If an item won't fit in your garden it will automatically be bubbled until you have space to place it.
This is not designed to be a long-term solution for storing items but we know that some players like to do this.
The maximum amount of bubbles that the game supports is 500 and before you reach that number you will see a warning pop-up to let you know. While 500 is the max limit which the game will allow to appear in your garden, even a smaller number of bubbles floating around may cause performance issues such as lag or freezes. Please try keeping the number of bubbles in your garden to a minimum!