Hoodia pronounced "who Dee ah" Gordonii is actually a succulent and technically different from a cactus, it is also know by the name "Xhoba". It belongs in the succulent family of Asclepiadaceae along with stapelia, stephanotis and vinca.
There are approximately 20 species in the genus of Asclepiadaceae. As it grows it forms multi-stemmed clumps 12 inches wide by 12 inches high and bears unpleasant-smelling, pale purple saucer-shaped flowers (3-4in) in diameter in red or purple brown. The plant grows to a mature height of six-feet and may survive for a century or more.
The Hoodia Gordonii plant originated in the southwestern part of Africa and grows best in the semi-arid areas of South Africa primarily the Kalahari. It has also been cultivated in semi-arid areas of China, Mexico and the US with limited success. In its native habitat it is extremely difficulty to identify because it looks similar to succulents of the same family of which there are 20.
Only an experienced botanist or as the case in South Africa with Hoodia Gordonii a San people can tell the difference, others wait for the plant to bloom in order to make an identification.
The San people of the Kalahari have also learned to eat the bitter-tasting plant to suppress their appetite and thirst when on long hunting expeditions. It takes the edge off appetite and thirst, and has enabled the hunters to respect their tradition of bringing home their entire catch, without eating of it on the way.