Orbea melanantha (Orbeopsis melanantha) known earlier as the 'Caralluma with black flowers', is a distinct stapeliad characterized by stout stems 80-100 mm tall, the denticles on the stem teeth being very prominent on young sterns, but as the stems thicken the denticles are reduced to scars. Orbea melanantha is distinguished from all other species of Orbea, except Orbea lutea, by its dense clusters of more or less simultaneously opening, uniformly coloured, dark red to almost black, and fairly large flowers (50 mm across).
Cultivation and Propagation: It is an easy blooming plant when mature that require moderately watering through the growing season but enjoy plenty of water and some fertiliser in hot weather, this helps them to flower freely. Water more sparingly in winter according to temperatures. But, as with most asclepiads, it is unwise to leave them wet in cold weather. Winter care presents no problems at 5°C with plenty of light. Since roots are quite shallow, use a cactus mix or add extra perlite or pumice to regular soil potting soil. A gritty, very free-draining compost is suitable, and clay pots help the plants to dry out between watering. Sun Exposure: Partial sun or light shade Pest and diseases: Stapelia species vary in their susceptibility to rotting, but are generally fairly easy to grow, especially if kept pest-free. They are very susceptible to stem and root mealy bugs, and damage from these may well initiate fungal attack. If you do have problems with a stem or with basal rotting, you can reliably isolate the healthy parts, dry them off, and re-root them in moist compost. Cultural Practices: Re-pot every 2 years Propagation: Easiest with stem cuttings. Allow cuttings to dry a day before planting. Stems must be laid (Not buried) on gritty compost and will then root from the underside of the stems. It can also be increased from seeds sowing in spring in moist, sandy peat moss. Potting medium: Since roots are quite shallow, use a cactus mix or add extra perlite or pumice to regular soil potting soil. A gritty, very free-draining compost is suitable, and clay pots help the plants to dry out between watering.