Career
He was a lecturer at the University of Copenhagen Botanical Garden from 1801. After the death of Martin Vahl in 1804, the task of publishing the Flora Danica was given to Hornemann, who subsequently issued fasc. 22-39 (1801–1840) with a total of 1080 plates.
J.W. Hornemann was professor of botany at the University of Copenhagen from 1808 and director of the Botanic Garden (from 1817).
Hans Christian Andersen was a frequent visitor in Hornemann"s home in Copenhagen. Andersen used him as model for "the Professor of Botany", who understands the gestures of the flowers, in the tale "Little Ida"s Flowers".