The entry of the United States into World War II saw Schultes diverted to the search for wild disease-resistant Hevea rubber species in an effort to free the United States from dependence on Southeast Asian rubber plantations which had become unavailable owing to Japanese occupation.
Schultes became curator of Harvard's Oakes Ames Orchid Herbarium in 1953, curator of Economic Botany in 1958, and professor of biology in 1970.