornamentals or ground cover and have escaped cultivation. As with other melastomes that spread easily, anyone in a warm, wet climate should check local invasive species guidance before planting.
In cultivation
- Light: full sun to partial shade for good flowering.
- Soil: moist, acidic, well-drained soil rich in organic matter.
- Water: regular, never allowed to dry out for long.
- Frost: most species are tender and need protection below a few degrees above freezing.
- Pruning: trimming after flowering keeps shrubs compact and encourages new growth.
Takeaways
Africa is not the family's stronghold, but its melastomes are distinctive and ecologically important in wet habitats. The genus history is a reminder to look at current names when researching or buying a plant.