A witch's broom is an unusually dense and compact cluster of twigs and foliage formed on a woody plant. The mass of shoots comes from a common point, giving the growth a broom-like appearance.
Witches' brooms can be caused by various sources including mites, viruses, fungi, mistletoes, insects, and nematodes. Knowing the type of host plant can help determine the cause of the witch's broom. Witches' brooms can also be caused by a genetic mutation in a plant. These "mutant brooms" are particularly important commercially because their new genetic makeup can lead to new plant cultivars.
Herbicide damage is also a common cause of witches’ broom. Round-Up™ is not one of the chemicals that creates the damage. When other chemicals are combined with the glyphosate for longer-lasting control and used for edging landscape beds, If used on a consistent basis, the chemicals seep into the ground and are absorbed by the roots. Although, at first glance, it may seem like the herbicide is being correctly applied since many of these products are labeled for use in graveled areas, driveways, and sidewalks; the label also states they should not be applied within the root zone of desirable plants.
Leonard-Mularz, Michelle. “What Is Witch’s Broom.” UF/IFAS Extension Monroe County, 12 Nov. 2021, blogs.ifas.ufl.edu/monroeco/2021/11/12/what-is-witchs-broom/. Accessed 1 Oct. 2023.
Communications, IFAS. “Witch’s Broom - Institute of Food and Agricultural Sciences - University of Florida, Institute of Food and Agricultural Sciences - UF/IFAS.” Programs.ifas.ufl.edu, 2018, programs.ifas.ufl.edu/florida-4-h-forest-ecology/forest-ecology-contest/contest-stations/forest-health/stresses/witchs-broom/. Accessed 2 Oct. 2023.
Photo credit: UF/IFAS Monroe County Extension