lilies are tough as nails, outside will work fine. work in a tablespoon of 4-10-10 organic bulb food for every bulb in the pot, add a half cup of bone meal to the soil surface as soon as the eyes appear. when they're done flowering give them another tablespoon of 4-10-10 per bulb, followed up by a cup of alfalfa meal in august. your bulbs will be twice the size next spring!