Harriet Barclay obtained her Ph.D. in 1928 from the University of Chicago under the direction of the pioneer ecologist Dr. Henry C. Cowles. She and husband Dr. Bertram Donald (Don) Barclay soon joined the faculty at the University of Tulsa.

In 1953 Don was killed in an automobile accident, and Harriet assumed his position as chair of the Botany Department with full-time teaching responsibilities. She retired from TU in 1972 and continued teaching at North Carolina State University, the University of Oklahoma Biological Station and Rocky Mountain Biological Laboratory.

Among Harriet's many contributions to Oklahoma and the Tulsa community were her involvement in the early stages of a roadside wildflower program, establishment of Redbud Valley Nature Preserve (now with its Harriet G. Barclay Nature Center) near Catoosa, years of dedication to the Tulsa Garden Clubs as well as her leadership in ONPS.