Answer: The absolute best time would be after the lilies have bloomed and the foliage has browned and withered. Depending on the variety of oriental lilies you have they may have bloomed and died down by then, but I seriously doubt it - most bloom July through August. In an absolute emergency, rather than have them destroyed, you could try moving them now (if your ground isn't frozen) before they have put out spring growth. This is not an ideal scenario, but, sometimes they are tougher than we think. Be sure to baby them a bit after "offending" them in this matter. Enhance their new site with organic matter (compost, leaf mould, etc.). Also, assure they have adequate water and good drainage.
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