True lilies (Lilium spp.) grow as outdoor garden plants from a bulb structure that fuels the perennial flowers. Most lilies thrive in U.S. Department of Agriculture plant hardiness zones 4 through 9, although some varieties are hardier than others. The stately flowers bloom during the summer and sometimes into fall when you use proper care strategies.
Lilies need loose, well-drained soil that's also rich in organic matter for the healthiest growth and flowering. A site with a soil pH near 6.5, determined by a soil test, provides the optimum acidity. Lilies also perform better when they receive at least six hours of daily sunlight. Digging a 2-inch layer of compost into the soil prior to planting improves the site's organic content. When planting lilies, sow the bulbs 6 to 8 inches deep and space them 8 to 12 inches apart.
Fertilizer and Water
Spring fertilization replenishes the nutrients in the soil for the lilies. Apply a 5-10-10 or similar slow-release fertilizer when new shoots emerge. Use the amount of fertilizer recommended on the package for your garden size and spread it around the lily plants, about 6 inches away from the base of the stems. Water the lilies after fertilization so the nutrients can soak into the soil. Lilies require about 1 inch of water, either from rainfall or irrigation, for healthy growth. A 2-inch mulch layer helps retain moisture while also preventing weeds and insulating the soil.
Pruning and Division
Seed production can reduce flowering on lilies. Deadheading, or cutting off the spent blooms, prevents seeds from forming and helps the plants look more attractive. Only prune off lily leaves after they die naturally, even if the plant has stopped flowering for the year. The bulbs require division about every three years, or when the clumps become crowded and begin flowering poorly. Dig up the bulbs after the foliage dies back in fall and separate them. Replant the divided bulbs at the proper spacing and depth.
Most lily problems are caused by improper watering. Wet foliage and flowers can cause Botrytis blight and other fungal diseases. Avoid overhead watering and irrigate in the morning so the foliage can dry quickly. Treating fungal problems promptly with a fungicide prevents the spores from spreading. Aphids can also spread fungal and viral diseases. Treat aphids by spraying the affected plants with an insecticidal soap. You may need to reapply the soap every three days for a week or two to completely control the pest population.
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