What is a Witches’ Broom? (The Truth About These "Bird Nests")

So, how does a tree end up growing a broom? It all comes down to a glitch in its biology. Normally, a tree's branches grow outward in an organized, beautiful pattern. But sometimes, that regular growth gets completely disrupted. Instead of a long, straight branch, dozens or even hundreds of tiny shoots suddenly sprout out from a single point all at once. They crowd together, creating a thick, bushy clump that looks like the bristles of an old broom. What causes this sudden cellular chaos? The culprits are usually tiny, invisible invaders. Fungi are the most common troublemakers. They infect the wood and literally hijack the tree’s growth hormones. For example, a specific fungus called Taphrina betulina loves to target birch trees, creating massive, spectacular brooms. But it isn't just fungi. Viruses, bacteria, tiny mites, and even parasitic plants like dwarf mistletoe can mess with the tree's internal coding. Sometimes, it is just a simple, random genetic mutation. See More