Asiatic lilies are among the hardiest of all the hybrid lilies. They can be found in a wide range of colors and color combinations and are among the first lilies to bloom in the late spring and early summer. While, once established, Asiatic lilies are relatively easy-care and disease resistant, correct planting and care after the blooms are spent are essential to ensuring that your Asiatic lilies will keep blooming year after year.
Choose an area in full sun. Almost all types of lilies, and Asiatics are no exception, require at least 6-8 hours of full sun each day; therefore, you need to pick a sunny site in which to plant your lilies.
Use humus-rich soil. Asiatic lilies require humus-rich, fertile soil. Compost is best. However, if you do not have your own compost available or cannot find bags of compost at your local gardening center, you can work lots of organic matter, such as dry leaves and grass clippings as well as some organic mulch, into the soil in your planting bed. The soil should feel “fluffy” once the organic matter has been added.
Make sure your Asiatic lilies have “cool feet.” Asiatic lilies, like most lilies, like to have what gardeners call “cool feet.” In other words, the roots should be protected from the hot sun that the blooms of the lilies love so much. This means that you should plant your bulbs about 6 inches deep. Another good thing to do is to plant your Asiatic lilies with other perennials, which will help to shade the root systems of the lilies.
Apply a slow-release, balanced fertilizer after planting your bulbs. Follow the directions on the package of the fertilizer that you choose. There is no need to fertilize again during the growing season.
Spread mulch over your Asiatic lilies. Once planted, place 2-3 inches of any type of organic mulch over the planting area.
Water deeply about once a week. Asiatic lilies are relatively drought tolerant. You need to only water them once a week. Set your sprinkler to water your lilies for 20-30 minutes. This length of time allows the lilies to receive a deep drink of water -- at least one inch, which encourages deep rather than shallow roots. (Deep roots ensure that the lily has a firm foundation and that the roots remain cool.)
Do not cut back the stems immediately after the blooms are spent. This is probably the most important thing that you can do in order to insure that your Asiatic lilies will bloom the next year. The lilies take in nutrients through the stems and store these nutrients for the next year in the bulbs. You want the stems and leaves to die completely before cutting them back, which is usually in the early fall.