Lilies are bulbous plants that are planted in the fall or early spring and bloom during the late spring and summer months. Lilies require amended soil and good water drainage, and in areas where the soil contains a lot of clay, the technique of mounding--also called hilling--will improve water drainage. Mounding also helps support tall plants such as lilies, especially if they are planted in areas with high winds.
Till the planting site to a depth of 12 inches. Mix in compost, humus or peat moss so that the planting bed consists of 2/3 the original soil and 1/3 the new organic matter. This will produce extra soil to mound the plants.
Plant lily bulbs with the tips facing up about 2 inches shallower than the label directs; usually 2 to 4 inches will suffice. Space the bulbs 12 to 18 inches apart.
Backfill the soil and pack it down lightly to remove pockets of air.
Create a round, pyramid-shaped mound on top of the planting site with the extra soil from Step 1. The mound should be 2 inches tall and have a flat top that is about 3 inches in diameter. The bottom of the mound should be 8 to 10 inches in diameter.