Legumes in temperate Australia: A survey of naturalisation and impact in natural ecosystems

Some of the most damaging weeds of natural ecosystems in temperate Australia and similar Mediterranean environments are legumes. A study was undertaken to determine the level of naturalisation and impact of exotic legumes in temperate Australia. This was the first step in attempting to develop a method of evaluating the weed risk of future legume species introductions. A study of nursery catalogues indicated that legumes were widely cultivated throughout temperate Australia in the early part of the 20th century. A number of these species were able to escape from cultivation and have become part of the region's naturalised flora. Non-climbing herbaceous legume species were the most common type of legume recorded as naturalised. A smaller number of naturalised species were reported as being present in natural ecosystems. A higher introduction pressure increased the chance of legume species being able to naturalise and also establish in natural ecosystems. The results of a questionnaire showed that of the legume species that established in natural ecosystems there were differences in regard to their perceived level of impact. Woody perennial legumes had the highest reported impacts and non-climbing herbaceous species the lowest. The higher impact species also had a history of use as garden ornamentals, while lower impact species were largely agricultural. The results of this survey suggest that until greater accuracy is achieved with regard to the prediction of weeds and their impact, a precautionary approach should be taken to the importation, sale and cultivation of woody legume species.