A chronicle of alien medicinal plants used as traditional medicine in South Africa, and their status as invasive species

South Africa's colonial past has shaped its environmental history, including introductions of alien plants. Indentured Indian labourers, mainly from Tamil Nadu, that were brought to South Africa in the 1860s, acquired knowledge of Zulu healing practices and plants. This translocation of traditional medical knowledge (mostly Ayurvedic), and the adoption of new plants and traditions of practice, led to these migrants opening up some of the first muthi (traditional medicine) shops in South Africa, and also to importing and incorporating Indian medicinal plants within South African healing traditions. Given this role of traditional medicine in the introduction of alien plant taxa, we gathered data on them from published literature (including market surveys) and from a survey of 77 muthi outlets in three South African cities. There were 301 alien taxa from 76 families, of which 81 taxa were recorded in trade. Sixty-nine of the traded taxa were identified to species, of which 20 have a declared legal status requiring some form of control. Of the 81 traded taxa, 44% were sold in a non-viable form and 29% were seeds or fruit that could be germinated; the remaining 28% were sold as live plants. Seeds of these alien taxa constituted the greatest quantity and most widely traded plant part of the taxa recorded. The survey of muthi outlets generated 36 alien plant taxa, of which 26 were new records in the trade. Plant origins recorded in this survey revealed that 41% of plants were harvested in South Africa, 35% imported from India, and 24% were of unknown origin. The importance of this trade as a pathway for introduction of alien species is discussed