Question
I'm looking for the ultimte authority on choosing and caring for perennials.  I'm gardening in Spofford, New Hampshire.  Thank you for you consideration of my question.

Answer
Hi Christine.

For my money, I'll take just about anything by the American Horticultural Society. I rely heavily on the _American Horticultural Society A-Z Encyclopedia of Garden Plants_, but this includes trees, shrubs, and annuals. _American Horticultural Society Encyclopedia of Plants and Flowers: The Definitive Practical Guide_ would be a good bet for you. It is not perennials exclusively, but covers them in full with discussion of pests and diseases. It's an enormous book. My favorite element is *all* the photos. AHS also has a really small book on just perennials. _American Horticultural Society Practical Guides: Perennials_. I haven't looked at this one, but you might want to check it out.

Hope this helps. Good luck with your garden!