Traditionally, the task of increasing crop productivity has been seen as the role of crop breeders and agronomists, drawing respectively upon the sciences of plant genetics and plant physiology. From an agricultural science point of view, weeds of crops have been seen simply as a nuisance to be removed using the best available technology to hand. Much of weed science has therefore been devoted to the provision of ‘tools’ for weed removal. Only in relatively recent times has weed management been viewed as a problem to which ecological principles can be applied.

For historical reasons, then, the study of weeds has been divided between two groups of scientists. Agronomists and horticulturalists have seen the presence of weeds as a pragmatic problem to be solved (how can the weeds be killed?). Plant ecologists, on the other hand, have seen cropped land as somewhat unnatural, human-managed habitats and weeds as particular organisms that are able to exploit such habitats (i.e. as academic curiosities). Books considering weeds have followed this dichotomy, although there has been more emphasis on the practice of weed control than on weed ecology. Indeed, despite the fact that much of the temperate regions and an increasing area of the tropical regions of the world are farmed or managed in some way, it is surprising that plant ecologists have given agroecosystems relatively so little attention. As with other areas of pest control, the agroecosystem–natural ecosystem dichotomy has persisted to the detriment of weed science. However, with increasing concern over the preservation of biodiversity, many ecologists are becoming interested in alien invasions threatening more natural habitats (‘environmental weeds’).