Where do you live? If you live where all of your deciduous trees lose their leaves, your elm will eventually lose its leave also. Do you have consistant temps. below 45F? If so, then your tree will lose its leaves. If you live in a sub-tropical area that gets chilly but doesn't freeze often, it may lose only a few leaves and then lose all of last years leaves as spring causes new leaves to push the old ones off. If that is the case, i'd leave it outside