It makes the ground squishy. Sphagnum cristatum has stems that are upright. They reach five to fifteen centimetres in height. Branches are arranged in clusters around the stem. The leaves are small and overlapping. They have large, dead, water-holding cells. These hyaline cells give the moss its remarkable capacity to absorb and retain water. The colour is pale green to yellowish-green. Sometimes there is a hint of pink or red. It forms dense, spongy mats. They can cover hectares of wetland. They hold water like a giant sponge. It is the moss of the squishy ground. The one that makes your feet sink. What makes it special is the water-holding capacity. Sphagnum bog moss can hold up to twenty times its dry weight in water. It is a living sponge. It absorbs and retains moisture like no other plant. The secret is in the leaves. They are made of two types of cells. Large, dead, water-holding cells and small, living, green cells. The hyaline cells have pores. They draw in water through capillary action. They hold it like a tank. The chlorophyllose cells do the photosynthesis. It is the moss of the wetland. The one that builds its own habitat. The sphagnum bog moss also acidifies the water around it. It releases hydrogen ions in exchange for nutrients. This makes the environment more acidic. The acidity slows down the decomposition of organic matter. Peat accumulates. Over thousands of years, sphagnum bogs can build up layers of peat many metres thick. It is the moss of deep time. The one that has been building bogs for millennia. Biologically, the sphagnum bog moss reproduces by spores. They are released from capsules on short stalks. It also reproduces by fragmentation. Pieces broken off can grow into new plants. To find sphagnum bog moss is to find the spongy ground. It is soft, wet, and spongy. A living sponge under your feet. You can press your hand into it. You feel the water squish up around your fingers. It is the moss of the wetland. The one that holds water like a grudge. It builds entire wetlands doing it. It proves that the most humble plants can shape the landscape. No recorded Māori name distinguishes the sphagnum bog moss from other mosses. Mosses were generally called pūkohu or rimu. The spongy, water-holding moss of the wetlands would have been noticed. It was a source of water. A place of eels. A sign of the deep bog. No distinct name survives. The sphagnum bog moss was sometimes used as a dressing for wounds. Its remarkable water-holding capacity and natural antibacterial properties made it an ideal bandage. It was also used as a diaper material and as a lining for hangi ovens.