Terrarium moss provides containerized plants with the conditions they need to thrive in a closed environment. Terrarium moss, also called peat moss or sphagnum moss, is combined with perlite and soil to create a water retaining growing medium. This medium is responsible for the health of each member of the terrarium's ecosystem. In nature terrarium moss grows in northern climates. There is no listed USDA hardiness zone for this plant, since it is often grown in the wild and harvested. However, it prefers cooler climates, boggy areas and a great deal of moisture. When sphagnum moss is harvested, it can be taken off the surface of bogs where it creates large, thick mats capable of supporting a great deal of weight without sinking. The mats are essentially large sponges that are formed from the moss' capillary system of roots and small leaves. Considering how well the moss retains water, it makes sense for it to provide and recirculate water throughout a terrarium's closed space. In addition, terrarium moss raises the soil's acidity. This is beneficial for a number of plants. When planning a terrarium, choose plants that benefit from high acidity like African violets and orchids. Even when not in a terrarium, these plants benefit from terrarium moss as a growing medium or soil additive. The moss used in terrariums is no longer living. It releases moisture and acidity during its decomposition process. To care for living moss, a grower places sphagnum moss clippings in a flat box and maintains high levels of moisture. Most growers cultivate terrarium moss as a medium for other plants, but it has greenery and landscape merit in ponds and watery areas. Industrial sphagnum growers expect to cultivate a significant harvest within eight years of planting. Those not planting for an industrial crop, see harvests in a shorter time.