Lilies self propagate. In several years one bulb has turned into many and your garden is crowded. If your lilies don't bloom as much as before, it's time to transplant some of them. This is best done in the fall or early winter when the bulbs are less likely to experience shock and after the foliage has withered, making the bulbs easier to dig up and handle. If necessary, the bulbs, green plant and all can be transplanted during the growing season.
Dig out the entire plant during the growing season or just the bulbs after the foliage has yellowed (cut down to several inches above the ground). Dig straight down about 8 inches around the perimeter of plant. Then pull up on the handle of the shovel or garden fork in several places to lift the bulbs out of the ground. Shake off any excess dirt.
Select a new planting site that is in full sun or partial shade. Lilies prefer full sun but can tolerate an area that receives sunlight for only half a day.
Prepare the soil so that it drains well. If you're not sure if the soil is adequately draining, dig a hole 2 feet deep and fill it with water. If water remains after 24 hours, the soil needs amending. Till about 3 inches of organic matter such as peat moss or compost into the top 12 inches of the planting bed.
Transplanting a whole plant at same depth as it was before. When transplanting bulbs, plant them so that the tops are about 4 to 6 inches below the soil's surface and space them 6 inches apart.
Firm down the soil with you hands or feet to remove air pockets that could expose the root to risk of rot. Water the area and push down on the soil a second time.