In 1952, he joined the Hebrew University faculty, lecturing in botany. From 1952 to 1953, he was a research fellow at the University of Cambridge and in 1956 at Harvard University. He became an associate professor at the Hebrew University in 1960 and a full professor in 1965, serving dean of the faculty from 1964 to 1966 and pro-rector from 1969 to 1970.