Alien InvasiveSalixspp. (Willows) in the Grassland Biome of South Africa

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Abstract
Roadside surveys of alien plant invaders in the grasslands of the Transvaal, Natal, Orange Free State and eastern Cape showed that several alien Salix species (willows) are naturalised along watercourses in these regions. Salix babylonica, the weeping willow, and S. fragilis, one of the basket willows, are the most prominent species. S. babylonica is the most widespread woody riverine invader in the grasslands of South Africa. S. fragilis (fide R.D. Meikle) is less widely distributed but prominent in the high grasslands of the north-eastern Orange Free State, southern Natal and north-eastern Cape. Both species have, in places, formed pure stands along whole river reaches. Although S. babylonica has been planted at dams and along riverbanks its extensive occurrence along watercourses is most likely due to self (vegetative) propagation and dispersal by floodwaters. It is probable that S. fragilis is propagated and dispersed in the same manner. Although aesthetically pleasing and having many beneficial qualities the alien willows also pose a potential threat to the conservation of indigenous riparian species and may alter the hydrology of the watercourses they invade.