With this in mind, I omitted such taxa as Ageratina aromatica (small-leaved white snakeroot), the ditch-loving Coreopsis nudata, Helenium vernale (spring helenium), and on and on.
On what plants to include: the dilemma was not what plants to include in this book, but which to omit. Wonderful native plants are mentioned by botanists, native enthusiasts, and conservationists, but many are so difficult to find that I did not include them. Availability to mainstream gardeners became one of the main criteria for both inclusion and omission, based on my research for each genus. With this in mind, I omitted such taxa as Ageratina aromatica (small-leaved white snakeroot), the ditch-loving Coreopsis nudata, Helenium vernale (spring helenium), and on and on. Other plants begged to be included, but I couldn't find anyone selling them. Another criterion was potential for the future. Perhaps, with the native plant movement continuing to gain momentum, I can include many more in the next edition.