Summarize:

A deep pot is essential for growing healthy Asiatic lilies in a container. Go for a container with a diameter of at least nine inches (23 cm) and a depth of eight inches (20 cm) or more. A pot at this minimum size can accommodate one large bulb with a diameter of four to five inches (10 to 12 cm) or three to four smaller bulbs with diameters less than three inches (eight cm). Before filling the pot with soil, you’ll need to add a layer of drainage material. Spread two inches (five cm) of small rocks, gravel, or another suitably loose material at the base of the pot. If you’ve recently broken a pot, you can use its pieces for part of your drainage layer. Asiatic lilies aren’t terribly fussy about their soil, but it does need to drain well. For best results, look for a potting soil labeled for lilies at your local garden center or nursery. If you have soil on hand that feels too moist and dense, mix four parts of it with one part peat moss or horticultural grit. Roughly measure or estimate the height of the bulb or bulbs you’re planting. Dig a hole at least twice as deep as bulbs’ approximate height. That way, you’ll be able to cover each bulb with a soil depth equal to its height, measuring from the top. If you’re planting more than one bulb, space them about two inches (five cm) apart. If you’re keeping your container indoors, choose a spot less than three feet away from a window. It should receive six to eight hours of direct sunlight. If you’re keeping your container outdoors, choose a well-lit area that won’t get drenched in rain. Go for a covered area or a spot in a wall’s rain shadow. Potted lilies shouldn’t be kept in warm indoor environments all year long. You can keep indoor plants in their pots until the late fall, then plant them in your outdoor garden. If your location doesn’t experience cool winters, consider overwintering Asiatic lilies in a cooler set to a temperature of about 40 degrees Fahrenheit (4.4 degrees Celsius).
Choose a deep container for healthy plants. Place a layer of drainage material at the bottom of the container. Fill the container with well-draining potting soil. Plant a group of bulbs at least as deep as their height. Place your container in a well-lit area. Transfer potted lilies to the garden or a cool area for overwintering.