Answer:
A greenhouse can be described as a place where plants are grown. In a greenhouse, the climatic conditions can be regulated according to the needs of a particular plant species hence making it possible to grow plants even when the season is not favourable for them.
Mendel, if alive, would have done his experiments in a greenhouse because the environment would be controlled there. Any outside factor would not disturb his plants under study. He would not have to wait for a particular season to carry out his studies.