Asiatic lilies are beautiful large flowers available in many colors including white, pink and red. They are bulbous plants that self propagate. While Asiatic bulbs are hardy and should be left in the ground through the winter months, they will need to be dug up and divided every few years as the garden becomes overcrowded and the plants bloom less than they did in previous years.
Wait until the bulbs become dormant to dig them up, which happens after the foliage turns yellow in the fall. At this time, digging them up will be less stressful on the bulbs and will give them a chance to take root during the winter months in their new location.
Cut back the yellow foliage so just a few inches remain above the ground. You can now see where your bulbs are without too much interference. If the foliage remained, you would not be able to see where you are digging.
Use a garden fork and dig straight down about 6 inches around the entire perimeter of the first plant (stay a couple inches away from the stem). Asiatic lilies are typically planted about 3 to 4 inches deep but digging 6 inches will ensure you clear the bulbs. Pull down on the handle of the garden fork in several places to lift the bulb out of the soil.
Dig up the remaining plants. Use the depth of the first bulb to determine how deep you need to dig for the rest of the bulbs. For instance, if the first bulb was 3 inches below the ground, then you only need to dig about 5 inches. On the other hand, if the first bulb was 6 inches deep, you need to dig around 8 inches below the soil.
Replant your Asiatic bulbs immediately. Separate any attached bulbs with your hands (do not use a knife). Plant the new bulbs in a prepared planting bed that has been tilled 12 inches deep and contains several inches of organic matter (e.g., compost). The bulbs should be 3 to 4 inches below the soil with the tips facing up and spaced 8 inches apart. Pack down the soil and water well.