This book is about plants that have been introduced to new areas, usually new continents. It is about the attempts that have been made to characterize which introduced species will become serious weeds, about their impacts on native communities, and on how introduced weeds might be controlled. Studies of invasive plants have provided a rich literature in applied plant ecology. The invasion of plants into a new environment is an example of succession in action and an experiment on the role of species in communities. In the following chapters we bring together theory and application to focus on both what the study of introduced plants reveals about ecological processes and what ecological processes might be applied to management programs. We consider how community and population ecology can be brought to bear on the topic of invasive plants. Because many introduced plants become invasive and are considered to be weeds, we start here by defining weeds. Next, in this introductory chapter, we describe the socio-economic context surrounding introduced plants and introduce topics to be discussed in more detail in following chapters.

Weeds and the value of native species

Weeds are plants growing out of place or plants whose value has not yet been discovered. They have demanded the time, attention and resources of farmers, gardeners and proud homeowners for centuries. Despite being pulled, sprayed, cursed and competed with, in the long run the weeds always seem to come back.