Identification of South American tussock weeds
Neville Walsh, National Herbarium of Victoria, Birdwood Avenue, South Yarra, Victoria 3141, Australia.
Of the 400-odd species of grass in Victoria, 180 are introduced (Ross 1996). By far the greatest majority of these are from Mediterranean countries and the Cape region of South Africa. This is due to the similarity of climates and soils to those found in Victoria, and that these areas were the principal source of agricultural crops and settlers in this State. The proportions of exotic versus native species of grass are similar for other States, but the exact figures are difficult to ascertain.
Only 17 species of naturalized grass in Victoria originate from South America (Walsh 1994). Of these, several species, although weedy, are currently of little consequence to bushland or cropland (e.g. perennial species of Bromus, Panicum racemosum, Paspalum quadrifarium, P. urvillei). Other species (e.g. buffalo grass, Stenotaphrum secundatum) are generally regarded as useful and rarely escape into bushland, leaving a few species that are regarded as seriously invasive of natural or created plant communities. These are species of Paspalum (common paspalum, P. dilatatum and water couch, P. distichum) the pampas grasses (Cortaderia jubata and C. selloana), the tussock-forming species of Nassella (N. charruana, N. hyalina, N. leucotricha, N. neesiana and N. trichotoma), Achnatherum caudatum (formerly Stipa caudata), and to a lesser degree Piptochaetium montevidense.
Interestingly, it is only in the past few decades that Cortaderia, like Nassella and Achnatherum, has been identified as having a strongly weedy tendency, with an apparently rapid extension of range in the past few years.
Plant Protection Quarterly (1998) 13 (2) 59-62.