Peace lilies (Spathiphyllum), also known as closet plants, are a popular choice for offices and homes. The peace lily is a flowering tropical plant from the Spathiphyllum genus. Outside of its hardiness zones, many people grow the peace lily indoors. There are many types of peace lilies within the genus. But in general, peace lilies have large, glossy, oval leaves. They typically bloom in the spring, though that can vary when growing them as houseplants. A healthy peace lily might bloom twice a year, resulting in several months of flowers.