Half of South Africa’s wetlands have been destroyed and those that remain are the most threatened of the country’s ecosystems (Driver et al., 2012). One cause of the wetlands’ reduction can be attributed to the spread of invasive species. Certain alien plants consume larger quantities of water than indigenous species (Gorgens and van Wilgen, 2004). Those invaders introduced to upper catchments spread quickly and reduce the flow of water. This limits water available downstream to wetlands, thus reducing their distribution and function (Richardson and van Wilgen, 2004). As freshwater supply in South Africa is dependent upon wetlands, invaders that restrict water to these areas in turn threaten the country’s already stressed water supply (Turpie et al., 2008). Therefore in order to secure the future of South Africa’s water sources, it is important to manage those alien plants which diminish wetlands.