Japanese barberry is a dense, deciduous, spiny shrub that grows 2 to 8 ft. high. It forms dense stands in widely varied natural habitats and alters soil pH, nitrogen levels, and biological activity in the soil. Once established, barberry displaces native plants and reduces wildlife habitat and forage. Learn more from the NPS website. Japanese barberry is prohibited in New York; it is illegal to purchase, sell, transport or propagate.