The second edition of The Jepson Manual thoroughly updates this acclaimed work, the single most comprehensive resource on California's amazingly diverse flora. The Jepson Manual, second edition, integrates the latest science with the results of intensive fieldwork, institutional collaboration, and efforts of hundreds of contributing authors into an essential reference on California's native and naturalized vascular plants. The second edition includes treatments of many newly described or discovered taxa and recently introduced plants, and reflects major improvements to plant taxonomy from phylogenetic studies. Nearly two-thirds of the 7,600 species, subspecies, and varieties the volume describes are now illustrated with diagnostic drawings. Geographic distributions, elevation ranges, flowering times, nomenclature, and the status of non-natives and native taxa of special concern have all been updated throughout. This edition also allows for identification of 240 alien taxa that are not fully naturalized but sometimes encountered. A new chapter on geologic, climatic, and vegetation history of California is also featured.