Providing light, warmth or water -- or simply having patience -- may be all that's needed to encourage a peace lily (Spathiphyllum spp.) to flower. This glossy leaved, perennial plant is usually grown as a houseplant, though it grows outdoors year-round in U.S. Department of Agriculture plant hardiness zones 11 and 12. Peace lily flowers are white and appear intermittently.
Improving Light Levels
A peace lily tolerates low light conditions, but very low light may prevent the plant from flowering. The best light for blooms is bright, indirect light.
Place a peace lily houseplant in an area of the home where it's bright enough to read a newspaper, and in summer place the plant outdoors in shade. Don't grow this plant in a full-sun site or direct light indoors because this causes scorching. Grow an outdoor peace lily in a partial-shade or bright shade site.
Peace lily leaves can accumulate dust indoors, which prevents light from reaching the plant. Wipe a dusty peace lily's leaves with a soft, clean, damp cloth.
Steady, warm temperatures promote good growth and flowering in a peace lily. This plant grows best at temperatures from 68 to 85 degrees Fahrenheit during the day and 10 degrees lower at night. Temperatures in the 40s and 50s slow down growth and flowering.
Grow an outdoor peace lily in an area sheltered from winds, and don't place an indoor peace lily in a drafty spot. In winter, place a peace lily houseplant in a warm, bright room but away from direct heat. Mist the plant every other day with a fine spray to maintain humidity. Alternatively, place the plant in its drip tray on a tray of pebbles filled with water.
Watering a Peace Lily
Increasing water sometimes encourages a peace lily to flower. A peace lily needs constantly moist soil. The container for this plant must have drainage holes.
Water a peace lily when the soil or potting mix surface is dry. Allow water to stand until it reaches room temperature when watering a peace lily. Water an outdoor plant until the water puddles on the soil surface, and water a peace lily in a container until water flows through the drainage holes. Don't allow a peace lily to become so dry that the leaves wilt, and don't water so much that the soil becomes soggy. (Ref 1)
Pruning and Waiting
Pruning a peace lily's faded flowers encourages the plant to rebloom. When a peace lily's flowers fade, wipe pruning shear blades with a cloth that was dipped in rubbing alcohol, and prune the flowers at the base of their stems. Wipe the pruning shears again when you've finished.
If your peace lily has never flowered, it may simply be too young. A newly bought plant may take up to one year to grow large enough to flower. On the other hand, older plants flower less well than young ones. If your peace lily is 4 or 5 years old or older, consider discarding the plant and buying another.