[9] From 1974 to 1975 he lived in Costa Rica and helped build the Wilson Botanical Garden at the Las Cruces Biological Station.

He has done research and taught university courses in "ethnobotany and ethnomedicine, phytochemistry, floristics and conservation biology.

He is also the author, co-author, editor, or co-editor of thirty books and monographs, varied among scientific and general interest.

[1] He has been a co-collector with more than two dozen botanists, including Brian M. Boom, Andrew J. Henderson, and Ghillean Prance.

In 2018 he received the David Fairchild Medal for Plant Exploration of the National Tropical Botanical Garden and in 2020 the H. Marc Cathey Award for outstanding scientific research that has enriched horticulture and plant science from the American Horticultural Society.