Gregor Mendel studied seven distinct pea plant traits in his experiments.
Between 1856 and 1863, Mendel cultivated and cross-pollinated garden peas in the monastery garden at Brno. He selected traits with clearly contrasting forms, such as round versus wrinkled seeds and tall versus dwarf plants, making the inherited differences easier to count across generations.
The seven traits were seed shape, seed color, flower color, flower position, pod shape, pod color, and plant height. By tracking these traits mathematically, Mendel showed that inheritance followed predictable patterns rather than blending permanently from one generation to the next.
A common mix-up is to count the two forms of each trait separately. Mendel studied seven trait pairs, not fourteen traits: for example, yellow and green were the two alternatives for one seed-color trait. His 1866 paper helped establish the foundations of modern genetics, although scientists initially paid little attention to it.