I found this neat book called "Amish Folk Remedies for Plain and Fancy Ailments" by William R. McGrath. Which, according the publisher, is "a collection of historic Amish folk remedies." It was published by S. Chupp's Books in Burr Oak, Mich., first in 1984 and this copy is its sixth printing.
It has a bunch of recipes for health ailments, making salves, etc. using plants and herbs.