Restoring American Gardens: An Encyclopedia of Heirloom Ornamental Plants, 1640-1940
http://www.amazon.com/Restoring-American-Gardens-Encyclopedia-Ornamental/dp/0881926191/ref=sr_1_1/103-3656053-0164658?ie=UTF8&s=books&qid=1176064032&sr=8-1

For Every House a Garden: A Guide for Reproducing Period Gardens
http://www.amazon.com/Every-House-Garden-Reproducing-Gardens/dp/0874515149/ref=pd_bxgy_b_img_b/103-3656053-0164658?ie=UTF8&qid=1176064032&sr=8-1

Landscapes and Gardens for Historic Buildings: A Handbook for Reproducing and Creating Authentic Landscape Settings: A Handbook for Reproducing and Creating ... for State and Local History Book Series)
http://www.amazon.com/Landscapes-Gardens-Historic-Buildings-Reproducing/dp/0761989307/ref=pd_sim_b_2/103-3656053-0164658?ie=UTF8&qid=1176064032&sr=8-1

And etc. There are literally dozens on Amazon and probably at your local library, too.