Rupert Barneby was born in Monmouthshire, England. He attended Cambridge University where he received his B.A. in History and Modern Languages in 1932. He came to the United States in 1937 and established permanent residency in 1941.
Barneby's association with The New York Botanical Garden spanned nearly a half century. He arrived as a visiting scholar in the 1950s and shortly thereafter accepted a staff position as Honorary Curator of Western Botany. He went on to become a Research Associate and an Editorial Consultant for Brittonia, the Garden's esteemed scientific journal covering systematic botany.
A self-taught botanist, Barneby rose to become a world expert in Leguminosae (the bean family) and Menispermaceae (the moonseed family). He spent his career at the Garden curating and studying the world's best collection of New World Leguminosae. In 1978, he was awarded an honorary Doctorate of Science degree from The City University of New York.
In 1980, he was the winner of the Henry Allan Gleason Award, an annual award from The New York Botanical Garden for an outstanding recent publication in the field of plant taxonomy, plant ecology, or plant geography. In 1989, the American Society of Plant Taxonomists awarded Barneby with the Asa Gray Award for his contributions to systematic botany. In 1991, The Garden honored Barneby by institutionalizing his legacy through the establishment of the Rupert C. Barneby Fund for Research in Legume Systematics. The Engler Silver Medal, botanical science's highest honor for publications, was awarded to Barneby in 1992 for his monographic work Sensitivae Censitae: A Revision of the Genus Mimosa Linnaeus (Mimosaceae) in the New World.
Barneby was known for his talent for discovering or rediscovering rare and local species. In the course of his five decades of research, Barneby described and named over 1,100 different plant species new to science. A botanist is fortunate to have a new species of plant named in his honor. Barneby had not only 25 different species named after him, but also, four genera (groups of species sharing common characteristics, such as roses or oaks) of plants' Barnebya, Barnebyella, Barnebydendron, and Rupertia.
Barneby was a member of the American Society of Plant Taxonomists, the International Association for Plant Taxonomy, and the New England Botanical Club, and a Fellow of the California Academy of Sciences. He is the Curator Emeritus in The New York Botanical Garden's Institute of Systematic Botany, and 1999 recipient of the International Botanical Congress' Millennium Botany Award for a lifetime of contribution to science.
He and his partner Dwight Ripley had a relationship which lasted 50 years together.