One of the best investments you could ever make is Dr. Christopher's "School of Natural Healing" book - even though his children have altered/added a bit, ALL the information about how to grow, harvest and make herbal preparations seems to be intact. If you could find one published before 1983, that'd be awesome, but if not, the 25th Anniversary edition (even though it's edited) is worth it's weight in platinum!
Wishing you the best of luck in your search.
Water