True lilies grow from bulbs, which are overdeveloped roots that store nutrients for next season's blooms. Transplanting lily bulbs should be easy if you understand the lily's pattern of growth, bloom and regeneration. The problem is that lily bulbs never really go dormant. They gather food all summer and early fall, develop root structure all fall and winter and begin growing as soon as they sense the sun warming the ground in spring. However, following a few guidelines will improve your chances of success.
Prepare planting holes about a foot deep and wide, 8 inches to a foot apart before you start to dig up your lilies if possible. Make holes a few inches deeper for oriental bulbs, which tend to be larger. Line each of the holes with a cushion of compost and peat moss.
Dig lily bulbs in late fall after all the foliage has died down. Dig a circle around the plant about 8 inches out from the main stem. Dig carefully---bulbs may have grown tissue in any direction from the stem.
Pry the bulb mass up from underneath gently with a garden fork, disturbing as few roots as possible. Gently rinse clumps of dirt off so you can see how many bulbs you have. Cut the stem off at the neck of the parent bulb and set it aside on a piece of newspaper.
Twist adult bulbs apart and dust the necks and any breaks with a plant fungicide powder, sold in garden centers. Inspect the bulbs for signs of rot or damage from rodents and discard damaged bulbs. Do not let lily bulbs dry out; if you must delay planting, wrap them in muslin or cheesecloth and keep them in a cool, moist place like a refrigerator vegetable crisper.
Place each lily bulb, roots down and neck up in a hole with its roots spread. Back fill with garden soil amended with compost and humus while holding the bulb 4 to 6 inches deep, depending on the size of the bulb. Water well and mulch with about an inch of well-rotted compost and leaves for winter protection.