[header] How to divide and transplant lilies [title] Examine lilies each year to know when they need dividing. [step] Lilies need to be divided if they show an abundance of short and spindly stems. [title] Separate lilies in the fall , 3 to 4 weeks after flowering is completed. 
[step] You can harm the bulbs and roots if you separate lilies prior to flowering. [title] Use a garden fork to dig under and around lily clumps.