[5] After earning a Bachelor of Science in 1969 from Tufts,[6] Semple enrolled at Washington University in St. Louis, spending most of his time at the Missouri Botanical Garden.
[6] His 1972 PhD dissertation was entitled The Cytology, Flavonoid Chemistry and Systematics of the Texas Sleepy Daisy Xanthisma texanum DC.
[1] Semple acquired a background in cytotaxonomy and evolutionary classification while performing this research, as well as an affinity toward the study of flowering plants in the family Asteraceae.
[5] For post-doctoral studies, Semple remained at Washington University in St. Louis, also serving as a lecturer and visiting assistant professor, into the summer of 1974.
[9] In February 2021, he and botanist James B. Beck published a revision of the genus based on a large phylogenomic study.