Witch's Broom: A Plant Deformity
Witch's broom (also witches' broom) is a deformity found on woody plants that changes their natural structure. A dense mass of shoots grows from a single point, distinctly resembling a broom. The causes are various: pathogens, fungi, insects, nematodes or a phytohormone that interferes with bud formation.
Mistletoe can be responsible for the formation of witch's broom. It's a parasite that attaches itself to the plant's branches so it can share its water and nutrients. The formation occurs around these infested areas. The broom growths typically last for the life of the host plant.