Afterwards he was successor to Julius Sachs (1832–1897) as professor of botany at the Agricultural Academy of Poppelsdorf in Bonn, a position he maintained until 1898.
After his military service, Klebs became an assistant to Julius Sachs at the University of Würzburg and Wilhelm Pfeffer at the University of Tübingen.
He enthusiastically took part in W.F.R. Suringar's classes and excursions, but was mostly drawn to the experimental botany outlined in Julius Sachs' 'Lehrbuch der Botanik' from 1868.
His principal works are an English edition of Sachs Text-Book of Botany (1875), editions of the Flora Capensis and of the Flora of Tropical Africa, and Index Kewensis (1905).
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