This updated edition includes new discoveries. Since the publication of the first edition of "Smart-Weeds to Hazelnuts" in 1987, thirteen additional species and one hybrid have been discovered in Illinois. In addition, numerous nomenclatural changes have occurred for plants already known. This second edition updates the status of the Polygonaceae, Hamamelidaceae, Platanaceae, Fagaceae, Betulaceae, and Corylaceae in Illinois. Each of the newly discovered species has been added and is fully illustrated. Updated nomenclature as well as Illinois distributional data are included for each species. In addition to the fourteen new plant illustrations, the appendix contains new information on the descriptions and the geographical locations of plants in the first edition, and revised identification keys. Robert H. Mohlenbrock and Paul M. Thomson Jr. have included a complete description, illustrations showing diagnostic features, distribution maps, and ecological notes for each plant included in this volume. This new edition will be invaluable to scholars of botany as well as laypersons interested in observing plants in their natural habitat.