What is "witch's broom"

n. A disease or deformity in a woody plant, typically a tree, where the natural structure of the plant is changed so that a dense mass of shoots grows from a single point.

A witch's broom or witches' broom is a disease or deformity in a woody plant, typically a tree, where the natural structure of the plant is changed. A dense mass of shoots grows from a single point, with the resulting structure resembling a broom or a bird's nest.

Witch-broom disease caused by phytoplasmas is economically important in a number of crop plants, including the cocoa tree Theobroma cacao, jujube (Ziziphus jujuba) and the timber tree Melia azedarach.