Tell me, how many centimeters of land do you need in a greenhouse? Planned to plant lemon, oleander, hibiscus, hydrangea, azaleas.
Everything is very simple, read about the planned plants. About each individually. Everyone has a different root system. Maybe someone vertically, while someone grows horizontally. Take the maximum depth. This will be the answer to your question. Nobody will do this for you))) Do not forget about acidity. Hydrangeas and Azaleas, in my opinion, acidic soil is needed. I don’t know about others.