Can You Cut Lilies Down After They Bloom?

True lilies, those in the genus Lilium, are graceful, elegant plants that flower on vertical, leafy stems. These stems die down in the winter, but the bulb that survives the cold months deep underground depends on the leaves to produce the food it stores for the next year. Cutting too much of the stem before it turns completely yellow will reduce the vigor of the lilies in the following year.

Although many flowers such as daylilies and water lilies have "lily" as part of their name, only true lilies have the stiff, leafy stems and scaly bulbs that mark the genus Lilium. Some varieties grow up to 7 feet tall, and every year the clump produces more shoots. Many lilies grow roots from the part of the stem that is located between the bulb and the top of the ground, as well as from the base of the bulb. These roots have the unique property of being able to pull the bulb deeper into the soil if needed. Lily blossoms usually have six petals and may be pendant, trumpet-shaped or upward-facing.

Lilies are not difficult to grow, but they do need constant moisture with good drainage. Dig in extra organic matter such as compost or well-rotted manure before planting bulbs in the spring or fall. Give lilies full sun except in hot summer areas, where some shade is appreciated. An ideal situation is among shrubs so the lily stems can reach into the light, but the roots are cool. Feed with a slow-release fertilizer when the stems are 6 to 10 inches high and again as flower buds develop. After flowering, remove the spent cluster above the leaves, but let the stem stand until it dies in the fall. Then you can cut it back, leaving 5 or 6 inches to mark its place.

A virus disease, lily mosaic, can cause mottling of the leaves and death of the plant. It is spread by aphids, so any affected lilies should be removed as soon as possible. Buy bulbs only from reputable suppliers to avoid contamination. Tiger lilies are often carriers of the virus and should not be grown with modern hybrids unless you're sure they're virus-free. Two fungal diseases, botrytis blight and basal rot, may also be a problem, but given good drainage and care, your lilies should stay disease-free.

Lilies look lovely almost anywhere, but perennials or low shrubs give some fullness to the narrow, somewhat bare stems. The back of a flower border is an excellent place for lilies, as is a naturalistic garden with azaleas and rhododendrons. Lilies also do well in large pots and can provide a colorful focal point when in bloom. After the flowers fade, you can move them to an out-of-the-way location.