Contemporary fragments from newspapers and books around the time of Gregor J. Mendel’s famous experiments and lectures in Brno (Brünn) provide new evidence on the early beginnings of his experiments and experimental design. The fragments show that his early efforts were strongly focussed on plant breeding of varieties and at the time particularly discussed in the context of acclimatization experiments. Further newly found sources highlight that Mendel’s 22 pea varieties might have been already presented to the public at exhibitions at the early beginning of his experiments in 1855. While Mendel was convinced that those experiments had economical relevance, contemporaries anonymously expressed doubts on this point. Criticism on his analysis in Brno also continued after the conclusion and presentation of his experiments. Johann Nepomuk Bayer (1802–1870), a railway expeditor and botanist for example doubted Mendel’s concept of dominant and recessive traits and published a sharp comment in his final book on results of his own field trip. This previously unknown early citation of Mendel’s article from 1866 is a particular oddity in the history of Genetics, because there is a huge likelihood that it might be a missing link in the early citation network of Mendel’s work in the 19th century that eventually ensured that it could be rediscovered in 1900. The citation though also raises the question if this remark was only the tip of the iceberg in a longer and continuing discourse between the two researchers.