Hi, if the stalks are turning brown you can go ahead and take them out of the pot and divide them. The smaller bulblets need to be planted only a couple of inches deep, but the mature bulbs need to be planted about 6 inches deep. If the leaves are still green, leave them be until you see that they are turning brown. I sometimes dig up some of my lillies even when they are still somewhat green and divide them and they seem to come back just fine the next year. As long as the bulb is not damaged they should recover quickly. Hope this helps!!