Plant of the Month: Peace Lily (Spathiphyllum) A long-time favorite among house plant enthusiasts, research conducted by NASA found the Peace Lily to be one of the top indoor plants for cleaning air. This tropical plant breaks down and neutralizes toxic gases like benzene, formaldehyde, and carbon monoxide.Peace lilies, Spathiphyllum, are member of the philodendron family and native to the South America and Central American regions. The most common peace lily houseplant is the Clevelandii which consists of long green foliage that grows directly from the soil. Plants bloom with white flowers on long stalks. As a houseplant the peace lily offers much more than color and texture. These plants grow 1 to 4 feet tall with equal width.