Soon after graduation, Flor was selected for a newly created post in
natural history at Christiania Cathedral School (now the
Oslo Cathedral School), becoming Norway’s first dedicated natural‑science teacher. He later taught at the
Military Academy, helped establish the
Christiania Burgher School and conducted popular
Sunday school classes. A staunch advocate of hands‑on learning, he led numerous botanical excursions—often held on Sundays—much to the displeasure of some colleagues and
ecclesiastical authorities. In 1806 Flor took charge of the Paléhagen garden at
Bjørvika, bequeathed to the school by chamberlain
Bernt Anker, and maintained it as Norway's first public botanical garden (and the country’s first school garden) until the state assumed control in 1815. Throughout this period he collaborated with friends such as
Christen Smith and
Jens Wilken Hornemann, sowing some 258 species in 1813 alone. In April 1813 he received from forest‑inspector Nicolai Hersleb Ramm a detailed account of Norway’s first known
lithopedion (a ten‑year 'stone baby') from
Kvikne, which Flor preserved in his papers. In 1817 Flor issued two
floras:
Systematisk Characteristik, a detailed local flora for pupils of the Cathedral School, and
Ledetraad for Begyndere, a more widely aimed determination flora that incorporated
Linnaean taxonomy as an integral framework. The following year he published , which treated the
medicinal plants of Class XXIV in Linnaeus's system and stands as Norway's first student text on medical botany. These works drew heavily on sources such as
Frederik Christian Kielsen's Danish‑area flora, the later volumes of
Flora Danica,
Johan Wilhelm Palmstruch and
Olof Swartz's
Svensk botanik, and
Christian Schkuhr's
Riedgräsern. ==Death and legacy==