Joseph Gaertner (12 March 1732 – 14 July 1791) was a German botanist, best known for his work on seeds, De Fructibus et Seminibus Plantarum (1788-1792).

Some of F2 plants had entirely new traits but he was unable to give possible explanation for observed data but which was brilliantly done by Mendel Julius Sachs writes "[H]e gives us the impression of a modern man of science more than any other botanist of the 18th century, with the exception of Koelreuter.

He knew how to communicate with clearness of language and perspicuity of arrangement whatever he gathered of general importance from each investigation.... [H]is great work was at once an inexhaustible mine of single well-ascertained facts, and a guide to the morphology of the organs of fructification and to its application to systematic botany.

"[1]By 1770, he had already begun work on his De Fructibus et Seminibus Plantarum, but thereafter he gave himself up almost entirely to it, becoming nearly blind through his persistent studies, partly with the microscope.

[1] The work's minutely accurate descriptions, comprising a thousand and more species, introduced a new era in plant morphology.