Harold Roth is a leading authority on plant and herbal magic. His book, The Witching Herbs, is an in-depth exploration of 13 essential plants and herbs most closely associated with witchcraft --13 because it's the witching number and reflects the 13 months of the lunar calendar. The plants are poppy, clary sage, yarrow, rue, hyssop, vervain, mugwort, wormwood, datura, wild tobacco, henbane, belladonna, and mandrake.