This edition includes treatments of many newly described or discovered taxa and recently introduced plants, and it reflects major improvements in plant taxonomy. Nearly two-thirds of the 7,600 species, subspecies, and varieties that 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. The second edition also allows for identification of 240 alien taxa that are not fully naturalized and features a new chapter on geologic, climatic, and vegetation history of California.