As a primary source from 1852--a Scottish botanist encountering Chinese garden practice and plants--this is first rate. The politics behind it are difficult to comes to terms with, though. Fortune was in China intermittently for more than 9 years mostly in the capacity to steal native Chinese tea plants, tea processing information, and tea growing experts and export them to to British-controlled India, where tea would be propagated for the empire in quality and quantities never before known.
Fortune's descriptions of flowers and gardens and Chinese customs are useful, but beware the imperialist gaze!