Within 18 months of World War I beginning, cotton was a big problem for the Allies: They didn't have enough of it. And because it was used to dress battlefield wounds, that made the situation a life-threatening one. Doctors found their answer in moss, reports Smithsonian magazine in a look at the plant's remarkable properties—specifically, two species of sphagnum, which is peat moss that thrives in damp, cool climates. The star-shaped plant, it turns out, has been a human ally for at least 1,000 years. Native Americans used the highly absorbent, deodorizing plant as a sort of natural diaper for their infants, while there is Gaelic-Irish record of moss being used to pack wounds 1,000 years ago.
And Germans understood the potential of sphagnum dressings: So wrote a Scottish surgeon and botanist in a late-1914 anonymous article for the Scotsman that a 2013 paper gives credit for turning the Allies on to S. papillosum and S. palustre. The moss species grow rampant in Scotland and worked exceptionally well to both stanch bleeding and heal wounds by keeping the pH level around the wounds low. And because 90% of its cells are dead and thus empty, it can soak up roughly 20 times its own weight in liquid—blood, pus, or other bodily fluids—which is twice as much as cotton. Millions of moss dressings and pads were used by both sides throughout the war, much of it collected through "moss drives" held in several countries. Read Smithsonian's full piece, which explains why moss bandages aren't currently used, here.