What is a weed? Definitions abound, some more clever than true. For the author, weeds are plants that grow uninvited in places disturbed by people or their animals. But although weeds may invade our fields and gardens, most are not aggressive away from disturbed areas. Some have notable virtues, whether medicinal, culinary, or even ornamental. Not intended to be a manual of weed identification --- although the descriptions, drawings, and photographs will help readers name many of their newfound friends --- or weed eradication, this book is for anyone interested in weeds as plants. A veritable natural history of weeds, it will encourage readers to look anew at these previously unwelcome guests.