A witch's broom plant is a tree or woody herb with a deformity of its branches that resembles the dense arrangement of straw in a crudely made broom. Witch's brooms can be caused by disease, by physical breakage or by genetic mutations.
Some plants that are prone to developing witch's brooms are oaks, pecans, pines and peach trees. Conifers often develop witch's brooms in reaction to being parasitized by dwarf mistletoe. Witch's brooms can continue to grow and be displayed as dwarf plants if cut down from their branch and grafted onto a compatible root system. They are collected by enthusiasts and can develop into dwarf cultivars, or strains, of the tree species if propagated. If they are due to mutation, they can even be bred.