As a young botanist from the Duchy of Holstein, he started his career as a pupil of Johan Christian Fabricius at Kiel and Heinrich Adolf Schrader at the University of Göttingen.
[1] In 1803 he obtained his doctorate from the University of Kiel with the dissertation Observationes Botanicae quibus plantarum cryptogamarum ordines.
In the summer of 1803, with Weber, he toured southern Sweden and made the acquaintance of Erik Acharius, Olof Swartz, Carl Peter Thunberg and Adam Afzelius.
As a result of the journey, Mohr and Weber published Naturhistorische Reise durch einen Theil Schwedens (1804).
[3] In addition to the aforementioned work, he also published with Weber the following: In 1806 Olof Swartz named the botanical genus Mohria after him.