There are several places in Scotland, England, and Ireland where the trees are wrapped with rags. These are clootie wells, forests with mineral springs that are believed to have healing powers. A relic of ancient paganism, the idea is that if you have an ailment, you should wash the afflicted area in water from these springs. Then you tie the rag you used around a tree, and as the rag rots, your ailment will disappear. You can see the problem here: Cotton and wool rags may take years to rot, but polyester can take centuries, which means more and more rags survive longer and damage the forest. But it’s terrible luck to remove them. Read more about this ancient practice at Atlas Obscura.