The ecology of exotic herbaceous perennials grown in managed, native grassy vegetation in urban landscapes

This paper presents the results of a survey of species of exotic (non-native) herbaceous perennials naturalised in grassy swards in a range of garden and other sites in Britain. Information on site climate, productivity status and the management regime in operation are provided together with an assessment of the extent to which species are increasing, stable or decreasing. Key factors that underpin the establishment and persistence of vegetative propagules of exotic herbaceous perennials under these conditions are reviewed. An assessment is made of the threat the practice of cultivating these species in grassy swards in urban parks poses to British native plant communities. A preliminary assessment is made of the response of landscape professionals and the general public to both the idea of using exotic species in this way, and the visual characteristics of these vegetation types.