You need to drink water every day and water your plant at the same time. Then the plant's level will slowly increase! Your plant needs to be Level 4 (Lv.4) to be placed into the greenhouse and start producing seeds!
Once your plant has reached Lv.4:
1. Tap the plant
2. Select Move to greenhouse
and just like that the plant will be moved to the greenhouse!
＊Reminder 1: Once your plant is in the greenhouse, you will not be able to change its pot!
＊Reminder 2: You can just Swipe up in the main page to see your greenhouses!