Gregor Mendel

Gregor Mendel begins his controlled pea-crossing experiments

Before making the famous crosses, Mendel spent two growing seasons checking whether dozens of pea varieties bred true.

Spring 1856, a monastery garden in Brünn

In the spring of 1856, Gregor Mendel began the garden-pea hybridization series he later described in Experiments on Plant Hybridization, at the Augustinian monastery in Brünn — now Brno.

It followed two years of preliminary testing. He had obtained 34 pea varieties from seed suppliers and kept the 22 that bred consistently.

Tweezers, and flowers that stay shut

To control parentage, Mendel opened an immature flower bud, removed its stamens with tweezers, and applied pollen from the chosen second variety to the stigma.

Peas suited the design: stable contrasting forms, short generations, fertile hybrids, and flowers that normally self-pollinate before opening. Earlier artificial fertilizations of ornamental plants had shown him that the same hybrid forms recurred with striking regularity.

The results were still eight seasons away

No laws were announced that year. Mendel ran the crossings through 1863 — eight years, as he described the series in a later letter — and his paper records more than 10,000 plants closely examined.

He did not begin with seven genes. He chose seven pairs of readily distinguishable plant characteristics, and his 1866 paper uses dominant and recessive but none of the later vocabulary of genes, alleles, genotype or phenotype.

The often-repeated total of about 28,000 plants is not a figure Mendel's paper gives; the text counts plants, seeds and observations separately.

Sources

Researched 23 Aug 2026 7 sources 2 audit passes, 1 issue open

How this was checked

Researched from the web into a fact sheet, rewritten from that sheet, then audited against it by a different model. How the pipeline works →

What the sources leave uncertain

No single opening day is documented. A later letter to Carl Nägeli identifies the pea experiments as running from 1856 through 1863, while scholarly reconstruction places the first crossings in spring 1856.
If 'research' includes Mendel's preliminary varietal trials, it began about two years earlier. The year 1856 marks the start of the principal crossing series, not his first botanical investigation.
The frequently repeated total of approximately 28,000 plants is not stated as such in Mendel's paper; the primary text separately counts plants, seeds, and experimental observations.