Adenia is a member of the family of passionflowers called Passifloraceae. It is native to Africa, Tanzania, Somalia, and Madagascar. This group of flowering plants gets its name from the Passiflora flower genus. It includes Passiflora edulis, which bears the edible passion fruit. Common climbing garden plants such as Maypop and Running Pop, which are known for their stunning, showy flowers, are included in this group as well. The variety of Adenia plants range from succulent, desert type plants, to tropical trees. Several varieties also have highly-toxic sap.
While this family of plants is known for the beautiful passionflower genus, it also consists of many caudiciform, or succulent varieties as well. These include several peculiar, odd looking plants with decorative stems. This type grows in the understories of rain forests and spreads by underground tubers. Some of these tubers grow to form an above-ground caudex — the stem and root base of the plant — with very thick trunks.
One of the most unusual types is Adenia pechuelli, which grows in Namibia. It has a caudex that can grow to more than a yard (91.44 cm) wide. With its wide, squatty looking branches, it resembles a hedgehog in appearance. To make them look even stranger, they often grow out of rock crevices.
While many Adenia plants are poisonous, one in particular is noted for its toxicity. Adenia digitata has the reputation of being the most poisonous plant in the world, and actually contains a cyanide compound. Great care should be used when pruning or handling any of these plants.
All varieties of Adenia are dioecious, meaning that the individual plants are either male or female. It is necessary to have one of each in order to produce seeds. For this reason, it is easier to propagate them by cuttings, though they frequently will not develop the thick caudiciform base using this method. Propagating by seed, however, will usually produce the thickened base.
Adenia grow in warm climates and will not survive temperatures below 45 degrees (13 Celsius). The passionflower species make good container plants, which will do well indoors with bright light and sandy, well-drained soil. The larger succulent types are much too large to attempt to keep indoors.
Many of the plants available in garden centers and nurseries are domesticated clones. The clones are usually designed to survive a larger range of growing conditions than their native counterparts. They can typically withstand more cold and moisture, and cannot be killed as easily as plants transplanted from their natural habitat.