ABSTRACT
Urban areas are highly dynamic plant habitats. Within towns and cities there are always some patches undergoing change, whether being cleared for new development, being abandoned because the company owning the land has gone out of business, becoming covered by brambles, receiving illegally dumped waste most nights, or having its flower beds replanted with annual flowering species. In some cases natural recolonization is at work, in others, human actions are determining the development trajectory of a novel ecosystem. Such a complexity of influences helps, in part, to explain the fascination of ecology in cities, whether of particular trees and their survival and decline or of invasive species such as London's parakeets or the Japanese knotweed. Environmental factors influencing the urban flora include the urban heat island effect. Their successes and failures colour the lives of townspeople and city folk. Drought-, salt-and erosion-resistant tamarisk shrubs, were originally introduced into the United States as ornamental species for people's gardens.
