Plant lily bulbs in the ground between mid-September and mid-October. The bright, colorful lily flowers bloom in early to late summer. Plant lily bulbs in loose, well-draining soil. Heavy, wet soil will cause the bulb to rot before the next season's growth begins. A soil pH of 6.5 is ideal for growing lilies, according to Iowa State University. (See reference 1) Lily flowers need six to eight hours of full sun each day.
Dig a hole 6 to 8 inches deep, or three times as deep as the height of the bulb. Plant lily bulbs 12 inches apart. Space groups of three to five bulbs 5 feet apart for a pleasing arrangement.
Place one bulb in each hole with the pointed end up and the round, bulbous end down. Cover with soil and pat firmly. Water the area until the soil is damp to a depth of 6 inches.
Spread a 3- to 4-inch layer of mulch over the planted bulbs. Organic straw, untreated grass clippings or shredded leaves work well. Spread mulch in late fall before the first hard freeze.
Pull back the mulch layer in the spring after the danger of frost has passed. Work carefully to avoid damaging any early starting lily shoots.
Apply an application of phosphorous-rich fertilizer in the spring. The University of Minnesota Extension recommends a slow-release 5-10-10 fertilizer.
Deadhead flowers when they are passing their prime. Leave green foliage on the plant until it dies back in winter, then remove it with sharp pruning shears.