Stapelia

Stapelia is a genus of low, clumping, leafless stem-succulents in the milkweed family Apocynaceae, native to the drylands of southern Africa. The genus is famous — or notorious — for its large, five-pointed, star-shaped flowers, which are often covered in fine hairs and produce a powerful carrion scent that has earned its members the common names carrion flower and starfish flower. These plants belong to the informal group of milkweed succulents known as stapeliads, and are among the most rewarding of all succulents to bring into bloom.

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Description

Stapelias form spreading clumps of soft, fleshy, four-angled stems that rise more or less erect from the base. The stems are typically green (flushing red or purple in strong light), toothed along their angles, and effectively leafless — photosynthesis happens in the stem itself, as it does in many desert succulents. Unlike true cacti, these teeth are soft and not spines; the resemblance is a case of convergent evolution between two unrelated families.

The flowers are the genus's whole reason for fame. Borne low on the stems, they are broadly star-shaped with five triangular lobes, ranging from a couple of centimetres to well over 30 cm across in the largest species. Colours run from ochre and tan to deep maroon, usually patterned with fine transverse wrinkles and fringed or coated with hairs. Most species emit a smell of rotting meat, sometimes remarkably strong, which — together with the flower's colour and texture — mimics carrion to attract the flies that pollinate them. Pollinated flowers develop the paired, horn-like seed pods (follicles) typical of the milkweed family, splitting to release seeds carried on silky parachutes of hair.

Distribution and habitat

The genus is centred on southern Africa, with the greatest diversity in South Africa, Namibia and Botswana, and outliers reaching further north and east. Stapelias are plants of arid and semi-arid country, typically growing in the shelter of rocks or beneath low shrubs where they gain some shade and a little extra moisture. In habitat they endure long dry periods and rely on their fleshy stems to store water through drought.

Notable species

Stapelia gigantea — the giant carrion flower, with enormous pale, red-lined star flowers that can span a dinner plate; one of the most widely grown species.
Stapelia grandiflora — large, dark, densely hairy flowers on robust stems.
Stapelia variegata — now often placed in the related genus Orbea (as Orbea variegata), a compact old-garden favourite with boldly mottled star flowers.
Stapelia hirsuta — very hairy, richly coloured blooms.
Stapelia flavopurpurea — smaller flowers noted, unusually for the genus, for a pleasant rather than foul scent.

Because the boundaries of Stapelia have shifted with study, several plants long grown under this name now sit in allied genera, most notably Orbea. Together with related stapeliad genera such as Huernia and Orbeanthus, they belong to the same broad group and are grown in much the same way.

Cultivation

Stapelias are among the easier stem succulents to keep, and free-flowering when happy. Grow them in a very free-draining, mostly mineral mix in a shallow, wide pot that gives the clump room to spread. They appreciate bright light with some protection from the harshest midday sun — deep shade produces weak, floppy growth, while excessive sun can scorch the soft stems.

Water regularly through the warm growing season, letting the mix approach dryness between waterings, then keep the plants much drier and cooler through winter to prevent rot. Overwatering, especially in cold conditions, is by far the commonest cause of loss: the fleshy stems rot readily at the base, often taking a whole clump with them. Keep them frost-free, as the soft tissue has little tolerance for freezing. See Watering and Repotting for general technique.

Propagation

Stapelias are very easily propagated from stem cuttings. Detach a healthy stem segment, let the cut end callus and dry for a few days, then set it on or barely into a gritty mix; it will usually root quickly in warm weather. Because clumps naturally sprawl and self-layer, dividing an established plant is another simple route. Fresh seed germinates readily too (see Propagation — seed), though seed-grown plants may vary and hybridise freely with related stapeliads.

Common problems

Stem rot — the signature Stapelia ailment, brought on by overwatering, a slow-draining mix, or cold wet winters; affected stems go soft, translucent and brown. Take healthy cuttings promptly to save a collection.
Mealybugs — white cottony insects that lodge between stems and around the roots; watch the base of the clump especially. See Pests and diseases.
Flower smell — not a fault but worth noting: a blooming plant can perfume a whole room with the scent of rotting meat, and may attract flies indoors. Many growers move plants outside or to a porch while in flower.
Weak, etiolated growth — thin, pale, leaning stems indicate too little light.

References

Horticultural information for growing these plants as ornamentals. Always confirm plant identification and any handling, grafting, or safety advice against authoritative sources before acting.