In World War I, the number of wounded soldiers was overwhelming for every participating army. Poor conditions and the difficulty of evacuation meant that many wounds became septic. There just weren't enough bandages, and nothing could be kept sterile. So battlefront doctors had to get creative. They began to dress wounds with peat moss! Peat, or sphagnum moss, was not only plentiful, but it was super-absorbent: the moss can hold up to 22 times its weight in liquid.
Sphagnum moss also has antiseptic properties. The plant’s cell walls are composed of special sugar molecules that “create an electrochemical halo around all of the cells, and the cell walls end up being negatively charged,” Kimmerer says. “Those negative charges mean that positively charged nutrient ions [like potassium, sodium and calcium] are going to be attracted to the sphagnum.” As the moss soaks up all the negatively charged nutrients in the soil, it releases positively charged ions (protons) that make the environment around it acidic.
For bogs, the acidity has remarkable preservative effects—think bog bodies—and keeps the environment limited to highly specialized species that can tolerate such harsh environments. For wounded humans, the result is that sphagnum bandages produce sterile environments by keeping the pH level around the wound low, and inhibiting the growth of bacteria.
Moss worked so well that volunteers back home held drives to gather and pack it for medical use. Read more about the wartime medical use of sphagnum moss at Smithsonian.