Generally, the water in the north is salty, and camellia likes acidic soil. Ferrous sulfate is mainly used to prevent camellia leaves from turning yellow. If your leaves are yellow, you can water them once with 5~7 ferrous sulfate, so the interval cannot be shortened. In fact, there is no proportion. You just need to put less. Too much is not good for camellia. Pour more water and less ferrous sulfate. If your leaves are not yellow, you can water them once every half month. I am. I'll tell you a little way. If there is no ferrous sulfate, you can add water with vinegar at home without too much. Pour it once every half month. No problem. I don't know if the ferrous sulfate tablets that everyone eats are ok. You can go to the flower market to buy a pack of ferrous sulfate, which seems to be two yuan a small bag.