Peace lilies, also known as Spathiphyllum, can be kept indoors or outdoors, and are more likely to bloom in a setting with indirect natural light, or fluorescent light and cool temperatures. Peace lilies are also more likely to flower when their roots and leaves have room to grow. They are capable of blooming year-round, most often during the spring and summer months.
Peace lilies thrive in cool environments with low humidity and medium to low light. Most importantly, they need the proper amount of light to produce blooms. Direct sunlight can cause the leaves to burn, so HGTV.com recommends placing the plant in a windowsill facing northward, or within a few feet of a window that receives bright sunlight. If the lily is outdoors, place it in a cool area with indirect light.
Even though peace lilies don't require a lot of watering, check the moisture of the soil once a week, especially during the warmer months when the plant may dry out more quickly. Over-watering can cause the leaves to turn brown and wither. Under-watering can cause the leaves to turn dark green and droop.
If the leaves are restricted and unable to spread out, move the peace lily to a larger container. A pot that is two inches wider will allow ample space for roots to expand.