Asiatic lilies require well-drained soils, as too much moisture in the soil can cause root rot and death. Avoid planting the bulbs in beds prone to standing water after rain, snow melt or irrigation. Working compost or peat moss into the soil prior to planting helps improve the drainage in poorer soils. Overly sandy soils that drain too quickly are not suitable for Asiatic lilies, as these plants do not bloom as well when under water stress.
Most Asiatic lilies are planted in the fall. After planting new bulbs, water the lily bed thoroughly so it's moistened to a 6-inch depth. Continue to water as needed to maintain the moisture in the soil until the ground begins to freeze. Resume watering in spring, once new growth appears. Generally, if the soil feels dry at a 1-inch depth, the lilies require irrigation. In the heat of summer this can be as often as every two to three days.
Avoid overhead watering as wet Asiatic lily foliage is more prone to mildews and other disease problems. Instead, water at the base of the plants so the moisture penetrates into the soil. This also helps prevent rapid moisture evaporation in the soil surface since the water reaches the roots more quickly. Provide water in the morning so any moisture that does splash onto the lily leaves has time to dry before nightfall, as mildews are more likely to grow on wet foliage in the cooler nighttime hours.
Use mulch to help retain moisture in the lily bed. A 2- to 3-inch mulch layer inhibits evaporation so that the lilies require less watering and are less prone to drying out. Apply the mulch in spring once new growth begins, then replenish the mulch layer in late summer or early fall. Mulch also keeps the soil cooler during the hot summer months and insulates it from extreme cold in the winter.