In which generation were recessive traits visible in a few plants in Mendel and experiments?

In Mendel's experiments, recessive traits became visible in the F2 generation. Initially, in the F1 generation, only dominant traits were expressed, but when the F1 plants were self-fertilized, the recessive traits reappeared in approximately 25% of the offspring in the F2 generation. This observation led Mendel to formulate his principles of inheritance.