Perennials For American Gardens: the Definitive A-Z Refereence Guide to Over 3000 Species, Cultivars, and Hybrids For Gardeners Across the Country by Ruth Rogers Clausen and Nicholas H. Ekstrom (Random House 1989)(635+/-). This is one of my favorite gardening books. It's truly encyclopedic in scope. My rating: 7/10, finished 2001.