Plants For A Future
An online resource center for rare and unusual plants, particularly those which have edible, medicinal or other uses. According to their website, they practice vegan-organic permaculture with emphasis on creating an ecologically sustainable environment based largely on perennial plants. Their database includes over 7,000 plants.
www.pfaf.org

Example Plant Lists & Water-Requirement Calculations for Tucson
Click to download: Appendix 4: Example Plant Lists & Water-Requirement Calculations for Tucson, Arizona (128k PDF)