Even a rock-filled bed provides good drainage. Waterlogged soil with poor drainage will rot the bulbs, killing the plants. In addition to growing lilies in-ground, they are excellent subjects for container gardening. Botrytis is a fungal infection that can plague lilies and is best prevented by good air circulation Lilies can suffer from viral diseases, spread by aphids. Wash them off with water spray, or kill them with soap or chemical pesticide.
Slugs are partial to the flower tepals.
Just don t let them get the best of the lilies. Voles and shrews eat lily bulbs. To foil them, let the soil surface freeze before mulching lilies to minimize the chance of rodents tunneling their way toward the bulbs. It may also help not to use bone meal or blood meal, both of which attract rodents. Spring planting can be done as soon as the ground is workable, perhaps as early as mid- or late April.