Some of these books are pretty old, but these include classics (e.g. Fernald, Gleason, Esau) and the others are helpful in one way or another. While the plants haven't changed much since these books were published, some new ideas have evolved and you might find plants that have been shifted to a different taxa, (e.g. poison ivy was once classified with the sumacs as Rhus radicans and is now classified with poison sumac and poison oak in the genus Toxicodendron). Search one of the databases on the "Links Page" or Wikipedia search to check on these taxonomic migrations.

The links provided take you to or a specialized publisher such as Bur Oak Books where you can find out more about availability and also find new publications dealing with these same topics. If you can't find what you want on, try Barnes and Noble.