Harold St. John (July 24/25 1892 – December 12, 1991) was a professor of botany at the University of Hawaiʻi at Mānoa from 1929 to 1958.
[1] The St. John Plant Science Laboratory building on the Mānoa campus, which houses the botany department, is named after him.
[2] Not long after his arrival in Hawaii, he joined the Bernice P. Bishop Museum's Mangarevan Expedition of 1934, which returned with perhaps the richest collection of Polynesian plants ever made.
[3] During World War II he took a leave of absence to lead a scientific team to the rainforests of Colombia in search of Cinchona trees in order to provide additional sources of the malaria drug quinine, which was in short supply.
After the war he investigated the effects of radiation on vegetation in the Marshall Islands for the United States Atomic Energy Commission.