Since we arrived on the planet, we've had a relationship with plants. We eat them, use them as building materials and tools, weave fabrics from them, craft musical instruments from them, create art from them, make cosmetics and medicines from them… Plants intertwine with our lives and contribute in a big way to our economy.
While our relationship with plants is ancient, the formal study of this field is relatively new. In 1986, American botanist John Harshburger coined the term ethnobotany. He used the term to describe "the study of the plants used by the primitive and aboriginal people." Others modified the definition so as to not suggest that some humans were more "primitive" than others and to broaden the uses. Most ethnobotanists study how people of a particular culture or region make use of indigenous plants.
Although scientific study had been ongoing for some time, botanist Richard Evans Schultes is considered the father of ethnobotany. Starting in the early 1940s this Harvard professor made multiple trips to the Amazon to study the use of plants by native people. He published nine books, the most popular is one he coauthored with chemist Albert Hofmann, The Plants of the Gods: Their Sacred, Healing, and Hallucinogenic Powers.
Canadian anthropologist Wade Davis was a student of Shultes. He wrote a book about Shultes' work in the Amazon called One River: Explorations and Discoveries in the Amazon Rain Forest and also published a photography book about Schultes entitled The Lost Amazon: The Photographic Journey of Richard Evans Schultes.
Not surprisingly, ethnobotanists have a strong background in botany beginning at the undergraduate level. The University of Hawaii is well known for offering B.S., M.S. and Ph.D. degrees in ethnobotany.
You may also wish to check out the Society for Economic Botany (SEB). According to their website, this international organization "was established in 1959 to foster and encourage scientific research, education, and related activities on the past, present, and future uses of plants, and the relationship between plants and people, and to make the results of such research available to the scientific community and the general public through meetings and publications." The SEB publishes the journal Economic Botany and an online newsletter.
Western Washington University in Bellingham, Washington, (north Seattle) also offers a program.
According to Boulder ethnobotanist Trish Flaster, director of Botanical Liaisons, "the most common jobs are academic positions and botanical gardens. However, ethnobotanists are also needed in public health and by herb companies and research and development companies. Ethnobotanists can also create their own niches in various locations, setting up pharmacies in medical offices, regulatory agencies, natural product organizations and nongovernment organizations." She adds that, while careers outside of academia and botanic gardens are not as secure, they can be rewarding. Flaster should know. She has traveled the world as an ethnobotanist and has consulted for a number of companies.