Wahlenbergia capensis, the Cape bluebell, is a member of the Campanulaceae (the bellflower family). Its showy flowers start appearing from early spring, decorating the sandy flats and lower mountain slopes of the Cape Floristic Region.
Wahlenbergia capensis is an erect or ascending, single- or multi-stemmed hairy annual herb, between 14 and 50 cm tall. The leaves are alternate, sessile, obovate to narrowly elliptic or lanceolate. Leaves are hairy with strongly toothed undulate margins.
Flowers are solitary or 2-4 per stem on long flower stalks. The corolla is bell-shaped, bluish-green but dark blue in the centre and often with black spots on the inside of the lobes. The calyx consists of 5 spreading or erect triangular sepals which are fused to the densely hairy hypanthium. Stamens are free, 5, and inserted at the base of the corolla. Filaments are dark blue, the base is expanded and ciliate with rounded shoulders forming a filament dome. The pistil comprises an inferior, 5-loculary ovaryand a dark blue style covered with pollen-collecting hairs below the 5 broad stigmatic lobes. In each locule are numerous axile ovules.
The fruit is a capsule, which dehisces by apical valves.
Flowering time: September to December.
W. capensis is not threatened.
Distribution and habitat
This species is widespread in and restricted to the Western Cape Province in South Africa, from Clanwilliam to Knysna. However, it has been introduced to south-western Australia where it has become a noxious weed.
In the Western Cape it grows on sandy flats and sandstone slopes, and in disturbed habitats such a roadsides and cultivated land.
Derivation of name and historical aspects
The species was first described by Linnaeus as Campanula capensis. Later the genus Wahlenbergia was established in honour of Georg Wahlenberg, a professor of botany at Uppsala University. It was then transferred to Wahlenbergia and designated as the type species of this new genus.
Wahlenbergia is the second largest genus in the Campanulaceae, comprising about 260 species of which the greatest diversity of species occurs in Africa, particularly in South Africa where about 170 species are known. It is also found in South America, Australia, New Zealand and southern Europe. The specific epithet, capensis, means from the Cape, referring to its distribution.
The annual life cycle favours the survival of this species at a time of massive habitat destruction. Large numbers of seed are produced in capsules which open through apical valves, allowing the seed to be dispersed when the capsule is shaken by the strong summer wind prevalent in the Cape. The capsule is also covered by coarse stiff hairs which easily attach to animals, facilitating dispersal of seed-filled capsules to suitable habitats.
Uses and cultural aspects
No cultural or other uses have been documented for W. capensis.
Growing Wahlenbergia capensis
Large stands of W. capensis make impressive displays in the wild. However, this self-seeding annual has apparently not been considered a suitable garden plant. Wahlenbergia undulata and W. rivularis from the summer rainfall regions of South Africa are found in gardens.
References and further reading
- Cupido, C. & Conrad, F. 1999. Bellflowers - Getting to know the South African bellflowers. Veld & Flora 85: 180-181.
- Leistner, O.A. (ed.). 2000. Seeds plants of southern Africa : families and genera. Strelitzia 10. National Botanical Institute, Pretoria.
- Smith, P.J. 1992. A revision of the genus Wahlenbergia (Campanulaceae) in Australia. Telopea 5: 91-175.
Compton Herbarium, Kirstenbosch