I'd definately recommend doing what I always do - before ingesting (or inhaling the smoke from) any herbs on the recommendation of a single author, do thorough research in a good medicinal herbals first.
Always a good idea - I check in several medicinal herbals when I'm just looking for the medicinal properties. they all generally agree on part, but one will say if it's not good in cases of hypertension, and another if it isn't good if you're pregnant, etc.....