Part of the work I do is educating folks on folk medicines and how they work. It may come as a surprise to many people but plants contain chemicals, and these chemicals, much like pharmaceutical medications, require certain cautions when it comes to use.  You should never use any plant without consulting a knowledgeable herbalist or researcher. If you yourself are a practitioner, than there are certain resources I think are necessary to insure the safety and health of your patients. Here are some great reference books for herbal constituents and interactions:

“Herbal Contraindications and Drug Interactions” Francis Brinker

“MAD Oilers Guide to Essential Oils and Drug Interactions” Michael J. Ivey R.N.

“PDR for Herbal Medicines, 4th Edition”

“American Herbal Products Association’s Botanical Safety Handbook, Second Edition”

“Herbal Vade Mecum: 800 Herbs, Spices, Essential Oils, Lipids, Etc.-Constituents, Properties, Uses, and Caution” Gazmend Skenderi

“The Constituents of Medicinal Plants: An Introduction to the Chemistry and Therapeutics of Herbal Medicine” Andrew Pengelly

Also invest in some identification books if you’re going to be wild harvesting anything. I personally like the Falcon guides. They have large photos and a lot of good information. Peterson and Falcon both make great guides for North American medicinal plants. It’s also valuable to learn some plant taxonomy if you’re going to be identifying anything. Here are some good taxonomy books:

“Plant Identification Terminology: An Illustrated Glossary” by James G. Harris and Melinda Woolf Harris

“Botany in a Day: The Patterns Method of Plant Identification” by Thomas J. Elpel

“Plant Taxonomy: Past, present, and future” by Rajni Gupta

I will say a few of these (the PDR especially) are a little on the expensive side but they are important resources for anyone who is giving out remedies or plant knowledge.

Some will say that knowledge passed down from an expert herbalist is enough, I’m here to tell you that it’s not. You need to know drug interactions more than anything. We’re living in a time when nearly everyone is taking some kind of medicine, whether over the counter or prescription, and these chemical compounds absolutely interact with herbals, sometimes in a very dangerous way e.g. St. John’s Wort which has dangerous interactions with antidepressants, amphetamines, blood thinners, and analgesics for a start. Know your craft! Don’t assume that just because it comes from the wild it’s safer than a prescription medication.