last summer I planted some already bloomed oriental lilies. I have no idea how to make them continue blooming for future years. Am I supposed to cut the heads off. I read mostly to just pull off the spent blooms and to leave the stalk and foliage to die down naturally. But I've also read to pull the stalk out of the bulb and to let the bulb re-bloom. Which is correct, or neither. I want my lilies to last but have no idea how to care for them so that they will re-blosom. Thanks in advance to anyone who can help!