Asclepias: Greenhouse Plants
C – cool, minimum of 7°C (45°F) / W – warm, minimum of 13°C (55°F)
The two main species suitable for greenhouse cultivation are from different sides of the world. Asclepias physocarpus from South Africa enjoys cool conditions and will make a 2m (6 ft) shrub if allowed to. Its small white flowers are attractive to butterflies but the chief attraction lies in its inflated seed pods, about 5 cm (2 in) long and covered in soft bristles. They make an unusual addition to a dried flower arrangement. It flowers and pods in late summer so any pruning is best done in the autumn. During the lower temperatures of winter water less and cease feeding. A. curassavica is the Blood Flower from tropical America and needs a winter minimum of 10°C (50°F) to do well. A much smaller, less shrubby plant, it has bright orange flowers through summer and autumn. There is a white form A. c. ‘Alba’. Seed is produced in long pods and, in common with other members of the family (Hoya, Stephanotis), is hairy. Seed of both plants is easy to germinate, in fact having once planted A. curassivica in a greenhouse border it invariably seeds itself every year.