Answer: Container citrus are generally grafted onto a dwarfing rootstock to help keep them at a manageable size. They can also be pruned later on if needed.
It will need to be brought indoors, yes. A half whiskey barrel sized container is usually sufficient, the plant is grown permanently in its container and never planted in the ground. It is usually moved on a dolly -- it is very heavy.
Here is general information on caring for container citrus that you may find helpful. You may need to cut and paste the complete url into your browser to make it work correctly.
Enjoy your tree!
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