The history, morphology, ecology and conservation status are described of Gerrardanthus tomentosus Harv. ex Hook.f., considered the world's rarest caudiciform species. It is known from only five collections over the past 125 years and from three sites in the Durban area, all endangered by urbanisation and Zulu herb gatherers. Eleven known plants exist within a designated nature reserve, but are undersized and overgrown by alien vegetation. It is a clear candidate for conservation in cultivation, and cuttings and seedlings are being successfully raised.