Plant 357

Stapelia species (Apocynaceae)

Carrion flower

In 1737, the Swedish botanist Carolus Linnaeus named the genus Stapelia in honour of the early seventeenth-century Dutch physician and botanist Johannes van Stapel. Popular common names, such as carrion flower and starfish flower, reflect the foul odour of rotting meat produced by the flowers of most species, or their shape.

Native to southern Africa, Stapelia species occupy a wide range of habitats but most are found in arid areas. They are often found shaded by other plants with adaptations for living in arid environments. Their succulent, angular, green stems are laterally flattened with rows of warts along each edge that bear the remnants of small, short-lived leaves. Succulence and the absence of leaves helps to conserve water, whilst photosynthesis happens in the stem.

The main pollinators of Stapelia species are flies that often show specialised associations with one or a few species. Pollinators are attracted to the colour and pubescence of the flowers, along with the smell, which mimics rotting animal corpses; sometimes flies will even lay their eggs on the flowers they visit. At the centre of each flower, the male and female flower parts are found within a rigid, star-like structure, which is surrounded by five grooves that may temporarily trap pollinators. As flies move around the flower, searching for places to lay eggs or to feed on the nectar, they are guided into the grooves, where wax-covered packages of pollen (pollinia) are located. The pollinia are positioned such that they may easily become trapped on the legs or head of the pollinator as it tries to free itself from the flower. Once freed, pollinators may visit other flowers, effecting cross pollination when they move. After successful pollination, each flower produces two horn-like structures called follicles. Over about a year, follicles mature and eventually splits along one side to reveal seeds adapted for wind dispersal; they are flatted and capped with a tuft of hairs called a coma.

Flowers size varies among Stapelia species, with diameters ranging from about 6 mm to 400 mm. The largest blooms are found on the appropriately named Stapelia gigantea. In the wild, this species can form clumps up to two metres across, with each flower bud expanding like a balloon until it breaks open to release its putrid odour.

In cultivation, Stapelia species do best in well-drained, gritty compost. They should be watered sparingly – only when they start to become flaccid.

Further reading

Jürgens, A et al. 2006. The chemical nature of fetid floral odours in stapeliads (Apocynaceae‐Asclepiadoideae‐Ceropegieae). New Phytologist 172: 452-468.

Kunze, H 1991. Structure and function in asclepiad pollination. Plant Systematics and Evolution 176: 227-263.

Meve, U and Liede, S 1994. Floral biology and pollination in stapeliads - new results and a literature review. Plant Systematics and Evolution 192: 99-116.

Louisa Hall