Roella glomerata with its large, white to pale blue flowers, is the only member of the South African endemic genus, Roella that is found outside the Cape Floristic Region.
Roella glomerata is a summer flowering, erect, branched shrublet, up to 600 mm tall. Leaves are numerous, linear-lanceolate, stiff, bristly, often with an axillary cluster of smaller leaves.
Flowers are regular, sessile, in dense heads at the tips of branches; bracts are leaf-like. The bell-shaped corolla is white to pale blue consisting of 5, deeply divided corolla lobes fused into a short tube. Similarly the hairless calyx has five lobes fused into a short tube. Stamens are five, free and inserted at the base of the corolla tube; filaments are expanded at the base to form a dome over a nectiferous disc; anthers are linear and attached to the filament at its base. The 2-locular ovary is inferior and crowned by the nectiferous disc; the style is rod-like with 2 glands at the base of a 2-lobed stigma. In each locule are numerous ovules. The fruit is a capsule which opens by an apical plug.
This species is currently listed as LC (Least Concern) in the Red List of South African Plants, which means that it is not considered to be under any risk of extinction. However, recent visits to known localities to study the species in the field, suggested the contrary. The remaining natural habitat of R . glomerata is rapidly declining as a result of urban expansion along the KwaZulu-Natal southern coast and areas around East London in the Eastern Cape. A revision of its conservation status could be necessary in the foreseeable future.
Distribution and habitat
Roella glomerata is endemic to South Africa and is the only Roella species occurring in the summer rainfall region. It can be found along the Eastern Cape and KwaZulu-Natal coast where it is historically known from East London to Durban. The species occupies sandy flats and grasslands at altitudes between 10 – 170 m.
Derivation of name and historical aspects
The name Roella, was given to the genus by Linnaeus in 1753, to honour the Dutch Anatomist, G. Roelle. The species glomerata was first described by Alphonse De Candolle in 1839, based on a collection of J.F. Drège from grasslands near a river mouth in Pondoland in the Eastern Cape. When De Candolle described the species he most likely derived the specific epithet from the tight arrangement of the flowers in a head-like inflorescence, which he referred to as ‘ floribus glomeratis '.
Roella glomerata is likely to have a similar pollination syndrome as for the genus as described in a separate article by the second author.
Uses and cultural aspects
In KwaZulu-Natal Roella glomerata is used to treat lower back pain.
Growing Roella glomerata
This species is not known to be cultivated as it cannot easily be propagated. However, its attractive white to pale blue flowers and foliage would make it a potential garden ornamental, or with its long stems, a cut-flower.
References and further reading
- Adamson, R.S. 1952. A revision of the genera Prismatocarpus and Roella . Journal of South African Botany 27: 93–166.
- Cupido, C. 2011. Roella . www.plantzafrica.com/plantqrs/roella.htm
- Cupido, C.N. & Nelson, L.J. 2012. Floral functional structure, sexual phases, flower visitors and aspects of breeding system in Roella ciliata (Campanulaceae) in a fragmented habitat. Plant Systematics and Evolution 298: 931 – 936.
- Leistner, O.A. (ed.). 2000. Seed plants of southern Africa: families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
- Raimondo, D., Von Staden, L., Foden, W., Victor, J.E., Helme, N.A., Turner, R.C., Kamundi, D.A. & Manyama, P.A. (eds). 2009. Red List of South African plants 2009. Strelitzia 25. South African National Biodiversity Institute, Pretoria.
Mischke Engelbrecht and Christopher Cupido