I studied botany before I studied medicine, having had the good fortune to pursue an undergraduate degree under the direction of the late Dr. Richard Evans Schultes, longtime director of the Harvard Botanical Museum and god-father of modern ethnobotany. Schultes was an expert on psychoactive and toxic plants, especially of the New World tropics. Initially, through his stories of the indigenous lifestyle of Amazonian peoples, and later by helping me undertake fieldwork in this region, he awoke in me a keen interest in the botany of useful plants that led me to become first an investigator and later a practitioner of botanical medicine.

When I moved on to Harvard Medical School, I was dismayed to find that none of my teachers, even of pharmacology, had firsthand knowledge of the plant sources of drugs. Since then I have been continually struck by the lack of awareness of the medicinal and toxic properties of plants in our culture. Examples are unfounded fears of poisoning by common ornamentals such as the poinsettia, exaggerated fears of herbal remedies such as Chinese ephedra, ignorance of the vast medicinal importance of such spices as turmeric and ginger, and lack of awareness of the toxic and psychoactive properties of other spices, for example, nutmeg and mace.

At the root of this problem is the distance that exists between plant scientists and health scientists. Because I am trained in both worlds, I have been very conscious of it all my professional life. This intellectual gap creates difficulties for botanists who want to learn the medical significance of plants with pharmacological effects and for physicians, nurses, and pharmacists who want to learn how plants influence health, whether for good or ill.

By bringing together specialists from both sides of this divide, the present book does a great service. It gives different perspectives on poisonous and injurious plants while remaining grounded in the integrative science of modern ethnobotany. I wish it had been available when I was first practicing medicine and, because of my background in botany, was often asked questions about the harmful potentials of plants and products derived from them.

I meet many people who imagine that most wild plants are dangerous, who think that if you pick and eat plants at random in the backyard or woods you will die. In fact, the percentage of plants that are really harmful is quite small, as is the percentage that is really beneficial. If you wish to get to know plants, a good place to start is to learn about those that can kill or cause serious harm. This handbook will be an invaluable resource in that educational process.